text: /**
   * @fileoverview Main Linter Class
   * @author Gyandeep Singh
   */
  
  "use strict";
  
  //------------------------------------------------------------------------------
  // Requirements
  //------------------------------------------------------------------------------
  
  const eslintScope = require("eslint-scope"),
      evk = require("eslint-visitor-keys"),
      espree = require("espree"),
      lodash = require("lodash"),
      CodePathAnalyzer = require("./code-path-analysis/code-path-analyzer"),
      ConfigOps = require("./config/config-ops"),
      validator = require("./config/config-validator"),
      Environments = require("./config/environments"),
      applyDisableDirectives = require("./util/apply-disable-directives"),
      createEmitter = require("./util/safe-emitter"),
      NodeEventGenerator = require("./util/node-event-generator"),
      SourceCode = require("./util/source-code"),
      Traverser = require("./util/traverser"),
      createReportTranslator = require("./util/report-translator"),
      Rules = require("./rules"),
      timing = require("./util/timing"),
      ConfigCommentParser = require("./util/config-comment-parser"),
      astUtils = require("./util/ast-utils"),
      pkg = require("../package.json"),
      SourceCodeFixer = require("./util/source-code-fixer");
  
  const debug = require("debug")("eslint:linter");
  const MAX_AUTOFIX_PASSES = 10;
  const DEFAULT_PARSER_NAME = "espree";
  const commentParser = new ConfigCommentParser();
  
  //------------------------------------------------------------------------------
  // Typedefs
  //------------------------------------------------------------------------------
  
  /**
   * The result of a parsing operation from parseForESLint()
   * @typedef {Object} CustomParseResult
   * @property {ASTNode} ast The ESTree AST Program node.
   * @property {Object} services An object containing additional services related
   *      to the parser.
   * @property {ScopeManager|null} scopeManager The scope manager object of this AST.
   * @property {Object|null} visitorKeys The visitor keys to traverse this AST.
   */
  
  /**
   * @typedef {Object} DisableDirective
   * @property {("disable"|"enable"|"disable-line"|"disable-next-line")} type
   * @property {number} line
   * @property {number} column
   * @property {(string|null)} ruleId
   */
  
  //------------------------------------------------------------------------------
  // Helpers
  //------------------------------------------------------------------------------
  
  /**
   * Ensures that variables representing built-in properties of the Global Object,
   * and any globals declared by special block comments, are present in the global
   * scope.
   * @param {Scope} globalScope The global scope.
   * @param {Object} configGlobals The globals declared in configuration
   * @param {{exportedVariables: Object, enabledGlobals: Object}} commentDirectives Directives from comment configuration
   * @returns {void}
   */
  function addDeclaredGlobals(globalScope, configGlobals, commentDirectives) {
      const mergedGlobalsInfo = Object.assign(
          {},
          lodash.mapValues(configGlobals, value => ({ sourceComment: null, value: ConfigOps.normalizeConfigGlobal(value) })),
          lodash.mapValues(commentDirectives.enabledGlobals, ({ comment, value }) => ({ sourceComment: comment, value: ConfigOps.normalizeConfigGlobal(value) }))
      );
  
      Object.keys(mergedGlobalsInfo)
          .filter(name => mergedGlobalsInfo[name].value !== "off")
          .forEach(name => {
              let variable = globalScope.set.get(name);
  
              if (!variable) {
                  variable = new eslintScope.Variable(name, globalScope);
                  if (mergedGlobalsInfo[name].sourceComment === null) {
                      variable.eslintExplicitGlobal = false;
                  } else {
                      variable.eslintExplicitGlobal = true;
                      variable.eslintExplicitGlobalComment = mergedGlobalsInfo[name].sourceComment;
                  }
                  globalScope.variables.push(variable);
                  globalScope.set.set(name, variable);
              }
              variable.writeable = (mergedGlobalsInfo[name].value === "writeable");
          });
  
      // mark all exported variables as such
      Object.keys(commentDirectives.exportedVariables).forEach(name => {
          const variable = globalScope.set.get(name);
  
          if (variable) {
              variable.eslintUsed = true;
          }
      });
  
      /*
       * "through" contains all references which definitions cannot be found.
       * Since we augment the global scope using configuration, we need to update
       * references and remove the ones that were added by configuration.
       */
      globalScope.through = globalScope.through.filter(reference => {
          const name = reference.identifier.name;
          const variable = globalScope.set.get(name);
  
          if (variable) {
  
              /*
               * Links the variable and the reference.
               * And this reference is removed from `Scope#through`.
               */
              reference.resolved = variable;
              variable.references.push(reference);
  
              return false;
          }
  
          return true;
      });
  }
  
  /**
   * Creates a collection of disable directives from a comment
   * @param {("disable"|"enable"|"disable-line"|"disable-next-line")} type The type of directive comment
   * @param {{line: number, column: number}} loc The 0-based location of the comment token
   * @param {string} value The value after the directive in the comment
   * comment specified no specific rules, so it applies to all rules (e.g. `eslint-disable`)
   * @returns {DisableDirective[]} Directives from the comment
   */
  function createDisableDirectives(type, loc, value) {
      const ruleIds = Object.keys(commentParser.parseListConfig(value));
      const directiveRules = ruleIds.length ? ruleIds : [null];
  
      return directiveRules.map(ruleId => ({ type, line: loc.line, column: loc.column + 1, ruleId }));
  }
  
