Switch to ignore-without-code control via error-code enablement

In preference to adding another specific command line flag.

Author: PeterJCLaw

docs/source/config_file.rst

@@ -507,13 +507,6 @@ section of the command line docs.
 
     Warns about unneeded ``# type: ignore`` comments.
 
-.. confval:: warn_ignores_without_codes
-
-    :type: boolean
-    :default: False
-
-    Warn about '# type: ignore' comments which do not have error codes.
-
 .. confval:: warn_no_return
 
     :type: boolean

docs/source/error_code_list2.rst

@@ -255,3 +255,31 @@ no error in practice. In such case, it might be prudent to annotate ``items: Seq
 This is similar in concept to ensuring that an expression's type implements an expected interface (e.g. ``Sized``),
 except that attempting to invoke an undefined method (e.g. ``__len__``) results in an error,
 while attempting to evaluate an object in boolean context without a concrete implementation results in a truthy value.
+
+
+Check that ``# type: ignore`` include an error code
+---------------------------------------------------
+
+Warn when an ``# type: ignore`` comment does not specify any error codes.
+This clarifies the intent of the ignore as well as ensuring that only the
+expected errors are silenced.
+
+Example:
+
+.. code-block:: python
+
+    # mypy: enable-error-code ignore-without-code
+
+    class Foo:
+        def __init__(self, name: str) -> None:
+            self.name = name
+
+    f = Foo('foo')
+
+    # This line has a typo that mypy can't help with as both the expected 'assignment' and 'attr-defined' are silenced
+    # Error: "type: ignore" comment without error code (currently ignored: [attr-defined])
+    f.nme = 42  # type: ignore
+
+    # This line warns correctly about the typo in the attribute name
+    # Error: "Foo" has no attribute "nme"; maybe "name"?
+    f.nme = 42  # type: ignore[assignment]

mypy/build.py

@@ -2370,7 +2370,7 @@ def generate_unused_ignore_notes(self) -> None:
             self.manager.errors.generate_unused_ignore_errors(self.xpath)
 
     def generate_ignore_without_code_notes(self) -> None:
-        if self.options.warn_ignores_without_codes:
+        if self.manager.errors.is_error_code_enabled(codes.IGNORE_WITHOUT_CODE):
             self.manager.errors.generate_ignore_without_code_errors(
                 self.xpath,
                 self.options.warn_unused_ignores,

mypy/options.py

@@ -49,7 +49,6 @@ class BuildType:
     "strict_equality",
     "strict_optional",
     "strict_optional_whitelist",
-    "warn_ignores_without_codes",
     "warn_no_return",
     "warn_return_any",
     "warn_unreachable",
@@ -144,9 +143,6 @@ def __init__(self) -> None:
         # Warn about unused '# type: ignore' comments
         self.warn_unused_ignores = False
 
-        # Warn about '# type: ignore' comments which do not have error codes
-        self.warn_ignores_without_codes = False
-
         # Warn about unused '[mypy-<pattern>]'  or '[[tool.mypy.overrides]]' config sections
         self.warn_unused_configs = False
 

test-data/unit/check-errorcodes.test

@@ -136,20 +136,20 @@ x # type: ignore[name-defined, attr-defined] # E: Unused "type: ignore[attr-defi
 "x" # type: ignore[name-defined] # E: Unused "type: ignore" comment
 
 [case testErrorCodeMissingWhenRequired]
-# flags: --warn-ignores-without-codes
+# flags: --enable-error-code ignore-without-code
 "x" # type: ignore # E: "type: ignore" comment without error code  [ignore-without-code]
 y # type: ignore # E: "type: ignore" comment without error code (hint: add [name-defined])  [ignore-without-code]
 z # type: ignore[name-defined]
 "a" # type: ignore[ignore-without-code]
 
 [case testErrorCodeMissingDoesntTrampleUnusedIgnoresWarning]
-# flags: --warn-ignores-without-codes --warn-unused-ignores
+# flags: --enable-error-code ignore-without-code --warn-unused-ignores
 "x" # type: ignore # E: Unused "type: ignore" comment
 "y" # type: ignore[ignore-without-code] # E: Unused "type: ignore" comment
 z # type: ignore[ignore-without-code] # E: Unused "type: ignore" comment # E: Name "z" is not defined  [name-defined]
 
 [case testErrorCodeMissingWholeFileIgnores]
-# flags: --warn-ignores-without-codes
+# flags: --enable-error-code ignore-without-code
 # type: ignore  # whole file ignore
 x
 y # type: ignore  # ignore the lack of error code since we're ignore the whole file