text: // @flow strict-local
  
  import type {
    GraphVisitor,
    FilePath,
    Symbol,
    TraversalActions,
  } from '@parcel/types';
  import type {NodeId, SerializedContentGraph} from '@parcel/graph';
  
  import type {
    Asset,
    AssetNode,
    Bundle,
    BundleGraphNode,
    BundleGroup,
    Dependency,
    DependencyNode,
    InternalSourceLocation,
    Target,
  } from './types';
  import type AssetGraph from './AssetGraph';
  import type {ProjectPath} from './projectPath';
  
  import assert from 'assert';
  import invariant from 'assert';
  import nullthrows from 'nullthrows';
  import {ContentGraph, ALL_EDGE_TYPES, mapVisitor} from '@parcel/graph';
  import {Hash, hashString} from '@parcel/hash';
  import {objectSortedEntriesDeep, getRootDir} from '@parcel/utils';
  
  import {Priority, BundleBehavior, SpecifierType} from './types';
  import {getBundleGroupId, getPublicId} from './utils';
  import {ISOLATED_ENVS} from './public/Environment';
  import {fromProjectPath} from './projectPath';
  
  export const bundleGraphEdgeTypes = {
    // A lack of an edge type indicates to follow the edge while traversing
    // the bundle's contents, e.g. `bundle.traverse()` during packaging.
    null: 1,
    // Used for constant-time checks of presence of a dependency or asset in a bundle,
    // avoiding bundle traversal in cases like `isAssetInAncestors`
    contains: 2,
    // Connections between bundles and bundle groups, for quick traversal of the
    // bundle hierarchy.
    bundle: 3,
    // When dependency -> asset: Indicates that the asset a dependency references
    //                           is contained in another bundle.
    // When dependency -> bundle: Indicates the bundle is necessary for any bundles
    //                           with the dependency.
    // When bundle -> bundle:    Indicates the target bundle is necessary for the
    //                           source bundle.
    // This type prevents referenced assets from being traversed from dependencies
    // along the untyped edge, and enables traversal to referenced bundles that are
    // not directly connected to bundle group nodes.
    references: 4,
    // Signals that the dependency is internally resolvable via the bundle's ancestry,
    // and that the bundle connected to the dependency is not necessary for the source bundle.
    internal_async: 5,
  };
  
  export type BundleGraphEdgeType = $Values<typeof bundleGraphEdgeTypes>;
  
  type InternalSymbolResolution = {|
    asset: Asset,
    exportSymbol: string,
    symbol: ?Symbol | false,
    loc: ?InternalSourceLocation,
  |};
  
  type InternalExportSymbolResolution = {|
    ...InternalSymbolResolution,
    +exportAs: Symbol | string,
  |};
  
  type SerializedBundleGraph = {|
    $$raw: true,
    graph: SerializedContentGraph<BundleGraphNode, BundleGraphEdgeType>,
    bundleContentHashes: Map<string, string>,
    assetPublicIds: Set<string>,
    publicIdByAssetId: Map<string, string>,
  |};
  
  function makeReadOnlySet<T>(set: Set<T>): $ReadOnlySet<T> {
    return new Proxy(set, {
      get(target, property) {
        if (property === 'delete' || property === 'add' || property === 'clear') {
          return undefined;
        } else {
          // $FlowFixMe[incompatible-type]
          let value = target[property];
          return typeof value === 'function' ? value.bind(target) : value;
        }
      },
    });
  }
  
  export default class BundleGraph {
    _assetPublicIds: Set<string>;
    _publicIdByAssetId: Map<string, string>;
    // TODO: These hashes are being invalidated in mutative methods, but this._graph is not a private
    // property so it is possible to reach in and mutate the graph without invalidating these hashes.
    // It needs to be exposed in BundlerRunner for now based on how applying runtimes works and the
    // BundlerRunner takes care of invalidating hashes when runtimes are applied, but this is not ideal.
    _bundleContentHashes: Map<string, string>;
    _targetEntryRoots: Map<ProjectPath, FilePath> = new Map();
    _graph: ContentGraph<BundleGraphNode, BundleGraphEdgeType>;
  
    constructor({
      graph,
      publicIdByAssetId,
      assetPublicIds,
      bundleContentHashes,
    }: {|
      graph: ContentGraph<BundleGraphNode, BundleGraphEdgeType>,
      publicIdByAssetId: Map<string, string>,
      assetPublicIds: Set<string>,
      bundleContentHashes: Map<string, string>,
    |}) {
      this._graph = graph;
      this._assetPublicIds = assetPublicIds;
      this._publicIdByAssetId = publicIdByAssetId;
      this._bundleContentHashes = bundleContentHashes;
    }
  
    static fromAssetGraph(
      assetGraph: AssetGraph,
      publicIdByAssetId: Map<string, string> = new Map(),
      assetPublicIds: Set<string> = new Set(),
    ): BundleGraph {
      let graph = new ContentGraph<BundleGraphNode, BundleGraphEdgeType>();
      let assetGroupIds = new Set();
      let assetGraphNodeIdToBundleGraphNodeId = new Map<NodeId, NodeId>();
  
      let assetGraphRootNode =
        assetGraph.rootNodeId != null
          ? assetGraph.getNode(assetGraph.rootNodeId)
          : null;
      invariant(assetGraphRootNode != null && assetGraphRootNode.type === 'root');
  
      for (let [nodeId, node] of assetGraph.nodes) {
        if (node.type === 'asset') {
          let {id: assetId} = node.value;
          // Generate a new, short public id for this asset to use.
          // If one already exists, use it.
          let publicId = publicIdByAssetId.get(assetId);
          if (publicId == null) {
            publicId = getPublicId(assetId, existing =>
              assetPublicIds.has(existing),
            );
            publicIdByAssetId.set(assetId, publicId);
            assetPublicIds.add(publicId);
          }
        }
  
        // Don't copy over asset groups into the bundle graph.
        if (node.type === 'asset_group') {
          assetGroupIds.add(nodeId);
        } else {
          let bundleGraphNodeId = graph.addNodeByContentKey(node.id, node);
          if (node.id === assetGraphRootNode?.id) {
            graph.setRootNodeId(bundleGraphNodeId);
          }
          assetGraphNodeIdToBundleGraphNodeId.set(nodeId, bundleGraphNodeId);
        }
      }
  
      for (let edge of assetGraph.getAllEdges()) {
        let fromIds;
        if (assetGroupIds.has(edge.from)) {
          fromIds = [
            ...assetGraph.inboundEdges.getEdges(
              edge.from,
              bundleGraphEdgeTypes.null,
            ),
          ];
        } else {
          fromIds = [edge.from];
        }
  
