lazy.py

# SPDX-FileCopyrightText: Copyright (c) 2025 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
# SPDX-License-Identifier: Apache-2.0
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import ast
import builtins
import collections.abc as abc
import importlib
import inspect
import os
import uuid
from collections import OrderedDict
from contextlib import contextmanager
from dataclasses import is_dataclass
from typing import Any, Dict, List, Tuple, Union

import attrs
import yaml
from omegaconf import DictConfig, ListConfig, OmegaConf

from .file_io import PathManager
from .registry import _convert_target_to_string

__all__ = ["LazyCall", "LazyConfig"]


def sort_dict(d: Dict[str, Any]) -> OrderedDict[str, Any]:
    return OrderedDict(sorted(d.items(), key=lambda x: x[0]))


def dict_representer(dumper: yaml.Dumper, data: OrderedDict[str, Any]) -> yaml.nodes.MappingNode:
    return dumper.represent_mapping("tag:yaml.org,2002:map", data.items())


def sort_recursive(obj: Union[Dict[str, Any], List[Any], Any]) -> Union[OrderedDict[str, Any], List[Any], Any]:
    if isinstance(obj, dict):
        return sort_dict({k: sort_recursive(v) for k, v in obj.items()})
    elif isinstance(obj, list):
        return [sort_recursive(item) for item in obj]
    return obj


yaml.add_representer(OrderedDict, dict_representer)


def get_default_params(cls_or_func):
    if callable(cls_or_func):
        # inspect signature for function
        signature = inspect.signature(cls_or_func)
    else:
        # inspect signature for class
        signature = inspect.signature(cls_or_func.__init__)
    params = signature.parameters
    default_params = {
        name: param.default for name, param in params.items() if param.default is not inspect.Parameter.empty
    }
    return default_params


class LazyCall:
    """
    Wrap a callable so that when it's called, the call will not be executed,
    but returns a dict that describes the call.

    LazyCall object has to be called with only keyword arguments. Positional
    arguments are not yet supported.

    Examples:
    ::
        # prevent huggingface from checking detectron2: from detectron2.config import instantiate, LazyCall

        layer_cfg = LazyCall(nn.Conv2d)(in_channels=32, out_channels=32)
        layer_cfg.out_channels = 64   # can edit it afterwards
        layer = instantiate(layer_cfg)
    """

    def __init__(self, target):
        if not (callable(target) or isinstance(target, (str, abc.Mapping))):
            raise TypeError(f"target of LazyCall must be a callable or defines a callable! Got {target}")
        self._target = target

    def __call__(self, **kwargs):
        if is_dataclass(self._target) or attrs.has(self._target):
            # omegaconf object cannot hold dataclass type
            # https://github.com/omry/omegaconf/issues/784
            target = _convert_target_to_string(self._target)
        else:
            target = self._target
        kwargs["_target_"] = target

        _final_params = get_default_params(self._target)
        _final_params.update(kwargs)

        return DictConfig(content=_final_params, flags={"allow_objects": True})


def _visit_dict_config(cfg, func):
    """
    Apply func recursively to all DictConfig in cfg.
    """
    if isinstance(cfg, DictConfig):
        func(cfg)
        for v in cfg.values():
            _visit_dict_config(v, func)
    elif isinstance(cfg, ListConfig):
        for v in cfg:
            _visit_dict_config(v, func)


def _validate_py_syntax(filename):
    # see also https://github.com/open-mmlab/mmcv/blob/master/mmcv/utils/config.py
    with PathManager.open(filename, "r") as f:
        content = f.read()
    try:
        ast.parse(content)
    except SyntaxError as e:
        raise SyntaxError(f"Config file {filename} has syntax error!") from e


def _cast_to_config(obj):
    # if given a dict, return DictConfig instead
    if isinstance(obj, dict):
        return DictConfig(obj, flags={"allow_objects": True})
    return obj


_CFG_PACKAGE_NAME = "detectron2._cfg_loader"
"""
A namespace to put all imported config into.
"""


def _random_package_name(filename):
    # generate a random package name when loading config files
    return _CFG_PACKAGE_NAME + str(uuid.uuid4())[:4] + "." + os.path.basename(filename)


