Fix a bug where inline configurations of error codes would lose their values if accompanied by another inline configuration. (#19075)

The following code produces a name-defined code error, despite our
instructions. How can it be?!

```py3
# mypy: disable-error-code=name-defined
# mypy: strict-equality
a
```

The answer is, there was a bug that caused all inline configurations,
even those that didn't specify any enable/disables, to overwrite the
lists of enable/disables. I have now fixed that. I've also added some
tests.

Closes #12342 — I discovered this problem while investigating the last
foible of issue #12342 (itself of tangential interest to something else
I was doing), which can now be closed.

---------

Co-authored-by: Stanislav Terliakov <[email protected]>

Author: wyattscarpenter

mypy/config_parser.py

@@ -650,17 +650,15 @@ def parse_mypy_comments(
     Returns a dictionary of options to be applied and a list of error messages
     generated.
     """
-
     errors: list[tuple[int, str]] = []
-    sections = {}
+    sections: dict[str, object] = {"enable_error_code": [], "disable_error_code": []}
 
     for lineno, line in args:
         # In order to easily match the behavior for bools, we abuse configparser.
         # Oddly, the only way to get the SectionProxy object with the getboolean
         # method is to create a config parser.
         parser = configparser.RawConfigParser()
         options, parse_errors = mypy_comments_to_config_map(line, template)
-
         if "python_version" in options:
             errors.append((lineno, "python_version not supported in inline configuration"))
             del options["python_version"]
@@ -690,9 +688,24 @@ def set_strict_flags() -> None:
                     '(see "mypy -h" for the list of flags enabled in strict mode)',
                 )
             )
-
+        # Because this is currently special-cased
+        # (the new_sections for an inline config *always* includes 'disable_error_code' and
+        # 'enable_error_code' fields, usually empty, which overwrite the old ones),
+        # we have to manipulate them specially.
+        # This could use a refactor, but so could the whole subsystem.
+        if (
+            "enable_error_code" in new_sections
+            and isinstance(neec := new_sections["enable_error_code"], list)
+            and isinstance(eec := sections.get("enable_error_code", []), list)
+        ):
+            new_sections["enable_error_code"] = sorted(set(neec + eec))
+        if (
+            "disable_error_code" in new_sections
+            and isinstance(ndec := new_sections["disable_error_code"], list)
+            and isinstance(dec := sections.get("disable_error_code", []), list)
+        ):
+            new_sections["disable_error_code"] = sorted(set(ndec + dec))
         sections.update(new_sections)
-
     return sections, errors
 
 

mypy/errorcodes.py

@@ -37,6 +37,10 @@ def __init__(
     def __str__(self) -> str:
         return f"<ErrorCode {self.code}>"
 
+    def __repr__(self) -> str:
+        """This doesn't fulfill the goals of repr but it's better than the default view."""
+        return f"<ErrorCode {self.category}: {self.code}>"
+
     def __eq__(self, other: object) -> bool:
         if not isinstance(other, ErrorCode):
             return False

mypy/options.py

@@ -507,7 +507,6 @@ def apply_changes(self, changes: dict[str, object]) -> Options:
             code = error_codes[code_str]
             new_options.enabled_error_codes.add(code)
             new_options.disabled_error_codes.discard(code)
-
         return new_options
 
     def compare_stable(self, other_snapshot: dict[str, object]) -> bool:

test-data/unit/check-inline-config.test

@@ -211,6 +211,99 @@ enable_error_code = ignore-without-code, truthy-bool
 \[mypy-tests.*]
 disable_error_code = ignore-without-code
 