        for (let from of fromIds) {
          if (assetGroupIds.has(edge.to)) {
            for (let to of assetGraph.outboundEdges.getEdges(
              edge.to,
              bundleGraphEdgeTypes.null,
            )) {
              graph.addEdge(
                nullthrows(assetGraphNodeIdToBundleGraphNodeId.get(from)),
                nullthrows(assetGraphNodeIdToBundleGraphNodeId.get(to)),
              );
            }
          } else {
            graph.addEdge(
              nullthrows(assetGraphNodeIdToBundleGraphNodeId.get(from)),
              nullthrows(assetGraphNodeIdToBundleGraphNodeId.get(edge.to)),
            );
          }
        }
      }
  
      return new BundleGraph({
        graph,
        assetPublicIds,
        bundleContentHashes: new Map(),
        publicIdByAssetId,
      });
    }
  
    serialize(): SerializedBundleGraph {
      return {
        $$raw: true,
        graph: this._graph.serialize(),
        assetPublicIds: this._assetPublicIds,
        bundleContentHashes: this._bundleContentHashes,
        publicIdByAssetId: this._publicIdByAssetId,
      };
    }
  
    static deserialize(serialized: SerializedBundleGraph): BundleGraph {
      return new BundleGraph({
        graph: ContentGraph.deserialize(serialized.graph),
        assetPublicIds: serialized.assetPublicIds,
        bundleContentHashes: serialized.bundleContentHashes,
        publicIdByAssetId: serialized.publicIdByAssetId,
      });
    }
  
    addAssetGraphToBundle(
      asset: Asset,
      bundle: Bundle,
      shouldSkipDependency: Dependency => boolean = d =>
        this.isDependencySkipped(d),
    ) {
      let assetNodeId = this._graph.getNodeIdByContentKey(asset.id);
      let bundleNodeId = this._graph.getNodeIdByContentKey(bundle.id);
  
      // The root asset should be reached directly from the bundle in traversal.
      // Its children will be traversed from there.
      this._graph.addEdge(bundleNodeId, assetNodeId);
      this._graph.traverse((nodeId, _, actions) => {
        let node = nullthrows(this._graph.getNode(nodeId));
        if (node.type === 'bundle_group') {
          actions.skipChildren();
          return;
        }
  
        if (node.type === 'dependency' && shouldSkipDependency(node.value)) {
          actions.skipChildren();
          return;
        }
  
        if (node.type === 'asset' || node.type === 'dependency') {
          this._graph.addEdge(
            bundleNodeId,
            nodeId,
            bundleGraphEdgeTypes.contains,
          );
        }
  
        if (node.type === 'dependency') {
          for (let [bundleGroupNodeId, bundleGroupNode] of this._graph
            .getNodeIdsConnectedFrom(nodeId)
            .map(id => [id, nullthrows(this._graph.getNode(id))])
            .filter(([, node]) => node.type === 'bundle_group')) {
            invariant(bundleGroupNode.type === 'bundle_group');
            this._graph.addEdge(
              bundleNodeId,
              bundleGroupNodeId,
              bundleGraphEdgeTypes.bundle,
            );
          }
  
          // If the dependency references a target bundle, add a reference edge from
          // the source bundle to the dependency for easy traversal.
          if (
            this._graph
              .getNodeIdsConnectedFrom(nodeId, bundleGraphEdgeTypes.references)
              .map(id => nullthrows(this._graph.getNode(id)))
              .some(node => node.type === 'bundle')
          ) {
            this._graph.addEdge(
              bundleNodeId,
              nodeId,
              bundleGraphEdgeTypes.references,
            );
          }
        }
      }, assetNodeId);
      this._bundleContentHashes.delete(bundle.id);
    }
  
    addEntryToBundle(
      asset: Asset,
      bundle: Bundle,
      shouldSkipDependency?: Dependency => boolean,
    ) {
      this.addAssetGraphToBundle(asset, bundle, shouldSkipDependency);
      if (!bundle.entryAssetIds.includes(asset.id)) {
        bundle.entryAssetIds.push(asset.id);
      }
    }
  
    internalizeAsyncDependency(bundle: Bundle, dependency: Dependency) {
      if (dependency.priority === Priority.sync) {
        throw new Error('Expected an async dependency');
      }
  
      this._graph.addEdge(
        this._graph.getNodeIdByContentKey(bundle.id),
        this._graph.getNodeIdByContentKey(dependency.id),
        bundleGraphEdgeTypes.internal_async,
      );
      this.removeExternalDependency(bundle, dependency);
    }
  
    isDependencySkipped(dependency: Dependency): boolean {
      let node = this._graph.getNodeByContentKey(dependency.id);
      invariant(node && node.type === 'dependency');
      return !!node.hasDeferred || node.excluded;
    }
  
    getParentBundlesOfBundleGroup(bundleGroup: BundleGroup): Array<Bundle> {
      return this._graph
        .getNodeIdsConnectedTo(
          this._graph.getNodeIdByContentKey(getBundleGroupId(bundleGroup)),
          bundleGraphEdgeTypes.bundle,
        )
        .map(id => nullthrows(this._graph.getNode(id)))
        .filter(node => node.type === 'bundle')
        .map(node => {
          invariant(node.type === 'bundle');
          return node.value;
        });
    }
  
    resolveAsyncDependency(
      dependency: Dependency,
      bundle: ?Bundle,
    ): ?(
      | {|type: 'bundle_group', value: BundleGroup|}
      | {|type: 'asset', value: Asset|}
    ) {
      let depNodeId = this._graph.getNodeIdByContentKey(dependency.id);
      let bundleNodeId =
        bundle != null ? this._graph.getNodeIdByContentKey(bundle.id) : null;
  
      if (
        bundleNodeId != null &&
        this._graph.hasEdge(
          bundleNodeId,
          depNodeId,
          bundleGraphEdgeTypes.internal_async,
        )
      ) {
        let referencedAssetNodeIds = this._graph.getNodeIdsConnectedFrom(
          depNodeId,
          bundleGraphEdgeTypes.references,
        );
  
        let resolved;
        if (referencedAssetNodeIds.length === 0) {
          resolved = this.getResolvedAsset(dependency, bundle);
        } else if (referencedAssetNodeIds.length === 1) {
          let referencedAssetNode = this._graph.getNode(
            referencedAssetNodeIds[0],
          );
          // If a referenced asset already exists, resolve this dependency to it.
          invariant(referencedAssetNode?.type === 'asset');
          resolved = referencedAssetNode.value;
        } else {
          throw new Error('Dependencies can only reference one asset');
        }
  
        if (resolved == null) {
          return;
        } else {
          return {
            type: 'asset',
            value: resolved,
          };
        }
      }
  
      let node = this._graph
        .getNodeIdsConnectedFrom(this._graph.getNodeIdByContentKey(dependency.id))
        .map(id => nullthrows(this._graph.getNode(id)))
        .find(node => node.type === 'bundle_group');
  
      if (node == null) {
        return;
      }
  
      invariant(node.type === 'bundle_group');
      return {
        type: 'bundle_group',
        value: node.value,
      };
    }
  
    getReferencedBundle(dependency: Dependency, fromBundle: Bundle): ?Bundle {
      let dependencyNodeId = this._graph.getNodeIdByContentKey(dependency.id);
  
