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Allow type checkers to ignore specific error codes #2153

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f4a919a
Allow type: ignore error codes filtering
davidhalter Feb 25, 2026
6ce8087
Try to improve the wording for the spec
davidhalter Mar 2, 2026
5cbcac4
Rephrase a bit of the spec
davidhalter Mar 2, 2026
6856262
Merge remote-tracking branch 'origin/main' into zuban-ignore
davidhalter Apr 14, 2026
ffc8e7c
Avoid specifying how whitespace after # type: ignore works
davidhalter Apr 14, 2026
a0bc8ad
Update conformance/tests/directives_type_ignore.py
davidhalter Apr 15, 2026
614bf60
Update docs/spec/directives.rst
davidhalter Apr 15, 2026
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3 changes: 0 additions & 3 deletions conformance/results/mypy/directives_type_ignore.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -5,11 +5,8 @@ Does not honor "# type: ignore" comment if comment includes additional text.
output = """
directives_type_ignore.py:11: error: Invalid "type: ignore" comment [syntax]
directives_type_ignore.py:11: error: Incompatible types in assignment (expression has type "str", variable has type "int") [assignment]
directives_type_ignore.py:14: error: Incompatible types in assignment (expression has type "str", variable has type "int") [assignment]
directives_type_ignore.py:14: note: Error code "assignment" not covered by "type: ignore" comment
"""
conformance_automated = "Fail"
errors_diff = """
Line 11: Unexpected errors ['directives_type_ignore.py:11: error: Invalid "type: ignore" comment [syntax]', 'directives_type_ignore.py:11: error: Incompatible types in assignment (expression has type "str", variable has type "int") [assignment]']
Line 14: Unexpected errors ['directives_type_ignore.py:14: error: Incompatible types in assignment (expression has type "str", variable has type "int") [assignment]']
"""
2 changes: 1 addition & 1 deletion conformance/results/results.html
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Expand Up @@ -1191,7 +1191,7 @@ <h3>Python Type System Conformance Test Results</h3>
<tr><th class="column col1">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;directives_type_ignore</th>
<th class="column col2 partially-conformant"><div class="hover-text">Partial<span class="tooltip-text" id="bottom"><p>Does not honor "# type: ignore" comment if comment includes additional text.</p></span></div></th>
<th class="column col2 conformant">Pass</th>
<th class="column col2 partially-conformant"><div class="hover-text">Partial<span class="tooltip-text" id="bottom"><p>Does not honor "# type: ignore" comment if comment includes additional text.</p></span></div></th>
<th class="column col2 conformant">Pass</th>
<th class="column col2 conformant">Pass</th>
<th class="column col2 partially-conformant"><div class="hover-text">Partial<span class="tooltip-text" id="bottom"><p>Treats `# type: ignore[error-code]` as only ignoring errors that match the error code `error-code`.</p></span></div></th>
</tr>
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9 changes: 1 addition & 8 deletions conformance/results/zuban/directives_type_ignore.toml
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@@ -1,12 +1,5 @@
conformant = "Partial"
notes = """
Does not honor "# type: ignore" comment if comment includes additional text.
"""
conformance_automated = "Fail"
conformance_automated = "Pass"
errors_diff = """
Line 14: Unexpected errors ['directives_type_ignore.py:14: error: Incompatible types in assignment (expression has type "str", variable has type "int") [assignment]']
"""
output = """
directives_type_ignore.py:14: error: Incompatible types in assignment (expression has type "str", variable has type "int") [assignment]
directives_type_ignore.py:14: note: Error code "assignment" not covered by "type: ignore" comment
"""
6 changes: 4 additions & 2 deletions conformance/tests/directives_type_ignore.py
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Expand Up @@ -10,8 +10,10 @@
# The following type violation should be suppressed.
y: int = "" # type: ignore - additional stuff

# The following type violation should be suppressed.
z: int = "" # type: ignore[additional_stuff]
# The following type violation may be suppressed, depending whether the
# type checker uses the error code `assignment` for invalid assignments,
# and/or how it treats unknown error codes.
z: int = "" # type: ignore[assignment]
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@carljm carljm Apr 14, 2026

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Suggested change
z: int = "" # type: ignore[assignment]
z: int = "" # type: ignore[assignment] # E?

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@carljm carljm Apr 14, 2026

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tbh I think it would be more "fair" to not change this line to use the type code that matches mypy/zuban. There's no specified requirement that all type checkers must use the type code assignment for this situation. So I think all type checkers that do strict handling of ignores with error codes should equally rely on # E? on this line.

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@davidhalter davidhalter Apr 15, 2026

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This is definitely fair. I'm indifferent here and will wait if there are any other opinions here.


# > In some cases, linting tools or other comments may be needed on the same
# > line as a type comment. In these cases, the type comment should be before
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9 changes: 9 additions & 0 deletions docs/spec/directives.rst
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Expand Up @@ -73,6 +73,15 @@ other comments and linting markers:

# type: ignore # <comment or other marker>

The form ``# type: ignore[...]`` may be used to suppress only type errors with a
given error code, though support for this is optional and may vary by type checker:

- Given ``# type: ignore[my_code1]``, a type checker may ignore the error code
``my_code1`` and choose to treat this form as equivalent to ``# type: ignore``.
- Alternatively, given ``# type: ignore[my_code1]`` a type checker may suppress the
error only if the error cause matches the error code ``my_code1``.
- A bare ``# type: ignore`` must always suppress all type errors.

.. _`cast`:

``cast()``
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