  /**
   * Parses comments in file to extract file-specific config of rules, globals
   * and environments and merges them with global config; also code blocks
   * where reporting is disabled or enabled and merges them with reporting config.
   * @param {string} filename The file being checked.
   * @param {ASTNode} ast The top node of the AST.
   * @param {function(string): {create: Function}} ruleMapper A map from rule IDs to defined rules
   * @returns {{configuredRules: Object, enabledGlobals: Object, exportedVariables: Object, problems: Problem[], disableDirectives: DisableDirective[]}}
   * A collection of the directive comments that were found, along with any problems that occurred when parsing
   */
  function getDirectiveComments(filename, ast, ruleMapper) {
      const configuredRules = {};
      const enabledGlobals = {};
      const exportedVariables = {};
      const problems = [];
      const disableDirectives = [];
  
      ast.comments.filter(token => token.type !== "Shebang").forEach(comment => {
          const trimmedCommentText = comment.value.trim();
          const match = /^(eslint(-\w+){0,3}|exported|globals?)(\s|$)/u.exec(trimmedCommentText);
  
          if (!match) {
              return;
          }
  
          const directiveValue = trimmedCommentText.slice(match.index + match[1].length);
  
          if (/^eslint-disable-(next-)?line$/u.test(match[1])) {
              if (comment.loc.start.line === comment.loc.end.line) {
                  const directiveType = match[1].slice("eslint-".length);
  
                  disableDirectives.push(...createDisableDirectives(directiveType, comment.loc.start, directiveValue));
              } else {
                  problems.push({
                      ruleId: null,
                      severity: 2,
                      message: `${match[1]} comment should not span multiple lines.`,
                      line: comment.loc.start.line,
                      column: comment.loc.start.column + 1,
                      endLine: comment.loc.end.line,
                      endColumn: comment.loc.end.column + 1,
                      nodeType: null
                  });
              }
          } else if (comment.type === "Block") {
              switch (match[1]) {
                  case "exported":
                      Object.assign(exportedVariables, commentParser.parseStringConfig(directiveValue, comment));
                      break;
  
                  case "globals":
                  case "global":
                      Object.assign(enabledGlobals, commentParser.parseStringConfig(directiveValue, comment));
                      break;
  
                  case "eslint-disable":
                      disableDirectives.push(...createDisableDirectives("disable", comment.loc.start, directiveValue));
                      break;
  
                  case "eslint-enable":
                      disableDirectives.push(...createDisableDirectives("enable", comment.loc.start, directiveValue));
                      break;
  
                  case "eslint": {
                      const parseResult = commentParser.parseJsonConfig(directiveValue, comment.loc);
  
                      if (parseResult.success) {
                          Object.keys(parseResult.config).forEach(name => {
                              const ruleValue = parseResult.config[name];
  
                              try {
                                  validator.validateRuleOptions(ruleMapper(name), name, ruleValue);
                              } catch (err) {
                                  problems.push({
                                      ruleId: name,
                                      severity: 2,
                                      message: err.message,
                                      line: comment.loc.start.line,
                                      column: comment.loc.start.column + 1,
                                      endLine: comment.loc.end.line,
                                      endColumn: comment.loc.end.column + 1,
                                      nodeType: null
                                  });
                              }
                              configuredRules[name] = ruleValue;
                          });
                      } else {
                          problems.push(parseResult.error);
                      }
  
                      break;
                  }
  
                  // no default
              }
          }
      });
  
      return {
          configuredRules,
          enabledGlobals,
          exportedVariables,
          problems,
          disableDirectives
      };
  }
  
  /**
   * Normalize ECMAScript version from the initial config
   * @param  {number} ecmaVersion ECMAScript version from the initial config
   * @param  {boolean} isModule Whether the source type is module or not
   * @returns {number} normalized ECMAScript version
   */
  function normalizeEcmaVersion(ecmaVersion, isModule) {
  
      // Need at least ES6 for modules
      if (isModule && (!ecmaVersion || ecmaVersion < 6)) {
          return 6;
      }
  
      /*
       * Calculate ECMAScript edition number from official year version starting with
       * ES2015, which corresponds with ES6 (or a difference of 2009).
       */
      if (ecmaVersion >= 2015) {
          return ecmaVersion - 2009;
      }
  
      return ecmaVersion;
  }
  
  const eslintEnvPattern = /\/\*\s*eslint-env\s(.+?)\*\//gu;
  