      // If this dependency is async, there will be a bundle group attached to it.
      let node = this._graph
        .getNodeIdsConnectedFrom(dependencyNodeId)
        .map(id => nullthrows(this._graph.getNode(id)))
        .find(node => node.type === 'bundle_group');
  
      if (node != null) {
        invariant(node.type === 'bundle_group');
        return this.getBundlesInBundleGroup(node.value, {
          includeInline: true,
        }).find(b => {
          let mainEntryId = b.entryAssetIds[b.entryAssetIds.length - 1];
          return mainEntryId != null && node.value.entryAssetId === mainEntryId;
        });
      }
  
      // Otherwise, it may be a reference to another asset in the same bundle group.
      // Resolve the dependency to an asset, and look for it in one of the referenced bundles.
      let referencedBundles = this.getReferencedBundles(fromBundle, {
        includeInline: true,
      });
      let referenced = this._graph
        .getNodeIdsConnectedFrom(
          dependencyNodeId,
          bundleGraphEdgeTypes.references,
        )
        .map(id => nullthrows(this._graph.getNode(id)))
        .find(node => node.type === 'asset');
  
      if (referenced != null) {
        invariant(referenced.type === 'asset');
        return referencedBundles.find(b =>
          this.bundleHasAsset(b, referenced.value),
        );
      }
    }
  
    removeAssetGraphFromBundle(asset: Asset, bundle: Bundle) {
      let bundleNodeId = this._graph.getNodeIdByContentKey(bundle.id);
      let assetNodeId = this._graph.getNodeIdByContentKey(asset.id);
  
      // Remove all contains edges from the bundle to the nodes in the asset's
      // subgraph.
      this._graph.traverse((nodeId, context, actions) => {
        let node = nullthrows(this._graph.getNode(nodeId));
  
        if (node.type === 'bundle_group') {
          actions.skipChildren();
          return;
        }
  
        if (node.type !== 'dependency' && node.type !== 'asset') {
          return;
        }
  
        if (
          this._graph.hasEdge(bundleNodeId, nodeId, bundleGraphEdgeTypes.contains)
        ) {
          this._graph.removeEdge(
            bundleNodeId,
            nodeId,
            bundleGraphEdgeTypes.contains,
            // Removing this contains edge should not orphan the connected node. This
            // is disabled for performance reasons as these edges are removed as part
            // of a traversal, and checking for orphans becomes quite expensive in
            // aggregate.
            false /* removeOrphans */,
          );
        } else {
          actions.skipChildren();
        }
  
        if (node.type === 'asset' && this._graph.hasEdge(bundleNodeId, nodeId)) {
          // Remove the untyped edge from the bundle to the node (it's an entry)
          this._graph.removeEdge(bundleNodeId, nodeId);
  
          let entryIndex = bundle.entryAssetIds.indexOf(node.value.id);
          if (entryIndex >= 0) {
            // Shared bundles have untyped edges to their asset graphs but don't
            // have entry assets. For those that have entry asset ids, remove them.
            bundle.entryAssetIds.splice(entryIndex, 1);
          }
        }
  
        if (node.type === 'dependency') {
          this.removeExternalDependency(bundle, node.value);
          if (
            this._graph.hasEdge(
              bundleNodeId,
              nodeId,
              bundleGraphEdgeTypes.references,
            )
          ) {
            this._graph.addEdge(
              bundleNodeId,
              nodeId,
              bundleGraphEdgeTypes.references,
            );
          }
          if (
            this._graph.hasEdge(
              bundleNodeId,
              nodeId,
              bundleGraphEdgeTypes.internal_async,
            )
          ) {
            this._graph.removeEdge(
              bundleNodeId,
              nodeId,
              bundleGraphEdgeTypes.internal_async,
            );
          }
        }
      }, assetNodeId);
  
      // Remove bundle node if it no longer has any entry assets
      if (this._graph.getNodeIdsConnectedFrom(bundleNodeId).length === 0) {
        this.removeBundle(bundle);
      }
  
      this._bundleContentHashes.delete(bundle.id);
    }
  
    removeBundle(bundle: Bundle): Set<BundleGroup> {
      // Remove bundle node if it no longer has any entry assets
      let bundleNodeId = this._graph.getNodeIdByContentKey(bundle.id);
  
      let bundleGroupNodeIds = this._graph.getNodeIdsConnectedTo(
        bundleNodeId,
        bundleGraphEdgeTypes.bundle,
      );
      this._graph.removeNode(bundleNodeId);
  
      let removedBundleGroups: Set<BundleGroup> = new Set();
      // Remove bundle group node if it no longer has any bundles
      for (let bundleGroupNodeId of bundleGroupNodeIds) {
        let bundleGroupNode = nullthrows(this._graph.getNode(bundleGroupNodeId));
        invariant(bundleGroupNode.type === 'bundle_group');
        let bundleGroup = bundleGroupNode.value;
  
        if (
          // If the bundle group's entry asset belongs to this bundle, the group
          // was created because of this bundle. Remove the group.
          bundle.entryAssetIds.includes(bundleGroup.entryAssetId) ||
          // If the bundle group is now empty, remove it.
          this.getBundlesInBundleGroup(bundleGroup, {includeInline: true})
            .length === 0
        ) {
          removedBundleGroups.add(bundleGroup);
          this.removeBundleGroup(bundleGroup);
        }
      }
  
      this._bundleContentHashes.delete(bundle.id);
      return removedBundleGroups;
    }
  
    removeBundleGroup(bundleGroup: BundleGroup) {
      let bundleGroupNode = nullthrows(
        this._graph.getNodeByContentKey(getBundleGroupId(bundleGroup)),
      );
      invariant(bundleGroupNode.type === 'bundle_group');
  
      let bundlesInGroup = this.getBundlesInBundleGroup(bundleGroupNode.value, {
        includeInline: true,
      });
      for (let bundle of bundlesInGroup) {
        if (this.getBundleGroupsContainingBundle(bundle).length === 1) {
          let removedBundleGroups = this.removeBundle(bundle);
          if (removedBundleGroups.has(bundleGroup)) {
            // This function can be reentered through removeBundle above. In the case this
            // bundle group has already been removed, stop.
            return;
          }
        }
      }
  