@contextmanager
def _patch_import():
    """
    Enhance relative import statements in config files, so that they:
    1. locate files purely based on relative location, regardless of packages.
       e.g. you can import file without having __init__
    2. do not cache modules globally; modifications of module states has no side effect
    3. support other storage system through PathManager, so config files can be in the cloud
    4. imported dict are turned into omegaconf.DictConfig automatically
    """
    old_import = builtins.__import__

    def find_relative_file(original_file, relative_import_path, level):
        # NOTE: "from . import x" is not handled. Because then it's unclear
        # if such import should produce `x` as a python module or DictConfig.
        # This can be discussed further if needed.
        relative_import_err = """
Relative import of directories is not allowed within config files.
Within a config file, relative import can only import other config files.
""".replace(
            "\n", " "
        )
        if not len(relative_import_path):
            raise ImportError(relative_import_err)

        cur_file = os.path.dirname(original_file)
        for _ in range(level - 1):
            cur_file = os.path.dirname(cur_file)
        cur_name = relative_import_path.lstrip(".")
        for part in cur_name.split("."):
            cur_file = os.path.join(cur_file, part)
        if not cur_file.endswith(".py"):
            cur_file += ".py"
        if not PathManager.isfile(cur_file):
            cur_file_no_suffix = cur_file[: -len(".py")]
            if PathManager.isdir(cur_file_no_suffix):
                raise ImportError(f"Cannot import from {cur_file_no_suffix}." + relative_import_err)
            else:
                raise ImportError(
                    f"Cannot import name {relative_import_path} from " f"{original_file}: {cur_file} does not exist."
                )
        return cur_file

    def new_import(name, globals=None, locals=None, fromlist=(), level=0):
        if (
            # Only deal with relative imports inside config files
            level != 0
            and globals is not None
            and (globals.get("__package__", "") or "").startswith(_CFG_PACKAGE_NAME)
        ):
            cur_file = find_relative_file(globals["__file__"], name, level)
            _validate_py_syntax(cur_file)
            spec = importlib.machinery.ModuleSpec(_random_package_name(cur_file), None, origin=cur_file)
            module = importlib.util.module_from_spec(spec)
            module.__file__ = cur_file
            with PathManager.open(cur_file) as f:
                content = f.read()
            exec(compile(content, cur_file, "exec"), module.__dict__)
            for name in fromlist:  # turn imported dict into DictConfig automatically
                val = _cast_to_config(module.__dict__[name])
                module.__dict__[name] = val
            return module
        return old_import(name, globals, locals, fromlist=fromlist, level=level)

    builtins.__import__ = new_import
    yield new_import
    builtins.__import__ = old_import


class LazyConfig:
    """
    Provide methods to save, load, and overrides an omegaconf config object
    which may contain definition of lazily-constructed objects.
    """

    @staticmethod
    def load(filename: str, keys: Union[None, str, Tuple[str, ...]] = None):
        """
        Load a config file.

        Args:
            filename: absolute path or relative path w.r.t. the current working directory
            keys: keys to load and return. If not given, return all keys
                (whose values are config objects) in a dict.
        """
        has_keys = keys is not None
        filename = filename.replace("/./", "/")  # redundant
        if os.path.splitext(filename)[1] not in [".py", ".yaml", ".yml"]:
            raise ValueError(f"Config file {filename} has to be a python or yaml file.")
        if filename.endswith(".py"):
            _validate_py_syntax(filename)

            with _patch_import():
                # Record the filename
                module_namespace = {
                    "__file__": filename,
                    "__package__": _random_package_name(filename),
                }
                with PathManager.open(filename) as f:
                    content = f.read()
                # Compile first with filename to:
                # 1. make filename appears in stacktrace
                # 2. make load_rel able to find its parent's (possibly remote) location
                exec(compile(content, filename, "exec"), module_namespace)

            ret = module_namespace
        else:
            with PathManager.open(filename) as f:
                obj = yaml.unsafe_load(f)
            ret = OmegaConf.create(obj, flags={"allow_objects": True})

        if has_keys:
            if isinstance(keys, str):
                return _cast_to_config(ret[keys])
            else:
                return tuple(_cast_to_config(ret[a]) for a in keys)
        else:
            if filename.endswith(".py"):
                # when not specified, only load those that are config objects
                ret = DictConfig(
                    {
                        name: _cast_to_config(value)
                        for name, value in ret.items()
                        if isinstance(value, (DictConfig, ListConfig, dict)) and not name.startswith("_")
                    },
                    flags={"allow_objects": True},
                )
            return ret