  /**
   * Checks whether or not there is a comment which has "eslint-env *" in a given text.
   * @param {string} text - A source code text to check.
   * @returns {Object|null} A result of parseListConfig() with "eslint-env *" comment.
   */
  function findEslintEnv(text) {
      let match, retv;
  
      eslintEnvPattern.lastIndex = 0;
  
      while ((match = eslintEnvPattern.exec(text))) {
          retv = Object.assign(retv || {}, commentParser.parseListConfig(match[1]));
      }
  
      return retv;
  }
  
  /**
   * Normalizes the possible options for `linter.verify` and `linter.verifyAndFix` to a
   * consistent shape.
   * @param {(string|{reportUnusedDisableDirectives: boolean, filename: string, allowInlineConfig: boolean})} providedOptions Options
   * @returns {{reportUnusedDisableDirectives: boolean, filename: string, allowInlineConfig: boolean}} Normalized options
   */
  function normalizeVerifyOptions(providedOptions) {
      const isObjectOptions = typeof providedOptions === "object";
      const providedFilename = isObjectOptions ? providedOptions.filename : providedOptions;
  
      return {
          filename: typeof providedFilename === "string" ? providedFilename : "<input>",
          allowInlineConfig: !isObjectOptions || providedOptions.allowInlineConfig !== false,
          reportUnusedDisableDirectives: isObjectOptions && !!providedOptions.reportUnusedDisableDirectives
      };
  }
  
  /**
   * Combines the provided parserOptions with the options from environments
   * @param {string} parserName The parser name which uses this options.
   * @param {Object} providedOptions The provided 'parserOptions' key in a config
   * @param {Environment[]} enabledEnvironments The environments enabled in configuration and with inline comments
   * @returns {Object} Resulting parser options after merge
   */
  function resolveParserOptions(parserName, providedOptions, enabledEnvironments) {
      const parserOptionsFromEnv = enabledEnvironments
          .filter(env => env.parserOptions)
          .reduce((parserOptions, env) => ConfigOps.merge(parserOptions, env.parserOptions), {});
  
      const mergedParserOptions = ConfigOps.merge(parserOptionsFromEnv, providedOptions || {});
  
      const isModule = mergedParserOptions.sourceType === "module";
  
      if (isModule) {
  
          // can't have global return inside of modules
          mergedParserOptions.ecmaFeatures = Object.assign({}, mergedParserOptions.ecmaFeatures, { globalReturn: false });
      }
  
      mergedParserOptions.ecmaVersion = normalizeEcmaVersion(mergedParserOptions.ecmaVersion, isModule);
  
      // TODO: For backward compatibility. Will remove on v6.0.0.
      if (
          parserName === DEFAULT_PARSER_NAME &&
          mergedParserOptions.ecmaFeatures &&
          mergedParserOptions.ecmaFeatures.experimentalObjectRestSpread &&
          (!mergedParserOptions.ecmaVersion || mergedParserOptions.ecmaVersion < 9)
      ) {
          mergedParserOptions.ecmaVersion = 9;
      }
  
      return mergedParserOptions;
  }
  
  /**
   * Combines the provided globals object with the globals from environments
   * @param {Object} providedGlobals The 'globals' key in a config
   * @param {Environments[]} enabledEnvironments The environments enabled in configuration and with inline comments
   * @returns {Object} The resolved globals object
   */
  function resolveGlobals(providedGlobals, enabledEnvironments) {
      return Object.assign(
          {},
          ...enabledEnvironments.filter(env => env.globals).map(env => env.globals),
          providedGlobals
      );
  }
  
  /**
   * Strips Unicode BOM from a given text.
   *
   * @param {string} text - A text to strip.
   * @returns {string} The stripped text.
   */
  function stripUnicodeBOM(text) {
  
      /*
       * Check Unicode BOM.
       * In JavaScript, string data is stored as UTF-16, so BOM is 0xFEFF.
       * http://www.ecma-international.org/ecma-262/6.0/#sec-unicode-format-control-characters
       */
      if (text.charCodeAt(0) === 0xFEFF) {
          return text.slice(1);
      }
      return text;
  }
  
  /**
   * Get the options for a rule (not including severity), if any
   * @param {Array|number} ruleConfig rule configuration
   * @returns {Array} of rule options, empty Array if none
   */
  function getRuleOptions(ruleConfig) {
      if (Array.isArray(ruleConfig)) {
          return ruleConfig.slice(1);
      }
      return [];
  