      // This function can be reentered through removeBundle above. In this case,
      // the node may already been removed.
      if (this._graph.hasContentKey(bundleGroupNode.id)) {
        this._graph.removeNode(
          this._graph.getNodeIdByContentKey(bundleGroupNode.id),
        );
      }
  
      assert(
        bundlesInGroup.every(
          bundle => this.getBundleGroupsContainingBundle(bundle).length > 0,
        ),
      );
    }
  
    removeExternalDependency(bundle: Bundle, dependency: Dependency) {
      let bundleNodeId = this._graph.getNodeIdByContentKey(bundle.id);
      for (let bundleGroupNode of this._graph
        .getNodeIdsConnectedFrom(this._graph.getNodeIdByContentKey(dependency.id))
        .map(id => nullthrows(this._graph.getNode(id)))
        .filter(node => node.type === 'bundle_group')) {
        let bundleGroupNodeId = this._graph.getNodeIdByContentKey(
          bundleGroupNode.id,
        );
  
        if (
          !this._graph.hasEdge(
            bundleNodeId,
            bundleGroupNodeId,
            bundleGraphEdgeTypes.bundle,
          )
        ) {
          continue;
        }
  
        let inboundDependencies = this._graph
          .getNodeIdsConnectedTo(bundleGroupNodeId)
          .map(id => nullthrows(this._graph.getNode(id)))
          .filter(node => node.type === 'dependency')
          .map(node => {
            invariant(node.type === 'dependency');
            return node.value;
          });
  
        // If every inbound dependency to this bundle group does not belong to this bundle,
        // or the dependency is internal to the bundle, then the connection between
        // this bundle and the group is safe to remove.
        if (
          inboundDependencies.every(
            dependency =>
              !this.bundleHasDependency(bundle, dependency) ||
              this._graph.hasEdge(
                bundleNodeId,
                this._graph.getNodeIdByContentKey(dependency.id),
                bundleGraphEdgeTypes.internal_async,
              ),
          )
        ) {
          this._graph.removeEdge(
            bundleNodeId,
            bundleGroupNodeId,
            bundleGraphEdgeTypes.bundle,
          );
        }
      }
    }
  
    createAssetReference(
      dependency: Dependency,
      asset: Asset,
      bundle: Bundle,
    ): void {
      let dependencyId = this._graph.getNodeIdByContentKey(dependency.id);
      let assetId = this._graph.getNodeIdByContentKey(asset.id);
      let bundleId = this._graph.getNodeIdByContentKey(bundle.id);
      this._graph.addEdge(dependencyId, assetId, bundleGraphEdgeTypes.references);
  
      this._graph.addEdge(
        dependencyId,
        bundleId,
        bundleGraphEdgeTypes.references,
      );
      if (this._graph.hasEdge(dependencyId, assetId)) {
        this._graph.removeEdge(dependencyId, assetId);
      }
    }
  
    createBundleReference(from: Bundle, to: Bundle): void {
      this._graph.addEdge(
        this._graph.getNodeIdByContentKey(from.id),
        this._graph.getNodeIdByContentKey(to.id),
        bundleGraphEdgeTypes.references,
      );
    }
  
    getBundlesWithAsset(asset: Asset): Array<Bundle> {
      return this._graph
        .getNodeIdsConnectedTo(
          this._graph.getNodeIdByContentKey(asset.id),
          bundleGraphEdgeTypes.contains,
        )
        .map(id => nullthrows(this._graph.getNode(id)))
        .filter(node => node.type === 'bundle')
        .map(node => {
          invariant(node.type === 'bundle');
          return node.value;
        });
    }
  
    getBundlesWithDependency(dependency: Dependency): Array<Bundle> {
      return this._graph
        .getNodeIdsConnectedTo(
          nullthrows(this._graph.getNodeIdByContentKey(dependency.id)),
          bundleGraphEdgeTypes.contains,
        )
        .map(id => nullthrows(this._graph.getNode(id)))
        .filter(node => node.type === 'bundle')
        .map(node => {
          invariant(node.type === 'bundle');
          return node.value;
        });
    }
  
    getDependencyAssets(dependency: Dependency): Array<Asset> {
      return this._graph
        .getNodeIdsConnectedFrom(this._graph.getNodeIdByContentKey(dependency.id))
        .map(id => nullthrows(this._graph.getNode(id)))
        .filter(node => node.type === 'asset')
        .map(node => {
          invariant(node.type === 'asset');
          return node.value;
        });
    }
  
    getResolvedAsset(dep: Dependency, bundle: ?Bundle): ?Asset {
      let assets = this.getDependencyAssets(dep);
      let firstAsset = assets[0];
      let resolved =
        // If no bundle is specified, use the first concrete asset.
        bundle == null
          ? firstAsset
          : // Otherwise, find the first asset that belongs to this bundle.
            assets.find(asset => this.bundleHasAsset(bundle, asset)) ||
            firstAsset;
  
      // If a resolution still hasn't been found, return the first referenced asset.
      if (resolved == null) {
        this._graph.traverse(
          (nodeId, _, traversal) => {
            let node = nullthrows(this._graph.getNode(nodeId));
            if (node.type === 'asset') {
              resolved = node.value;
              traversal.stop();
            } else if (node.id !== dep.id) {
              traversal.skipChildren();
            }
          },
          this._graph.getNodeIdByContentKey(dep.id),
          bundleGraphEdgeTypes.references,
        );
      }
  
      return resolved;
    }
  
    getDependencies(asset: Asset): Array<Dependency> {
      let nodeId = this._graph.getNodeIdByContentKey(asset.id);
      return this._graph.getNodeIdsConnectedFrom(nodeId).map(id => {
        let node = nullthrows(this._graph.getNode(id));
        invariant(node.type === 'dependency');
        return node.value;
      });
    }
  
    traverseAssets<TContext>(
      bundle: Bundle,
      visit: GraphVisitor<Asset, TContext>,
    ): ?TContext {
      return this.traverseBundle(
        bundle,
        mapVisitor(node => (node.type === 'asset' ? node.value : null), visit),
      );
    }
  
    isAssetReferenced(bundle: Bundle, asset: Asset): boolean {
      let assetNodeId = nullthrows(this._graph.getNodeIdByContentKey(asset.id));
  
      if (
        this._graph
          .getNodeIdsConnectedTo(assetNodeId, bundleGraphEdgeTypes.references)
          .map(id => this._graph.getNode(id))
          .some(
            node =>
              node?.type === 'dependency' &&
              node.value.priority === Priority.lazy &&
              node.value.specifierType !== SpecifierType.url,
          )
      ) {
        // If this asset is referenced by any async dependency, it's referenced.
        return true;
      }
  
      let dependencies = this._graph
        .getNodeIdsConnectedTo(assetNodeId)
        .map(id => nullthrows(this._graph.getNode(id)))
        .filter(node => node.type === 'dependency')
        .map(node => {
          invariant(node.type === 'dependency');
          return node.value;
        });
  
      const bundleHasReference = (bundle: Bundle) => {
        return (
          !this.bundleHasAsset(bundle, asset) &&
          dependencies.some(dependency =>
            this.bundleHasDependency(bundle, dependency),
          )
        );
      };
  
      let visitedBundles: Set<Bundle> = new Set();
      let siblingBundles = new Set(
        this.getBundleGroupsContainingBundle(bundle).flatMap(bundleGroup =>
          this.getBundlesInBundleGroup(bundleGroup, {includeInline: true}),
        ),
      );
  
