Add static type check with mypy (#2195)

* add mypy config

* fix syntax error

* fix annotations in torchvision/utils.py

* add mypy type check to CircleCI

* add mypy cache to ignore files

* try fix CI

* ignore flake8 F821 since it interferes with mypy

* add mypy type check to config generator

* explicitly set config files

.circleci/config.yml

@@ -109,7 +109,19 @@ jobs:
       - run:
           command: |
             pip install --user --progress-bar off flake8 typing
-            flake8 .
+            flake8 --config=setup.cfg .
+
+  python_type_check:
+    docker:
+      - image: circleci/python:3.7
+    steps:
+      - checkout
+      - run:
+          command: |
+            pip install --user --progress-bar off numpy mypy
+            pip install --user --progress-bar off --pre torch -f https://download.pytorch.org/whl/nightly/cpu/torch_nightly.html
+            pip install --user --progress-bar off .
+            mypy --config-file mypy.ini
 
   clang_format:
     docker:
@@ -702,12 +714,14 @@ workflows:
           python_version: "3.6"
           cu_version: "cu101"
       - python_lint
+      - python_type_check
       - clang_format
 
   nightly:
     jobs:
       - circleci_consistency
       - python_lint
+      - python_type_check
       - clang_format
       - binary_linux_wheel:
           cu_version: cpu

.circleci/config.yml.in

@@ -109,7 +109,19 @@ jobs:
       - run:
           command: |
             pip install --user --progress-bar off flake8 typing
-            flake8 .
+            flake8 --config=setup.cfg .
+
+  python_type_check:
+    docker:
+      - image: circleci/python:3.7
+    steps:
+      - checkout
+      - run:
+          command: |
+            pip install --user --progress-bar off numpy mypy
+            pip install --user --progress-bar off --pre torch -f https://download.pytorch.org/whl/nightly/cpu/torch_nightly.html
+            pip install --user --progress-bar off .
+            mypy --config-file mypy.ini
 
   clang_format:
     docker:
@@ -398,6 +410,7 @@ workflows:
           python_version: "3.6"
           cu_version: "cu101"
       - python_lint
+      - python_type_check
       - clang_format
 
   nightly:
@@ -405,5 +418,6 @@ workflows:
     jobs:
       - circleci_consistency
       - python_lint
+      - python_type_check
       - clang_format
       {{ workflows(prefix="nightly_", filter_branch="nightly", upload=True) }}

.gitignore

@@ -20,3 +20,4 @@ htmlcov
 *.swp
 *.swo
 gen.yml
+.mypy_cache

mypy.ini

+[mypy]
+
+files = torchvision
+show_error_codes = True
+pretty = True
+
+[mypy-torchvision.datasets.*]
+
+ignore_errors = True
+
+[mypy-torchvision.io.*]
+
+ignore_errors = True
+
+[mypy-torchvision.models.*]
+
+ignore_errors = True
+
+[mypy-torchvision.ops.*]
+
+ignore_errors = True
+
+[mypy-torchvision.transforms.*]
+
+ignore_errors = True
+
+[mypy-PIL]
+
+ignore_missing_imports = True
+

setup.cfg

@@ -9,5 +9,5 @@ max-line-length = 120
 
 [flake8]
 max-line-length = 120
-ignore = F401,E402,F403,W503,W504
+ignore = F401,E402,F403,W503,W504,F821
 exclude = venv

torchvision/io/_video_opt.py

@@ -84,7 +84,8 @@ class VideoMetaData(object):
 
 
 def _validate_pts(pts_range):
-    # type: (List[int])
+    # type: (List[int]) -> None
+
     if pts_range[1] > 0:
         assert (
             pts_range[0] <= pts_range[1]

torchvision/utils.py

-from typing import Union, Optional, Sequence, Tuple, Text, BinaryIO
+from typing import Union, Optional, List, Tuple, Text, BinaryIO
 import io
 import pathlib
 import torch
@@ -7,7 +7,7 @@ irange = range
 
 
 def make_grid(
-    tensor: Union[torch.Tensor, Sequence[torch.Tensor]],
+    tensor: Union[torch.Tensor, List[torch.Tensor]],
     nrow: int = 8,
     padding: int = 2,
     normalize: bool = False,
@@ -91,15 +91,17 @@ def make_grid(
         for x in irange(xmaps):
             if k >= nmaps:
                 break
-            grid.narrow(1, y * height + padding, height - padding)\
-                .narrow(2, x * width + padding, width - padding)\
-                .copy_(tensor[k])
+            # Tensor.copy_() is a valid method but seems to be missing from the stubs
+            # https://pytorch.org/docs/stable/tensors.html#torch.Tensor.copy_
+            grid.narrow(1, y * height + padding, height - padding).narrow(  # type: ignore[attr-defined]
+                2, x * width + padding, width - padding
+            ).copy_(tensor[k])
             k = k + 1
     return grid
 
 
 def save_image(
-    tensor: Union[torch.Tensor, Sequence[torch.Tensor]],
+    tensor: Union[torch.Tensor, List[torch.Tensor]],
     fp: Union[Text, pathlib.Path, BinaryIO],
     nrow: int = 8,
     padding: int = 2,