  }
  
  /**
   * Analyze scope of the given AST.
   * @param {ASTNode} ast The `Program` node to analyze.
   * @param {Object} parserOptions The parser options.
   * @param {Object} visitorKeys The visitor keys.
   * @returns {ScopeManager} The analysis result.
   */
  function analyzeScope(ast, parserOptions, visitorKeys) {
      const ecmaFeatures = parserOptions.ecmaFeatures || {};
      const ecmaVersion = parserOptions.ecmaVersion || 5;
  
      return eslintScope.analyze(ast, {
          ignoreEval: true,
          nodejsScope: ecmaFeatures.globalReturn,
          impliedStrict: ecmaFeatures.impliedStrict,
          ecmaVersion,
          sourceType: parserOptions.sourceType || "script",
          childVisitorKeys: visitorKeys || evk.KEYS,
          fallback: Traverser.getKeys
      });
  }
  
  /**
   * Parses text into an AST. Moved out here because the try-catch prevents
   * optimization of functions, so it's best to keep the try-catch as isolated
   * as possible
   * @param {string} text The text to parse.
   * @param {Object} providedParserOptions Options to pass to the parser
   * @param {string} parserName The name of the parser
   * @param {Map<string, Object>} parserMap A map from names to loaded parsers
   * @param {string} filePath The path to the file being parsed.
   * @returns {{success: false, error: Problem}|{success: true, sourceCode: SourceCode}}
   * An object containing the AST and parser services if parsing was successful, or the error if parsing failed
   * @private
   */
  function parse(text, providedParserOptions, parserName, parserMap, filePath) {
  
  
      const textToParse = stripUnicodeBOM(text).replace(astUtils.SHEBANG_MATCHER, (match, captured) => `//${captured}`);
      const parserOptions = Object.assign({}, providedParserOptions, {
          loc: true,
          range: true,
          raw: true,
          tokens: true,
          comment: true,
          eslintVisitorKeys: true,
          eslintScopeManager: true,
          filePath
      });
  
      let parser;
  
      try {
          parser = parserMap.get(parserName) || require(parserName);
      } catch (ex) {
          return {
              success: false,
              error: {
                  ruleId: null,
                  fatal: true,
                  severity: 2,
                  message: ex.message,
                  line: 0,
                  column: 0
              }
          };
      }
  
      /*
       * Check for parsing errors first. If there's a parsing error, nothing
       * else can happen. However, a parsing error does not throw an error
       * from this method - it's just considered a fatal error message, a
       * problem that ESLint identified just like any other.
       */
      try {
          const parseResult = (typeof parser.parseForESLint === "function")
              ? parser.parseForESLint(textToParse, parserOptions)
              : { ast: parser.parse(textToParse, parserOptions) };
          const ast = parseResult.ast;
          const parserServices = parseResult.services || {};
          const visitorKeys = parseResult.visitorKeys || evk.KEYS;
          const scopeManager = parseResult.scopeManager || analyzeScope(ast, parserOptions, visitorKeys);
  
          return {
              success: true,
  
              /*
               * Save all values that `parseForESLint()` returned.
               * If a `SourceCode` object is given as the first parameter instead of source code text,
               * linter skips the parsing process and reuses the source code object.
               * In that case, linter needs all the values that `parseForESLint()` returned.
               */
              sourceCode: new SourceCode({
                  text,
                  ast,
                  parserServices,
                  scopeManager,
                  visitorKeys
              })
          };
      } catch (ex) {
  
          // If the message includes a leading line number, strip it:
          const message = `Parsing error: ${ex.message.replace(/^line \d+:/iu, "").trim()}`;
  
          return {
              success: false,
              error: {
                  ruleId: null,
                  fatal: true,
                  severity: 2,
                  message,
                  line: ex.lineNumber,
                  column: ex.column
              }
          };
      }
  }
  
  /**
   * Gets the scope for the current node
   * @param {ScopeManager} scopeManager The scope manager for this AST
   * @param {ASTNode} currentNode The node to get the scope of
   * @returns {eslint-scope.Scope} The scope information for this node
   */
  function getScope(scopeManager, currentNode) {
  
      // On Program node, get the outermost scope to avoid return Node.js special function scope or ES modules scope.
      const inner = currentNode.type !== "Program";
  
      for (let node = currentNode; node; node = node.parent) {
          const scope = scopeManager.acquire(node, inner);
  
          if (scope) {
              if (scope.type === "function-expression-name") {
                  return scope.childScopes[0];
              }
              return scope;
          }
      }
  
      return scopeManager.scopes[0];
  }
  
  /**
   * Marks a variable as used in the current scope
   * @param {ScopeManager} scopeManager The scope manager for this AST. The scope may be mutated by this function.
   * @param {ASTNode} currentNode The node currently being traversed
   * @param {Object} parserOptions The options used to parse this text
   * @param {string} name The name of the variable that should be marked as used.
   * @returns {boolean} True if the variable was found and marked as used, false if not.
   */
  function markVariableAsUsed(scopeManager, currentNode, parserOptions, name) {
      const hasGlobalReturn = parserOptions.ecmaFeatures && parserOptions.ecmaFeatures.globalReturn;
      const specialScope = hasGlobalReturn || parserOptions.sourceType === "module";
      const currentScope = getScope(scopeManager, currentNode);
  