      // Check if any of this bundle's descendants, referencers, bundles referenced
      // by referencers, or descendants of its referencers use the asset without
      // an explicit reference edge. This can happen if e.g. the asset has been
      // deduplicated.
      return [...siblingBundles].some(referencer => {
        let isReferenced = false;
        this.traverseBundles((descendant, _, actions) => {
          if (descendant.id === bundle.id) {
            return;
          }
  
          if (visitedBundles.has(descendant)) {
            actions.skipChildren();
            return;
          }
  
          visitedBundles.add(descendant);
  
          if (
            descendant.type !== bundle.type ||
            descendant.env.context !== bundle.env.context
          ) {
            actions.skipChildren();
            return;
          }
  
          if (bundleHasReference(descendant)) {
            isReferenced = true;
            actions.stop();
            return;
          }
        }, referencer);
  
        return isReferenced;
      });
    }
  
    hasParentBundleOfType(bundle: Bundle, type: string): boolean {
      let parents = this.getParentBundles(bundle);
      return parents.length > 0 && parents.every(parent => parent.type === type);
    }
  
    getParentBundles(bundle: Bundle): Array<Bundle> {
      let parentBundles: Set<Bundle> = new Set();
      for (let bundleGroup of this.getBundleGroupsContainingBundle(bundle)) {
        for (let parentBundle of this.getParentBundlesOfBundleGroup(
          bundleGroup,
        )) {
          parentBundles.add(parentBundle);
        }
      }
  
      return [...parentBundles];
    }
  
    isAssetReachableFromBundle(asset: Asset, bundle: Bundle): boolean {
      // If a bundle's environment is isolated, it can't access assets present
      // in any ancestor bundles. Don't consider any assets reachable.
      if (
        ISOLATED_ENVS.has(bundle.env.context) ||
        !bundle.isSplittable ||
        bundle.bundleBehavior === BundleBehavior.isolated ||
        bundle.bundleBehavior === BundleBehavior.inline
      ) {
        return false;
      }
  
      // For an asset to be reachable from a bundle, it must either exist in a sibling bundle,
      // or in an ancestor bundle group reachable from all parent bundles.
      let bundleGroups = this.getBundleGroupsContainingBundle(bundle);
      return bundleGroups.every(bundleGroup => {
        // If the asset is in any sibling bundles of the original bundle, it is reachable.
        let bundles = this.getBundlesInBundleGroup(bundleGroup);
        if (
          bundles.some(
            b =>
              b.id !== bundle.id &&
              b.bundleBehavior !== BundleBehavior.isolated &&
              b.bundleBehavior !== BundleBehavior.inline &&
              this.bundleHasAsset(b, asset),
          )
        ) {
          return true;
        }
  
        // Get a list of parent bundle nodes pointing to the bundle group
        let parentBundleNodes = this._graph.getNodeIdsConnectedTo(
          this._graph.getNodeIdByContentKey(getBundleGroupId(bundleGroup)),
          bundleGraphEdgeTypes.bundle,
        );
  
        // Check that every parent bundle has a bundle group in its ancestry that contains the asset.
        return parentBundleNodes.every(bundleNodeId => {
          let bundleNode = nullthrows(this._graph.getNode(bundleNodeId));
          if (
            bundleNode.type !== 'bundle' ||
            bundleNode.value.bundleBehavior === BundleBehavior.isolated ||
            bundleNode.value.bundleBehavior === BundleBehavior.inline
          ) {
            return false;
          }
  
          let isReachable = true;
          this._graph.traverseAncestors(
            bundleNodeId,
            (nodeId, ctx, actions) => {
              let node = nullthrows(this._graph.getNode(nodeId));
              // If we've reached the root or a context change without
              // finding this asset in the ancestry, it is not reachable.
              if (
                node.type === 'root' ||
                (node.type === 'bundle' &&
                  (node.value.id === bundle.id ||
                    node.value.env.context !== bundle.env.context))
              ) {
                isReachable = false;
                actions.stop();
                return;
              }
  
              if (node.type === 'bundle_group') {
                let childBundles = this.getBundlesInBundleGroup(node.value);
                if (
                  childBundles.some(
                    b =>
                      b.id !== bundle.id &&
                      b.bundleBehavior !== BundleBehavior.isolated &&
                      b.bundleBehavior !== BundleBehavior.inline &&
                      this.bundleHasAsset(b, asset),
                  )
                ) {
                  actions.skipChildren();
                  return;
                }
              }
            },
            [bundleGraphEdgeTypes.references, bundleGraphEdgeTypes.bundle],
          );
  
          return isReachable;
        });
      });
    }
  
    traverseBundle<TContext>(
      bundle: Bundle,
      visit: GraphVisitor<AssetNode | DependencyNode, TContext>,
    ): ?TContext {
      let entries = true;
      let bundleNodeId = this._graph.getNodeIdByContentKey(bundle.id);
  
      // A modified DFS traversal which traverses entry assets in the same order
      // as their ids appear in `bundle.entryAssetIds`.
      return this._graph.dfs({
        visit: mapVisitor((nodeId, actions) => {
          let node = nullthrows(this._graph.getNode(nodeId));
  
          if (nodeId === bundleNodeId) {
            return;
          }
  
          if (node.type === 'dependency' || node.type === 'asset') {
            if (
              this._graph.hasEdge(
                bundleNodeId,
                nodeId,
                bundleGraphEdgeTypes.contains,
              )
            ) {
              return node;
            }
          }
  
          actions.skipChildren();
        }, visit),
        startNodeId: bundleNodeId,
        getChildren: nodeId => {
          let children = this._graph
            .getNodeIdsConnectedFrom(nodeId)
            .map(id => [id, nullthrows(this._graph.getNode(id))]);
  
          let sorted =
            entries && bundle.entryAssetIds.length > 0
              ? children.sort(([, a], [, b]) => {
                  let aIndex = bundle.entryAssetIds.indexOf(a.id);
                  let bIndex = bundle.entryAssetIds.indexOf(b.id);
  
                  if (aIndex === bIndex) {
                    // If both don't exist in the entry asset list, or
                    // otherwise have the same index.
                    return 0;
                  } else if (aIndex === -1) {
                    return 1;
                  } else if (bIndex === -1) {
                    return -1;
                  }
  
                  return aIndex - bIndex;
                })
              : children;
  
          entries = false;
          return sorted.map(([id]) => id);
        },
      });
    }
  
    traverse<TContext>(
      visit: GraphVisitor<AssetNode | DependencyNode, TContext>,
    ): ?TContext {
      return this._graph.filteredTraverse(
        nodeId => {
          let node = nullthrows(this._graph.getNode(nodeId));
          if (node.type === 'asset' || node.type === 'dependency') {
            return node;
          }
        },
        visit,
        undefined, // start with root
        // $FlowFixMe
        ALL_EDGE_TYPES,
      );
    }
  
    getChildBundles(bundle: Bundle): Array<Bundle> {
      let siblings = new Set(this.getReferencedBundles(bundle));
      let bundles = [];
      this.traverseBundles((b, _, actions) => {
        if (bundle.id === b.id) {
          return;
        }
  
