[Enhance] Support for installing minimal runtime dependencies

.circleci/test.yml

@@ -54,6 +54,33 @@ jobs:
           name: Run unit tests
           command: pytest tests/test_config tests/test_registry tests/test_fileio tests/test_logging tests/test_utils --ignore=tests/test_utils/test_dl_utils
 
+  build_lite:
+    parameters:
+      # The python version must match available image tags in
+      # https://circleci.com/developer/images/image/cimg/python
+      python:
+        type: string
+        default: "3.7.4"
+    docker:
+      - image: cimg/python:<< parameters.python >>
+    resource_class: large
+    steps:
+      - checkout
+      - run:
+          name: Upgrade pip
+          command: |
+            pip install pip --upgrade
+            pip --version
+      - run:
+          name: Build MMEngine from source
+          command: MMENGINE_LITE=1 pip install -e . -v
+      - run:
+          name: Install unit tests dependencies
+          command: pip install -r requirements/tests.txt
+      - run:
+          name: Run unit tests
+          command: pytest tests/test_config tests/test_registry tests/test_logging tests/test_utils --ignore=tests/test_utils/test_dl_utils
+
   build_cpu:
     parameters:
       # The python version must match available image tags in
@@ -217,6 +244,10 @@ workflows:
             branches:
               ignore:
                 - main
+      - build_lite:
+          name: build lite
+          requires:
+            - lint
       - build_without_torch:
           name: build without torch
           requires:

docs/en/get_started/installation.md

@@ -26,6 +26,15 @@
 
 ## Install MMEngine
 
+:::{note}
+If you only want to use the fileio, registry, and config modules in MMEngine, you can set the `MMENGINE_LITE` environment variable, which will only install the few third-party library dependencies that are necessary (e.g., it will not install opencv, matplotlib):
+
+```bash
+MMENGINE_LITE=1 pip install mmengine
+```
+
+:::
+
 ### Install with mim
 
 [mim](https://github.com/open-mmlab/mim) is a package management tool for OpenMMLab projects, which can be used to install the OpenMMLab project easily.

docs/zh_cn/get_started/installation.md

@@ -26,6 +26,15 @@
 
 ## 安装 MMEngine
 
+:::{note}
+如果你只想使用 MMEngine 中的 fileio、registry 和 config 模块，你可以设置 `MMENGINE_LITE` 环境变量，它只会安装必须的几个第三方库依赖（例如不会安装 opencv、matplotlib）：
+
+```bash
+MMENGINE_LITE=1 pip install mmengine
+```
+
+:::
+
 ### 使用 mim 安装
 
 [mim](https://github.com/open-mmlab/mim) 是 OpenMMLab 项目的包管理工具，使用它可以很方便地安装 OpenMMLab 项目。

requirements/runtime_lite.txt

@@ -0,0 +1,7 @@
+addict
+numpy
+pyyaml
+regex;sys_platform=='win32'
+rich
+termcolor
+yapf

setup.py

@@ -1,3 +1,4 @@
+import os
 import re
 from setuptools import find_packages, setup  # type: ignore
 
@@ -106,20 +107,23 @@ def gen_packages_items():
     return packages
 
 
-install_requires = parse_requirements()
-try:
-    # OpenCV installed via conda.
-    import cv2  # NOQA: F401
-    major, minor, *rest = cv2.__version__.split('.')
-    if int(major) < 3:
-        raise RuntimeError(
-            f'OpenCV >=3 is required but {cv2.__version__} is installed')
-except ImportError:
-    # If first not installed install second package
-    CHOOSE_INSTALL_REQUIRES = [('opencv-python-headless>=3',
-                                'opencv-python>=3')]
-    for main, secondary in CHOOSE_INSTALL_REQUIRES:
-        install_requires.append(choose_requirement(main, secondary))
+if int(os.getenv('MMENGINE_LITE', '0')) == 1:
+    install_requires = parse_requirements('requirements/runtime_lite.txt')
+else:
+    install_requires = parse_requirements()
+    try:
+        # OpenCV installed via conda.
+        import cv2  # NOQA: F401
+        major, minor, *rest = cv2.__version__.split('.')
+        if int(major) < 3:
+            raise RuntimeError(
+                f'OpenCV >=3 is required but {cv2.__version__} is installed')
+    except ImportError:
+        # If first not installed install second package
+        CHOOSE_INSTALL_REQUIRES = [('opencv-python-headless>=3',
+                                    'opencv-python>=3')]
+        for main, secondary in CHOOSE_INSTALL_REQUIRES:
+            install_requires.append(choose_requirement(main, secondary))
 
 setup(
     name='mmengine',