      // Special Node.js scope means we need to start one level deeper
      const initialScope = currentScope.type === "global" && specialScope ? currentScope.childScopes[0] : currentScope;
  
      for (let scope = initialScope; scope; scope = scope.upper) {
          const variable = scope.variables.find(scopeVar => scopeVar.name === name);
  
          if (variable) {
              variable.eslintUsed = true;
              return true;
          }
      }
  
      return false;
  }
  
  /**
   * Runs a rule, and gets its listeners
   * @param {Rule} rule A normalized rule with a `create` method
   * @param {Context} ruleContext The context that should be passed to the rule
   * @returns {Object} A map of selector listeners provided by the rule
   */
  function createRuleListeners(rule, ruleContext) {
      try {
          return rule.create(ruleContext);
      } catch (ex) {
          ex.message = `Error while loading rule '${ruleContext.id}': ${ex.message}`;
          throw ex;
      }
  }
  
  /**
   * Gets all the ancestors of a given node
   * @param {ASTNode} node The node
   * @returns {ASTNode[]} All the ancestor nodes in the AST, not including the provided node, starting
   * from the root node and going inwards to the parent node.
   */
  function getAncestors(node) {
      const ancestorsStartingAtParent = [];
  
      for (let ancestor = node.parent; ancestor; ancestor = ancestor.parent) {
          ancestorsStartingAtParent.push(ancestor);
      }
  
      return ancestorsStartingAtParent.reverse();
  }
  
  // methods that exist on SourceCode object
  const DEPRECATED_SOURCECODE_PASSTHROUGHS = {
      getSource: "getText",
      getSourceLines: "getLines",
      getAllComments: "getAllComments",
      getNodeByRangeIndex: "getNodeByRangeIndex",
      getComments: "getComments",
      getCommentsBefore: "getCommentsBefore",
      getCommentsAfter: "getCommentsAfter",
      getCommentsInside: "getCommentsInside",
      getJSDocComment: "getJSDocComment",
      getFirstToken: "getFirstToken",
      getFirstTokens: "getFirstTokens",
      getLastToken: "getLastToken",
      getLastTokens: "getLastTokens",
      getTokenAfter: "getTokenAfter",
      getTokenBefore: "getTokenBefore",
      getTokenByRangeStart: "getTokenByRangeStart",
      getTokens: "getTokens",
      getTokensAfter: "getTokensAfter",
      getTokensBefore: "getTokensBefore",
      getTokensBetween: "getTokensBetween"
  };
  
  const BASE_TRAVERSAL_CONTEXT = Object.freeze(
      Object.keys(DEPRECATED_SOURCECODE_PASSTHROUGHS).reduce(
          (contextInfo, methodName) =>
              Object.assign(contextInfo, {
                  [methodName](...args) {
                      return this.getSourceCode()[DEPRECATED_SOURCECODE_PASSTHROUGHS[methodName]](...args);
                  }
              }),
          {}
      )
  );
  
  /**
   * Runs the given rules on the given SourceCode object
   * @param {SourceCode} sourceCode A SourceCode object for the given text
   * @param {Object} configuredRules The rules configuration
   * @param {function(string): Rule} ruleMapper A mapper function from rule names to rules
   * @param {Object} parserOptions The options that were passed to the parser
   * @param {string} parserName The name of the parser in the config
   * @param {Object} settings The settings that were enabled in the config
   * @param {string} filename The reported filename of the code
   * @returns {Problem[]} An array of reported problems
   */
  function runRules(sourceCode, configuredRules, ruleMapper, parserOptions, parserName, settings, filename) {
      const emitter = createEmitter();
      const nodeQueue = [];
      let currentNode = sourceCode.ast;
  
      Traverser.traverse(sourceCode.ast, {
          enter(node, parent) {
              node.parent = parent;
              nodeQueue.push({ isEntering: true, node });
          },
          leave(node) {
              nodeQueue.push({ isEntering: false, node });
          },
          visitorKeys: sourceCode.visitorKeys
      });
  
      /*
       * Create a frozen object with the ruleContext properties and methods that are shared by all rules.
       * All rule contexts will inherit from this object. This avoids the performance penalty of copying all the
       * properties once for each rule.
       */
      const sharedTraversalContext = Object.freeze(
          Object.assign(
              Object.create(BASE_TRAVERSAL_CONTEXT),
              {
                  getAncestors: () => getAncestors(currentNode),
                  getDeclaredVariables: sourceCode.scopeManager.getDeclaredVariables.bind(sourceCode.scopeManager),
                  getFilename: () => filename,
                  getScope: () => getScope(sourceCode.scopeManager, currentNode),
                  getSourceCode: () => sourceCode,
                  markVariableAsUsed: name => markVariableAsUsed(sourceCode.scopeManager, currentNode, parserOptions, name),
                  parserOptions,
                  parserPath: parserName,
                  parserServices: sourceCode.parserServices,
                  settings
              }
          )
      );
  
  
      const lintingProblems = [];
  