        if (!siblings.has(b)) {
          bundles.push(b);
        }
  
        actions.skipChildren();
      }, bundle);
      return bundles;
    }
  
    traverseBundles<TContext>(
      visit: GraphVisitor<Bundle, TContext>,
      startBundle: ?Bundle,
    ): ?TContext {
      return this._graph.filteredTraverse(
        nodeId => {
          let node = nullthrows(this._graph.getNode(nodeId));
          return node.type === 'bundle' ? node.value : null;
        },
        visit,
        startBundle ? this._graph.getNodeIdByContentKey(startBundle.id) : null,
        [bundleGraphEdgeTypes.bundle, bundleGraphEdgeTypes.references],
      );
    }
  
    getBundles(opts?: {|includeInline: boolean|}): Array<Bundle> {
      let bundles = [];
      this.traverseBundles(bundle => {
        if (
          opts?.includeInline ||
          bundle.bundleBehavior !== BundleBehavior.inline
        ) {
          bundles.push(bundle);
        }
      });
  
      return bundles;
    }
  
    getTotalSize(asset: Asset): number {
      let size = 0;
      this._graph.traverse((nodeId, _, actions) => {
        let node = nullthrows(this._graph.getNode(nodeId));
        if (node.type === 'bundle_group') {
          actions.skipChildren();
          return;
        }
  
        if (node.type === 'asset') {
          size += node.value.stats.size;
        }
      }, this._graph.getNodeIdByContentKey(asset.id));
      return size;
    }
  
    getReferencingBundles(bundle: Bundle): Array<Bundle> {
      let referencingBundles: Set<Bundle> = new Set();
  
      this._graph.traverseAncestors(
        this._graph.getNodeIdByContentKey(bundle.id),
        nodeId => {
          let node = nullthrows(this._graph.getNode(nodeId));
          if (node.type === 'bundle' && node.value.id !== bundle.id) {
            referencingBundles.add(node.value);
          }
        },
        bundleGraphEdgeTypes.references,
      );
  
      return [...referencingBundles];
    }
  
    getBundleGroupsContainingBundle(bundle: Bundle): Array<BundleGroup> {
      let bundleGroups: Set<BundleGroup> = new Set();
  
      for (let currentBundle of [bundle, ...this.getReferencingBundles(bundle)]) {
        for (let bundleGroup of this.getDirectParentBundleGroups(currentBundle)) {
          bundleGroups.add(bundleGroup);
        }
      }
  
      return [...bundleGroups];
    }
  
    getDirectParentBundleGroups(bundle: Bundle): Array<BundleGroup> {
      return this._graph
        .getNodeIdsConnectedTo(
          nullthrows(this._graph.getNodeIdByContentKey(bundle.id)),
          bundleGraphEdgeTypes.bundle,
        )
        .map(id => nullthrows(this._graph.getNode(id)))
        .filter(node => node.type === 'bundle_group')
        .map(node => {
          invariant(node.type === 'bundle_group');
          return node.value;
        });
    }
  
    getBundlesInBundleGroup(
      bundleGroup: BundleGroup,
      opts?: {|includeInline: boolean|},
    ): Array<Bundle> {
      let bundles: Set<Bundle> = new Set();
      for (let bundleNodeId of this._graph.getNodeIdsConnectedFrom(
        this._graph.getNodeIdByContentKey(getBundleGroupId(bundleGroup)),
        bundleGraphEdgeTypes.bundle,
      )) {
        let bundleNode = nullthrows(this._graph.getNode(bundleNodeId));
        invariant(bundleNode.type === 'bundle');
        let bundle = bundleNode.value;
        if (
          opts?.includeInline ||
          bundle.bundleBehavior !== BundleBehavior.inline
        ) {
          bundles.add(bundle);
        }
  
        for (let referencedBundle of this.getReferencedBundles(bundle, {
          includeInline: true,
        })) {
          bundles.add(referencedBundle);
        }
      }
  
      return [...bundles];
    }
  
    getReferencedBundles(
      bundle: Bundle,
      opts?: {|recursive?: boolean, includeInline?: boolean|},
    ): Array<Bundle> {
      let recursive = opts?.recursive ?? true;
      let includeInline = opts?.includeInline ?? false;
      let referencedBundles = new Set();
      this._graph.dfs({
        visit: (nodeId, _, actions) => {
          let node = nullthrows(this._graph.getNode(nodeId));
          if (node.type !== 'bundle') {
            return;
          }
  
          if (node.value.id === bundle.id) {
            return;
          }
  
          if (
            includeInline ||
            node.value.bundleBehavior !== BundleBehavior.inline
          ) {
            referencedBundles.add(node.value);
          }
  
          if (!recursive) {
            actions.skipChildren();
          }
        },
        startNodeId: this._graph.getNodeIdByContentKey(bundle.id),
        getChildren: nodeId =>
          // Shared bundles seem to depend on being used in the opposite order
          // they were added.
          // TODO: Should this be the case?
          this._graph
            .getNodeIdsConnectedFrom(nodeId, bundleGraphEdgeTypes.references)
            .reverse(),
      });
  
      return [...referencedBundles];
    }
  
    getIncomingDependencies(asset: Asset): Array<Dependency> {
      if (!this._graph.hasContentKey(asset.id)) {
        return [];
      }
      // Dependencies can be a a parent node via an untyped edge (like in the AssetGraph but without AssetGroups)
      // or they can be parent nodes via a 'references' edge
      return this._graph
        .getNodeIdsConnectedTo(
          this._graph.getNodeIdByContentKey(asset.id),
          // $FlowFixMe
          ALL_EDGE_TYPES,
        )
        .map(id => nullthrows(this._graph.getNode(id)))
        .filter(n => n.type === 'dependency')
        .map(n => {
          invariant(n.type === 'dependency');
          return n.value;
        });
    }
  
    getAssetWithDependency(dep: Dependency): ?Asset {
      if (!this._graph.hasContentKey(dep.id)) {
        return null;
      }
  
      let res = this._graph.getNodeIdsConnectedTo(
        this._graph.getNodeIdByContentKey(dep.id),
      );
      invariant(
        res.length <= 1,
        'Expected a single asset to be connected to a dependency',
      );
      let resNode = this._graph.getNode(res[0]);
      if (resNode?.type === 'asset') {
        return resNode.value;
      }
    }
  
    bundleHasAsset(bundle: Bundle, asset: Asset): boolean {
      let bundleNodeId = this._graph.getNodeIdByContentKey(bundle.id);
      let assetNodeId = this._graph.getNodeIdByContentKey(asset.id);
      return this._graph.hasEdge(
        bundleNodeId,
        assetNodeId,
        bundleGraphEdgeTypes.contains,
      );
    }
  
