Implement disable ignores, a flag which disables all type ignores

This is available as a command-line flag and a global configuration option. This commit also includes documentation and tests for this feature. Fixes #13201

Author: wyattscarpenter

docs/source/command_line.rst

@@ -866,6 +866,12 @@ of the above sections.
         x = 'a string'
         x.trim()  # error: "str" has no attribute "trim"  [attr-defined]
 
+.. option:: --disable-ignores
+
+    This flag makes mypy act as though no ``# type: ignore`` comments are placed inline.
+    Effectively, it makes mypy "ignore ignores", therefore reporting all of the errors that would otherwise be ignored by those comments.
+    Beware: other configuration options and flags may still enable or disable various error codes.
+    The main use of this flag is to audit code that has ``# type: ignore`` comments in it (potentially masking problems in a subtle way).
 
 .. _configuring-error-messages:
 

docs/source/config_file.rst

@@ -800,6 +800,14 @@ section of the command line docs.
 
     Note: This option will override disabled error codes from the disable_error_code option.
 
+.. confval:: disable_ignores
+
+    :type: boolean
+    :default: false
+    :availability: global
+
+    Ignores ignores. See :option:`mypy --disable-ignores`.
+
 .. confval:: extra_checks
 
    :type: boolean

mypy/fastparse.py

@@ -896,12 +896,13 @@ def translate_module_id(self, id: str) -> str:
 
     def visit_Module(self, mod: ast3.Module) -> MypyFile:
         self.type_ignores = {}
-        for ti in mod.type_ignores:
-            parsed = parse_type_ignore_tag(ti.tag)
-            if parsed is not None:
-                self.type_ignores[ti.lineno] = parsed
-            else:
-                self.fail(message_registry.INVALID_TYPE_IGNORE, ti.lineno, -1, blocker=False)
+        if not self.options.disable_ignores:
+            for ti in mod.type_ignores:
+                parsed = parse_type_ignore_tag(ti.tag)
+                if parsed is not None:
+                    self.type_ignores[ti.lineno] = parsed
+                else:
+                    self.fail(message_registry.INVALID_TYPE_IGNORE, ti.lineno, -1, blocker=False)
 
         body = self.fix_function_overloads(self.translate_stmt_list(mod.body, ismodule=True))
 

mypy/main.py

@@ -956,6 +956,10 @@ def add_invertible_flag(
         help="Enable a specific error code",
     )
 
+    strictness_group.add_argument(
+        "--disable-ignores", action="store_true", help="Don't honor '# type: ignore' comments"
+    )
+
     error_group = parser.add_argument_group(
         title="Configuring error messages",
         description="Adjust the amount of detail shown in error messages.",

mypy/options.py

@@ -262,6 +262,9 @@ def __init__(self) -> None:
         self.enable_error_code: list[str] = []
         self.enabled_error_codes: set[ErrorCode] = set()
 
+        # Disable all type ignore comments
+        self.disable_ignores = False
+
         # Use script name instead of __main__
         self.scripts_are_modules = False
 

test-data/unit/check-flags.test

@@ -4,6 +4,25 @@ def f(x): pass
 [out]
 main:2: error: Function is missing a type annotation
 
+[case testDisableIgnores]
+# flags: --disable-ignores
+# type: ignore # a type ignore before everything usually ignores the entire file. But not now!
+a  # E: Name "a" is not defined
+a  #type: ignore  # E: Name "a" is not defined
+a  #type: ignore[golly]  # E: Name "a" is not defined
+a  #type: ignore[name-defined]  # E: Name "a" is not defined
+
+[case testDisableIgnoresConfig]
+# flags: --config-file tmp/mypy.ini
+# type: ignore # a type ignore before everything usually ignores the entire file. But not now!
+a  # E: Name "a" is not defined
+a  #type: ignore  # E: Name "a" is not defined
+a  #type: ignore[golly]  # E: Name "a" is not defined
+a  #type: ignore[name-defined]  # E: Name "a" is not defined
+[file mypy.ini]
+\[mypy]
+disable_ignores=True
+
 [case testUnannotatedArgument]
 # flags: --disallow-untyped-defs
 def f(x) -> int: pass