      Object.keys(configuredRules).forEach(ruleId => {
          const severity = ConfigOps.getRuleSeverity(configuredRules[ruleId]);
  
          if (severity === 0) {
              return;
          }
  
          const rule = ruleMapper(ruleId);
          const messageIds = rule.meta && rule.meta.messages;
          let reportTranslator = null;
          const ruleContext = Object.freeze(
              Object.assign(
                  Object.create(sharedTraversalContext),
                  {
                      id: ruleId,
                      options: getRuleOptions(configuredRules[ruleId]),
                      report(...args) {
  
                          /*
                           * Create a report translator lazily.
                           * In a vast majority of cases, any given rule reports zero errors on a given
                           * piece of code. Creating a translator lazily avoids the performance cost of
                           * creating a new translator function for each rule that usually doesn't get
                           * called.
                           *
                           * Using lazy report translators improves end-to-end performance by about 3%
                           * with Node 8.4.0.
                           */
                          if (reportTranslator === null) {
                              reportTranslator = createReportTranslator({ ruleId, severity, sourceCode, messageIds });
                          }
                          const problem = reportTranslator(...args);
  
                          if (problem.fix && rule.meta && !rule.meta.fixable) {
                              throw new Error("Fixable rules should export a `meta.fixable` property.");
                          }
                          lintingProblems.push(problem);
                      }
                  }
              )
          );
  
          const ruleListeners = createRuleListeners(rule, ruleContext);
  
          // add all the selectors from the rule as listeners
          Object.keys(ruleListeners).forEach(selector => {
              emitter.on(
                  selector,
                  timing.enabled
                      ? timing.time(ruleId, ruleListeners[selector])
                      : ruleListeners[selector]
              );
          });
      });
  
      const eventGenerator = new CodePathAnalyzer(new NodeEventGenerator(emitter));
  
      nodeQueue.forEach(traversalInfo => {
          currentNode = traversalInfo.node;
  
          try {
              if (traversalInfo.isEntering) {
                  eventGenerator.enterNode(currentNode);
              } else {
                  eventGenerator.leaveNode(currentNode);
              }
          } catch (err) {
              err.currentNode = currentNode;
              throw err;
          }
      });
  
      return lintingProblems;
  }
  
  const lastSourceCodes = new WeakMap();
  const loadedParserMaps = new WeakMap();
  const ruleMaps = new WeakMap();
  
  //------------------------------------------------------------------------------
  // Public Interface
  //------------------------------------------------------------------------------
  
  /**
   * Object that is responsible for verifying JavaScript text
   * @name eslint
   */
  module.exports = class Linter {
  
      constructor() {
          lastSourceCodes.set(this, null);
          loadedParserMaps.set(this, new Map());
          ruleMaps.set(this, new Rules());
          this.version = pkg.version;
          this.environments = new Environments();
  
          this.defineParser("espree", espree);
      }
  
      /**
       * Getter for package version.
       * @static
       * @returns {string} The version from package.json.
       */
      static get version() {
          return pkg.version;
      }
  
      /**
       * Configuration object for the `verify` API. A JS representation of the eslintrc files.
       * @typedef {Object} ESLintConfig
       * @property {Object} rules The rule configuration to verify against.
       * @property {string} [parser] Parser to use when generatig the AST.
       * @property {Object} [parserOptions] Options for the parsed used.
       * @property {Object} [settings] Global settings passed to each rule.
       * @property {Object} [env] The environment to verify in.
       * @property {Object} [globals] Available globals to the code.
       */
  
      /**
       * Same as linter.verify, except without support for processors.
       * @param {string|SourceCode} textOrSourceCode The text to parse or a SourceCode object.
       * @param {ESLintConfig} providedConfig An ESLintConfig instance to configure everything.
       * @param {(string|Object)} [filenameOrOptions] The optional filename of the file being checked.
       *      If this is not set, the filename will default to '<input>' in the rule context. If
       *      an object, then it has "filename", "saveState", and "allowInlineConfig" properties.
       * @param {boolean} [filenameOrOptions.allowInlineConfig=true] Allow/disallow inline comments' ability to change config once it is set. Defaults to true if not supplied.
       *      Useful if you want to validate JS without comments overriding rules.
       * @param {boolean} [filenameOrOptions.reportUnusedDisableDirectives=false] Adds reported errors for unused
       *      eslint-disable directives
       * @returns {Object[]} The results as an array of messages or an empty array if no messages.
       */
      _verifyWithoutProcessors(textOrSourceCode, providedConfig, filenameOrOptions) {
          const config = providedConfig || {};
          const options = normalizeVerifyOptions(filenameOrOptions);
          let text;
  