    bundleHasDependency(bundle: Bundle, dependency: Dependency): boolean {
      let bundleNodeId = this._graph.getNodeIdByContentKey(bundle.id);
      let dependencyNodeId = this._graph.getNodeIdByContentKey(dependency.id);
      return this._graph.hasEdge(
        bundleNodeId,
        dependencyNodeId,
        bundleGraphEdgeTypes.contains,
      );
    }
  
    filteredTraverse<TValue, TContext>(
      bundleNodeId: NodeId,
      filter: (NodeId, TraversalActions) => ?TValue,
      visit: GraphVisitor<TValue, TContext>,
    ): ?TContext {
      return this._graph.filteredTraverse(filter, visit, bundleNodeId);
    }
  
    getSymbolResolution(
      asset: Asset,
      symbol: Symbol,
      boundary: ?Bundle,
    ): InternalSymbolResolution {
      let assetOutside = boundary && !this.bundleHasAsset(boundary, asset);
  
      let identifier = asset.symbols?.get(symbol)?.local;
      if (symbol === '*') {
        return {
          asset,
          exportSymbol: '*',
          symbol: identifier ?? null,
          loc: asset.symbols?.get(symbol)?.loc,
        };
      }
  
      let found = false;
      let skipped = false;
      let deps = this.getDependencies(asset).reverse();
      let potentialResults = [];
      for (let dep of deps) {
        let depSymbols = dep.symbols;
        if (!depSymbols) {
          found = true;
          continue;
        }
        // If this is a re-export, find the original module.
        let symbolLookup = new Map(
          [...depSymbols].map(([key, val]) => [val.local, key]),
        );
        let depSymbol = symbolLookup.get(identifier);
        if (depSymbol != null) {
          let resolved = this.getResolvedAsset(dep);
          if (!resolved || resolved.id === asset.id) {
            // External module or self-reference
            return {
              asset,
              exportSymbol: symbol,
              symbol: identifier,
              loc: asset.symbols?.get(symbol)?.loc,
            };
          }
  
          if (assetOutside) {
            // We found the symbol, but `asset` is outside, return `asset` and the original symbol
            found = true;
            break;
          }
  
          if (this.isDependencySkipped(dep)) {
            // We found the symbol and `dep` was skipped
            skipped = true;
            break;
          }
  
          let {
            asset: resolvedAsset,
            symbol: resolvedSymbol,
            exportSymbol,
            loc,
          } = this.getSymbolResolution(resolved, depSymbol, boundary);
  
          if (!loc) {
            // Remember how we got there
            loc = asset.symbols?.get(symbol)?.loc;
          }
  
          return {
            asset: resolvedAsset,
            symbol: resolvedSymbol,
            exportSymbol,
            loc,
          };
        }
        // If this module exports wildcards, resolve the original module.
        // Default exports are excluded from wildcard exports.
        // Wildcard reexports are never listed in the reexporting asset's symbols.
        if (
          identifier == null &&
          depSymbols.get('*')?.local === '*' &&
          symbol !== 'default'
        ) {
          let resolved = this.getResolvedAsset(dep);
          if (!resolved) {
            continue;
          }
          let result = this.getSymbolResolution(resolved, symbol, boundary);
  
          // We found the symbol
          if (result.symbol != undefined) {
            if (assetOutside) {
              // ..., but `asset` is outside, return `asset` and the original symbol
              found = true;
              break;
            }
            if (this.isDependencySkipped(dep)) {
              // We found the symbol and `dep` was skipped
              skipped = true;
              break;
            }
  
            return {
              asset: result.asset,
              symbol: result.symbol,
              exportSymbol: result.exportSymbol,
              loc: resolved.symbols?.get(symbol)?.loc,
            };
          }
          if (result.symbol === null) {
            found = true;
            if (boundary && !this.bundleHasAsset(boundary, result.asset)) {
              // If the returned asset is outside (and it's the first asset that is outside), return it.
              if (!assetOutside) {
                return {
                  asset: result.asset,
                  symbol: result.symbol,
                  exportSymbol: result.exportSymbol,
                  loc: resolved.symbols?.get(symbol)?.loc,
                };
              } else {
                // Otherwise the original asset will be returned at the end.
                break;
              }
            } else {
              // We didn't find it in this dependency, but it might still be there: bailout.
              // Continue searching though, with the assumption that there are no conficting reexports
              // and there might be a another (re)export (where we might statically find the symbol).
              potentialResults.push({
                asset: result.asset,
                symbol: result.symbol,
                exportSymbol: result.exportSymbol,
                loc: resolved.symbols?.get(symbol)?.loc,
              });
            }
          }
        }
      }
      // We didn't find the exact symbol...
      if (potentialResults.length == 1) {
        // ..., but if it does exist, it has to be behind this one reexport.
        return potentialResults[0];
      } else {
        // ... and there is no single reexport, but `bailout` tells us if it might still be exported.
        return {
          asset,
          exportSymbol: symbol,
          symbol: skipped
            ? false
            : found
            ? null
            : identifier ?? (asset.symbols?.has('*') ? null : undefined),
          loc: asset.symbols?.get(symbol)?.loc,
        };
      }
    }
    getAssetById(contentKey: string): Asset {
      let node = this._graph.getNodeByContentKey(contentKey);
      if (node == null) {
        throw new Error('Node not found');
      } else if (node.type !== 'asset') {
        throw new Error('Node was not an asset');
      }
  
      return node.value;
    }
  
    getAssetPublicId(asset: Asset): string {
      let publicId = this._publicIdByAssetId.get(asset.id);
      if (publicId == null) {
        throw new Error("Asset or it's public id not found");
      }
  
      return publicId;
    }
  
    getExportedSymbols(
      asset: Asset,
      boundary: ?Bundle,
    ): Array<InternalExportSymbolResolution> {
      if (!asset.symbols) {
        return [];
      }
  
      let symbols = [];
  
      for (let symbol of asset.symbols.keys()) {
        symbols.push({
          ...this.getSymbolResolution(asset, symbol, boundary),
          exportAs: symbol,
        });
      }
  
      let deps = this.getDependencies(asset);
      for (let dep of deps) {
        let depSymbols = dep.symbols;
        if (!depSymbols) continue;
  
        if (depSymbols.get('*')?.local === '*') {
          let resolved = this.getResolvedAsset(dep);
          if (!resolved) continue;
          let exported = this.getExportedSymbols(resolved, boundary)
            .filter(s => s.exportSymbol !== 'default')
            .map(s => ({...s, exportAs: s.exportSymbol}));
          symbols.push(...exported);
        }
      }
  
      return symbols;
    }
  
    getContentHash(bundle: Bundle): string {
      let existingHash = this._bundleContentHashes.get(bundle.id);
      if (existingHash != null) {
        return existingHash;
      }
  
      let hash = new Hash();
      // TODO: sort??
      this.traverseAssets(bundle, asset => {
        {
          hash.writeString(
            [
              this.getAssetPublicId(asset),
              asset.outputHash,
              asset.filePath,
              asset.query,
              asset.type,
              asset.uniqueKey,
            ].join(':'),
          );
        }
      });
  
