Silence modules in site-packages and typeshed (#5303)

Fixes #5260

Author: emmatyping

mypy/build.py

@@ -40,7 +40,7 @@
 from mypy.checker import TypeChecker
 from mypy.indirection import TypeIndirectionVisitor
 from mypy.errors import Errors, CompileError, report_internal_error
-from mypy.util import DecodeError, decode_python_encoding
+from mypy.util import DecodeError, decode_python_encoding, is_sub_path
 from mypy.report import Reports
 from mypy import moduleinfo
 from mypy.fixup import fixup_module
@@ -2387,7 +2387,11 @@ def find_module_and_diagnose(manager: BuildManager,
                     skipping_module(manager, caller_line, caller_state,
                                     id, path)
             raise ModuleNotFound
-
+        if not manager.options.no_silence_site_packages:
+            for dir in manager.search_paths.package_path + manager.search_paths.typeshed_path:
+                if is_sub_path(path, dir):
+                    # Silence errors in site-package dirs and typeshed
+                    follow_imports = 'silent'
         return (path, follow_imports)
     else:
         # Could not find a module.  Typically the reason is a

mypy/main.py

@@ -385,6 +385,9 @@ def add_invertible_flag(flag: str,
         '--no-site-packages', action='store_true',
         dest='special-opts:no_executable',
         help="do not search for installed PEP 561 compliant packages")
+    imports_group.add_argument(
+        '--no-silence-site-packages', action='store_true',
+        help="Do not silence errors in PEP 561 compliant installed packages")
 
     platform_group = parser.add_argument_group(
         title='platform configuration',

mypy/options.py

@@ -65,6 +65,8 @@ def __init__(self) -> None:
         self.custom_typeshed_dir = None  # type: Optional[str]
         self.mypy_path = []  # type: List[str]
         self.report_dirs = {}  # type: Dict[str, str]
+        # Show errors in PEP 561 packages/site-packages modules
+        self.no_silence_site_packages = False
         self.ignore_missing_imports = False
         self.follow_imports = 'normal'  # normal|silent|skip|error
         # Whether to respect the follow_imports setting even for stub files.

mypy/util.py

@@ -1,9 +1,12 @@
 """Utility functions with no non-trivial dependencies."""
-
+import genericpath  # type: ignore  # no stub files yet
+import os
+import pathlib
 import re
 import subprocess
+import sys
 from xml.sax.saxutils import escape
-from typing import TypeVar, List, Tuple, Optional, Dict
+from typing import TypeVar, List, Tuple, Optional, Dict, Sequence
 
 
 T = TypeVar('T')
@@ -204,3 +207,8 @@ def replace_object_state(new: object, old: object) -> None:
                         setattr(new, attr, getattr(old, attr))
                     elif hasattr(new, attr):
                         delattr(new, attr)
+
+
+def is_sub_path(path1: str, path2: str) -> bool:
+    """Given two paths, return if path1 is a sub-path of path2."""
+    return pathlib.Path(path2) in pathlib.Path(path1).parents

test-data/packages/typedpkg/typedpkg/sample.py

@@ -4,4 +4,4 @@
 def ex(a):
     # type: (Iterable[str]) -> Tuple[str, ...]
     """Example typed package."""
-    return tuple(a)
+    return list(a)

test-data/unit/fine-grained-modules.test

@@ -751,15 +751,16 @@ main:1: note: (Perhaps setting MYPYPATH or using the "--ignore-missing-imports"
 main:2: error: Incompatible types in assignment (expression has type "int", variable has type "str")
 
 [case testAddFileWhichImportsLibModuleWithErrors]
+# flags: --no-silence-site-packages
 import a
 a.x = 0
 [file a.py.2]
 import broken
 x = broken.x
 z
 [out]
-main:1: error: Cannot find module named 'a'
-main:1: note: (Perhaps setting MYPYPATH or using the "--ignore-missing-imports" flag would help)
+main:2: error: Cannot find module named 'a'
+main:2: note: (Perhaps setting MYPYPATH or using the "--ignore-missing-imports" flag would help)
 ==
 a.py:3: error: Name 'z' is not defined
 <ROOT>/test-data/unit/lib-stub/broken.pyi:2: error: Name 'y' is not defined