+[case testInlineErrorCodesOverrideConfigSmall]
+# flags: --config-file tmp/mypy.ini
+import tests.baz
+[file tests/__init__.py]
+[file tests/baz.py]
+42 + "no"  # type: ignore
+
+[file mypy.ini]
+\[mypy]
+enable_error_code = ignore-without-code, truthy-bool
+
+\[mypy-tests.*]
+disable_error_code = ignore-without-code
+
+[case testInlineErrorCodesOverrideConfigSmall2]
+# flags: --config-file tmp/mypy.ini
+import tests.bar
+import tests.baz
+[file tests/__init__.py]
+[file tests/baz.py]
+42 + "no"  # type: ignore
+[file tests/bar.py]
+# mypy: enable-error-code="ignore-without-code"
+
+def foo() -> int: ...
+if foo: ...  # E: Function "foo" could always be true in boolean context
+42 + "no"  # type: ignore  # E: "type: ignore" comment without error code (consider "type: ignore[operator]" instead)
+
+[file mypy.ini]
+\[mypy]
+enable_error_code = ignore-without-code, truthy-bool
+
+\[mypy-tests.*]
+disable_error_code = ignore-without-code
+
+
+[case testInlineErrorCodesOverrideConfigSmallBackward]
+# flags: --config-file tmp/mypy.ini
+import tests.bar
+import tests.baz
+[file tests/__init__.py]
+[file tests/baz.py]
+42 + "no"  # type: ignore # E: "type: ignore" comment without error code (consider "type: ignore[operator]" instead)
+[file tests/bar.py]
+# mypy: disable-error-code="ignore-without-code"
+42 + "no"  # type: ignore
+
+[file mypy.ini]
+\[mypy]
+enable_error_code = ignore-without-code, truthy-bool
+
+\[mypy-tests.*]
+enable_error_code = ignore-without-code
+
+[case testInlineOverrideConfig]
+# flags: --config-file tmp/mypy.ini
+import foo
+import tests.bar
+import tests.baz
+[file foo.py]
+# mypy: disable-error-code="truthy-bool"
+class Foo:
+    pass
+
+foo = Foo()
+if foo: ...
+42 # type: ignore  # E: Unused "type: ignore" comment
+
+[file tests/__init__.py]
+[file tests/bar.py]
+# mypy: warn_unused_ignores
+
+def foo() -> int: ...
+if foo: ...  # E: Function "foo" could always be true in boolean context
+42 # type: ignore  # E: Unused "type: ignore" comment
+
+[file tests/baz.py]
+# mypy: disable-error-code="truthy-bool"
+class Foo:
+    pass
+
+foo = Foo()
+if foo: ...
+42 # type: ignore
+
+[file mypy.ini]
+\[mypy]
+warn_unused_ignores = True
+
+\[mypy-tests.*]
+warn_unused_ignores = False
+
+
 [case testIgnoreErrorsSimple]
 # mypy: ignore-errors=True
 
@@ -324,6 +417,61 @@ foo = Foo()
 if foo: ...
 42 + "no"  # type: ignore
 
-
 [case testInlinePythonVersion]
 # mypy: python-version=3.10  # E: python_version not supported in inline configuration
+
+[case testInlineErrorCodesArentRuinedByOthersBaseCase]
+# mypy: disable-error-code=name-defined
+a
+
+[case testInlineErrorCodesArentRuinedByOthersInvalid]
+# mypy: disable-error-code=name-defined
+# mypy: AMONGUS
+a
+[out]
+main:2: error: Unrecognized option: amongus = True
+
+[case testInlineErrorCodesArentRuinedByOthersInvalidBefore]
+# mypy: AMONGUS
+# mypy: disable-error-code=name-defined
+a
+[out]
+main:1: error: Unrecognized option: amongus = True
+
+[case testInlineErrorCodesArentRuinedByOthersSe]
+# mypy: disable-error-code=name-defined
+# mypy: strict-equality
+def is_magic(x: bytes) -> bool:
+    y
+    return x == 'magic' # E: Unsupported left operand type for == ("bytes")
+
+[case testInlineConfigErrorCodesOffAndOn]
+# mypy: disable-error-code=name-defined
+# mypy: enable-error-code=name-defined
+a # E: Name "a" is not defined
+
+[case testInlineConfigErrorCodesOnAndOff]
+# mypy: enable-error-code=name-defined
+# mypy: disable-error-code=name-defined
+a # E: Name "a" is not defined
+
+[case testConfigFileErrorCodesOnAndOff]
+# flags: --config-file tmp/mypy.ini
+import foo
+[file foo.py]
+42 + "no"  # type: ignore  # E: "type: ignore" comment without error code (consider "type: ignore[operator]" instead)
+[file mypy.ini]
+\[mypy]
+enable_error_code = ignore-without-code
+disable_error_code = ignore-without-code
+
+[case testInlineConfigBaseCaseWui]
+# mypy: warn_unused_ignores
+x = 1 # type: ignore # E: Unused "type: ignore" comment
+
+[case testInlineConfigIsntRuinedByOthersInvalidWui]
+# mypy: warn_unused_ignores
+# mypy: AMONGUS
+x = 1 # type: ignore # E: Unused "type: ignore" comment
+[out]
+main:2: error: Unrecognized option: amongus = True