          // evaluate arguments
          if (typeof textOrSourceCode === "string") {
              lastSourceCodes.set(this, null);
              text = textOrSourceCode;
          } else {
              lastSourceCodes.set(this, textOrSourceCode);
              text = textOrSourceCode.text;
          }
  
          // search and apply "eslint-env *".
          const envInFile = findEslintEnv(text);
          const resolvedEnvConfig = Object.assign({ builtin: true }, config.env, envInFile);
          const enabledEnvs = Object.keys(resolvedEnvConfig)
              .filter(envName => resolvedEnvConfig[envName])
              .map(envName => this.environments.get(envName))
              .filter(env => env);
  
          const parserName = config.parser || DEFAULT_PARSER_NAME;
          const parserOptions = resolveParserOptions(parserName, config.parserOptions || {}, enabledEnvs);
          const configuredGlobals = resolveGlobals(config.globals || {}, enabledEnvs);
          const settings = config.settings || {};
  
          if (!lastSourceCodes.get(this)) {
              const parseResult = parse(
                  text,
                  parserOptions,
                  parserName,
                  loadedParserMaps.get(this),
                  options.filename
              );
  
              if (!parseResult.success) {
                  return [parseResult.error];
              }
  
              lastSourceCodes.set(this, parseResult.sourceCode);
          } else {
  
              /*
               * If the given source code object as the first argument does not have scopeManager, analyze the scope.
               * This is for backward compatibility (SourceCode is frozen so it cannot rebind).
               */
              const lastSourceCode = lastSourceCodes.get(this);
  
              if (!lastSourceCode.scopeManager) {
                  lastSourceCodes.set(this, new SourceCode({
                      text: lastSourceCode.text,
                      ast: lastSourceCode.ast,
                      parserServices: lastSourceCode.parserServices,
                      visitorKeys: lastSourceCode.visitorKeys,
                      scopeManager: analyzeScope(lastSourceCode.ast, parserOptions)
                  }));
              }
          }
  
          const sourceCode = lastSourceCodes.get(this);
          const commentDirectives = options.allowInlineConfig
              ? getDirectiveComments(options.filename, sourceCode.ast, ruleId => ruleMaps.get(this).get(ruleId))
              : { configuredRules: {}, enabledGlobals: {}, exportedVariables: {}, problems: [], disableDirectives: [] };
  
          // augment global scope with declared global variables
          addDeclaredGlobals(
              sourceCode.scopeManager.scopes[0],
              configuredGlobals,
              { exportedVariables: commentDirectives.exportedVariables, enabledGlobals: commentDirectives.enabledGlobals }
          );
  
          const configuredRules = Object.assign({}, config.rules, commentDirectives.configuredRules);
  
          let lintingProblems;
  
          try {
              lintingProblems = runRules(
                  sourceCode,
                  configuredRules,
                  ruleId => ruleMaps.get(this).get(ruleId),
                  parserOptions,
                  parserName,
                  settings,
                  options.filename
              );
          } catch (err) {
              err.message += `\nOccurred while linting ${options.filename}`;
              debug("An error occurred while traversing");
              debug("Filename:", options.filename);
              if (err.currentNode) {
                  const { line } = err.currentNode.loc.start;
  
                  debug("Line:", line);
                  err.message += `:${line}`;
              }
              debug("Parser Options:", parserOptions);
              debug("Parser Path:", parserName);
              debug("Settings:", settings);
              throw err;
          }
  
          return applyDisableDirectives({
              directives: commentDirectives.disableDirectives,
              problems: lintingProblems
                  .concat(commentDirectives.problems)
                  .sort((problemA, problemB) => problemA.line - problemB.line || problemA.column - problemB.column),
              reportUnusedDisableDirectives: options.reportUnusedDisableDirectives
          });
      }
  
      /**
       * Verifies the text against the rules specified by the second argument.
       * @param {string|SourceCode} textOrSourceCode The text to parse or a SourceCode object.
       * @param {ESLintConfig} config An ESLintConfig instance to configure everything.
       * @param {(string|Object)} [filenameOrOptions] The optional filename of the file being checked.
       *      If this is not set, the filename will default to '<input>' in the rule context. If
       *      an object, then it has "filename", "saveState", and "allowInlineConfig" properties.
       * @param {boolean} [filenameOrOptions.allowInlineConfig] Allow/disallow inline comments' ability to change config once it is set. Defaults to true if not supplied.
       *      Useful if you want to validate JS without comments overriding rules.
       * @param {function(string): string[]} [filenameOrOptions.preprocess] preprocessor for source text. If provided,
       *      this should accept a string of source text, and return an array of code blocks to lint.
       * @param {function(Array<Object[]>): Object[]} [filenameOrOptions.postprocess] postprocessor for report messages. If provided,
       *      this should accept an array of the message lists for each code block returned from the preprocessor,
       *      apply a mapping to the messages as appropriate, and return a one-dimensional array of messages
       * @returns {Object[]} The results as an array of messages or an empty array if no messages.
       */
      verify(textOrSourceCode, config, filenameOrOptions) {
          const preprocess = filenameOrOptions && filenameOrOptions.preprocess || (rawText => [rawText]);
          const postprocess = filenameOrOptions && filenameOrOptions.postprocess || lodash.flatten;
  
          return postprocess(
              preprocess(textOrSourceCode).map(
                  textBlock => this._verifyWithoutProcessors(textBlock, config, filenameOrOptions)
              )
          );
      }
  