      let hashHex = hash.finish();
      this._bundleContentHashes.set(bundle.id, hashHex);
      return hashHex;
    }
  
    getInlineBundles(bundle: Bundle): Array<Bundle> {
      let bundles = [];
      let seen = new Set();
      let addReferencedBundles = bundle => {
        if (seen.has(bundle.id)) {
          return;
        }
  
        seen.add(bundle.id);
  
        let referencedBundles = this.getReferencedBundles(bundle, {
          includeInline: true,
        });
        for (let referenced of referencedBundles) {
          if (referenced.bundleBehavior === BundleBehavior.inline) {
            bundles.push(referenced);
            addReferencedBundles(referenced);
          }
        }
      };
  
      addReferencedBundles(bundle);
  
      this.traverseBundles((childBundle, _, traversal) => {
        if (childBundle.bundleBehavior === BundleBehavior.inline) {
          bundles.push(childBundle);
        } else if (childBundle.id !== bundle.id) {
          traversal.skipChildren();
        }
      }, bundle);
  
      return bundles;
    }
  
    getHash(bundle: Bundle): string {
      let hash = new Hash();
      hash.writeString(
        bundle.id + bundle.target.publicUrl + this.getContentHash(bundle),
      );
  
      let inlineBundles = this.getInlineBundles(bundle);
      for (let inlineBundle of inlineBundles) {
        hash.writeString(this.getContentHash(inlineBundle));
      }
  
      for (let referencedBundle of this.getReferencedBundles(bundle)) {
        hash.writeString(referencedBundle.id);
      }
  
      hash.writeString(JSON.stringify(objectSortedEntriesDeep(bundle.env)));
      return hash.finish();
    }
  
    getBundleGraphHash(): string {
      let hashes = '';
      for (let bundle of this.getBundles()) {
        hashes += this.getHash(bundle);
      }
  
      return hashString(hashes);
    }
  
    addBundleToBundleGroup(bundle: Bundle, bundleGroup: BundleGroup) {
      let bundleGroupNodeId = this._graph.getNodeIdByContentKey(
        getBundleGroupId(bundleGroup),
      );
      let bundleNodeId = this._graph.getNodeIdByContentKey(bundle.id);
      if (
        this._graph.hasEdge(
          bundleGroupNodeId,
          bundleNodeId,
          bundleGraphEdgeTypes.bundle,
        )
      ) {
        // Bundle group already has bundle
        return;
      }
  
      this._graph.addEdge(bundleGroupNodeId, bundleNodeId);
      this._graph.addEdge(
        bundleGroupNodeId,
        bundleNodeId,
        bundleGraphEdgeTypes.bundle,
      );
  
      for (let entryAssetId of bundle.entryAssetIds) {
        let entryAssetNodeId = this._graph.getNodeIdByContentKey(entryAssetId);
        if (this._graph.hasEdge(bundleGroupNodeId, entryAssetNodeId)) {
          this._graph.removeEdge(bundleGroupNodeId, entryAssetNodeId);
        }
      }
    }
  
    getUsedSymbolsAsset(asset: Asset): $ReadOnlySet<Symbol> {
      let node = this._graph.getNodeByContentKey(asset.id);
      invariant(node && node.type === 'asset');
      return makeReadOnlySet(node.usedSymbols);
    }
  
    getUsedSymbolsDependency(dep: Dependency): $ReadOnlySet<Symbol> {
      let node = this._graph.getNodeByContentKey(dep.id);
      invariant(node && node.type === 'dependency');
      return makeReadOnlySet(node.usedSymbolsUp);
    }
  
    merge(other: BundleGraph) {
      let otherGraphIdToThisNodeId = new Map<NodeId, NodeId>();
      for (let [otherNodeId, otherNode] of other._graph.nodes) {
        if (this._graph.hasContentKey(otherNode.id)) {
          let existingNodeId = this._graph.getNodeIdByContentKey(otherNode.id);
          otherGraphIdToThisNodeId.set(otherNodeId, existingNodeId);
  
          let existingNode = nullthrows(this._graph.getNode(existingNodeId));
          // Merge symbols, recompute dep.exluded based on that
          if (existingNode.type === 'asset') {
            invariant(otherNode.type === 'asset');
            existingNode.usedSymbols = new Set([
              ...existingNode.usedSymbols,
              ...otherNode.usedSymbols,
            ]);
          } else if (existingNode.type === 'dependency') {
            invariant(otherNode.type === 'dependency');
            existingNode.usedSymbolsDown = new Set([
              ...existingNode.usedSymbolsDown,
              ...otherNode.usedSymbolsDown,
            ]);
            existingNode.usedSymbolsUp = new Set([
              ...existingNode.usedSymbolsUp,
              ...otherNode.usedSymbolsUp,
            ]);
  
            existingNode.excluded =
              (existingNode.excluded || Boolean(existingNode.hasDeferred)) &&
              (otherNode.excluded || Boolean(otherNode.hasDeferred));
          }
        } else {
          let updateNodeId = this._graph.addNodeByContentKey(
            otherNode.id,
            otherNode,
          );
          otherGraphIdToThisNodeId.set(otherNodeId, updateNodeId);
        }
      }
  
      for (let edge of other._graph.getAllEdges()) {
        this._graph.addEdge(
          nullthrows(otherGraphIdToThisNodeId.get(edge.from)),
          nullthrows(otherGraphIdToThisNodeId.get(edge.to)),
          edge.type,
        );
      }
    }
  
    isEntryBundleGroup(bundleGroup: BundleGroup): boolean {
      return this._graph
        .getNodeIdsConnectedTo(
          nullthrows(
            this._graph.getNodeIdByContentKey(getBundleGroupId(bundleGroup)),
          ),
          bundleGraphEdgeTypes.bundle,
        )
        .map(id => nullthrows(this._graph.getNode(id)))
        .some(n => n.type === 'root');
    }
  
    getEntryRoot(projectRoot: FilePath, target: Target): FilePath {
      let cached = this._targetEntryRoots.get(target.distDir);
      if (cached != null) {
        return cached;
      }
  
      let entryBundleGroupIds = this._graph.getNodeIdsConnectedFrom(
        nullthrows(this._graph.rootNodeId),
        bundleGraphEdgeTypes.bundle,
      );
  
      let entries = [];
      for (let bundleGroupId of entryBundleGroupIds) {
        let bundleGroupNode = this._graph.getNode(bundleGroupId);
        invariant(bundleGroupNode?.type === 'bundle_group');
  
        if (bundleGroupNode.value.target.distDir === target.distDir) {
          let entryAssetNode = this._graph.getNodeByContentKey(
            bundleGroupNode.value.entryAssetId,
          );
          invariant(entryAssetNode?.type === 'asset');
          entries.push(
            fromProjectPath(projectRoot, entryAssetNode.value.filePath),
          );
        }
      }
  
      let root = getRootDir(entries);
      this._targetEntryRoots.set(target.distDir, root);
      return root;
    }
  }
  