      /**
       * Gets the SourceCode object representing the parsed source.
       * @returns {SourceCode} The SourceCode object.
       */
      getSourceCode() {
          return lastSourceCodes.get(this);
      }
  
      /**
       * Defines a new linting rule.
       * @param {string} ruleId A unique rule identifier
       * @param {Function} ruleModule Function from context to object mapping AST node types to event handlers
       * @returns {void}
       */
      defineRule(ruleId, ruleModule) {
          ruleMaps.get(this).define(ruleId, ruleModule);
      }
  
      /**
       * Defines many new linting rules.
       * @param {Object} rulesToDefine map from unique rule identifier to rule
       * @returns {void}
       */
      defineRules(rulesToDefine) {
          Object.getOwnPropertyNames(rulesToDefine).forEach(ruleId => {
              this.defineRule(ruleId, rulesToDefine[ruleId]);
          });
      }
  
      /**
       * Gets an object with all loaded rules.
       * @returns {Map} All loaded rules
       */
      getRules() {
          return ruleMaps.get(this).getAllLoadedRules();
      }
  
      /**
       * Define a new parser module
       * @param {any} parserId Name of the parser
       * @param {any} parserModule The parser object
       * @returns {void}
       */
      defineParser(parserId, parserModule) {
          loadedParserMaps.get(this).set(parserId, parserModule);
      }
  
      /**
       * Performs multiple autofix passes over the text until as many fixes as possible
       * have been applied.
       * @param {string} text The source text to apply fixes to.
       * @param {Object} config The ESLint config object to use.
       * @param {Object} options The ESLint options object to use.
       * @param {string} options.filename The filename from which the text was read.
       * @param {boolean} options.allowInlineConfig Flag indicating if inline comments
       *      should be allowed.
       * @param {boolean|Function} options.fix Determines whether fixes should be applied
       * @param {Function} options.preprocess preprocessor for source text. If provided, this should
       *      accept a string of source text, and return an array of code blocks to lint.
       * @param {Function} options.postprocess postprocessor for report messages. If provided,
       *      this should accept an array of the message lists for each code block returned from the preprocessor,
       *      apply a mapping to the messages as appropriate, and return a one-dimensional array of messages
       * @returns {Object} The result of the fix operation as returned from the
       *      SourceCodeFixer.
       */
      verifyAndFix(text, config, options) {
          let messages = [],
              fixedResult,
              fixed = false,
              passNumber = 0,
              currentText = text;
          const debugTextDescription = options && options.filename || `${text.slice(0, 10)}...`;
          const shouldFix = options && typeof options.fix !== "undefined" ? options.fix : true;
  
          /**
           * This loop continues until one of the following is true:
           *
           * 1. No more fixes have been applied.
           * 2. Ten passes have been made.
           *
           * That means anytime a fix is successfully applied, there will be another pass.
           * Essentially, guaranteeing a minimum of two passes.
           */
          do {
              passNumber++;
  
              debug(`Linting code for ${debugTextDescription} (pass ${passNumber})`);
              messages = this.verify(currentText, config, options);
  
              debug(`Generating fixed text for ${debugTextDescription} (pass ${passNumber})`);
              fixedResult = SourceCodeFixer.applyFixes(currentText, messages, shouldFix);
  
              /*
               * stop if there are any syntax errors.
               * 'fixedResult.output' is a empty string.
               */
              if (messages.length === 1 && messages[0].fatal) {
                  break;
              }
  
              // keep track if any fixes were ever applied - important for return value
              fixed = fixed || fixedResult.fixed;
  
              // update to use the fixed output instead of the original text
              currentText = fixedResult.output;
  
          } while (
              fixedResult.fixed &&
              passNumber < MAX_AUTOFIX_PASSES
          );
  
          /*
           * If the last result had fixes, we need to lint again to be sure we have
           * the most up-to-date information.
           */
          if (fixedResult.fixed) {
              fixedResult.messages = this.verify(currentText, config, options);
          }
  
          // ensure the last result properly reflects if fixes were done
          fixedResult.fixed = fixed;
          fixedResult.output = currentText;
  
          return fixedResult;
      }
  };
  