Sandbox::https://github.com/sqlalchemy/sqlalchemy/pull/13532

Faseeh06 · 2026-08-24T09:49:58Z

_produce_column_copies(), used when a Column or MappedColumn is inherited from a mixin/non-declarative base and copied onto the class being mapped, calls _collect_annotation() with expect_mapped hardcoded to True at both of its call sites. This bypasses self.allow_unmapped_annotations entirely, so a bare (non-Mapped[]) type-annotated attribute paired with such a column — inherited from a mixin — raises MappedAnnotationError even when __allow_unmapped__ = True is set on the mapped class or a superclass, despite the error's own text claiming that flag should suppress it:

class Base(DeclarativeBase):
    __allow_unmapped__ = True

class Mixin:
    id: int = Column(Integer, primary_key=True)

class MyModel(Mixin, Base):
    __tablename__ = "my_model"
    # currently raises MappedAnnotationError despite __allow_unmapped__

By contrast, the equivalent path for attributes declared directly on the mapped class passes expect_mapped=None, which correctly defers to the flag via the dynamic computation already present in _collect_annotation.

Changes

Pass not self.allow_unmapped_annotations instead of a hardcoded True at both _produce_column_copies() call sites, preserving the strict default while honoring the flag, matching the direct-attribute path's behavior.
Added a regression test (test_allow_unmapped_column_on_mixin) alongside the existing test_allow_unmapped_on_mixin/test_allow_unmapped_cols tests.
Added a changelog entry.

Test plan

Reproduced the exact repro from the issue against current main, confirmed fixed
Confirmed the strict default (no __allow_unmapped__) still correctly raises MappedAnnotationError for the same mixin shape — no over-broadening
New test fails on unmodified main and passes with the fix
pytest test/orm/declarative/ — 2852 passed
pytest test/orm/ (full ORM suite) — 10937 passed
flake8 / black --check clean on both changed files

_produce_column_copies(), used when a Column or MappedColumn is inherited from a mixin/non-declarative base and copied onto the mapped class, called _collect_annotation() with expect_mapped hardcoded to True at both of its call sites. This bypassed self.allow_unmapped_annotations entirely, so a bare (non-Mapped[]) annotation paired with such a column raised MappedAnnotationError even when __allow_unmapped__ = True was set - despite the error's own text claiming that flag should suppress it. By contrast, the equivalent path for attributes declared directly on the mapped class passes expect_mapped=None, correctly deferring to the flag via the dynamic computation in _collect_annotation. Pass "not self.allow_unmapped_annotations" instead of a hardcoded True at both call sites, so the strict default is preserved but the flag is now honored, matching the direct-attribute path.

sqla-tester · 2026-08-24T09:50:08Z

Hi, and thanks for the pull request!

This project accepts pull requests only for issues that a maintainer has already marked with the open for pull requests label. That way we can settle on an approach before anyone spends time writing code.

This pull request references issue #9369, which hasn't been marked open for pull requests, so the change isn't authorized yet and I'm closing it automatically. Once a maintainer adds the label to #9369, reopen this pull request and it will stay open. If #9369 needs more detail before that can happen, a complete runnable example is usually the missing piece, and adding one to the issue is the fastest way to get there.

This is automatic and procedural. It isn't a judgment on your change, and nothing you've written here is lost.

Thanks for your interest in the project!

Mukller · 2026-08-24T15:12:06Z

Traced this through both functions to be sure, and the two-line fix is semantically exact:

With expect_mapped=False (i.e. __allow_unmapped__ = True), a bare annotation takes the return annotated, None branch in _extract_mapped_subtype (orm/util.py) instead of raising — the column then copies over with its plain type, exactly what allow_unmapped seems to not be honored in all cases #9369 asks for.
A Mapped[...] annotation on a mixin-inherited Column/MappedColumn is unaffected: the raise-block only triggers when the annotation's __origin__ isn't _MappedAnnotationBase, so extraction proceeds identically under either expect_mapped value.
With the flag off, expect_mapped=True reproduces the old behavior bit-for-bit, so non-mixin / strict-mode paths see no change.

The regression test targets the right path (mixin + explicit Column + bare annotation goes through _produce_column_copies, unlike the adjacent non-Column test), and asserting on __table__.c.keys() verifies both attributes survived rather than just absence-of-exception.

Nothing else to flag — clean fix for a long-standing gap.

CaselIT · 2026-08-24T19:00:43Z

+                    name,
+                    annotation,
+                    originating_class,
+                    not self.allow_unmapped_annotations,


I think this and below could instead pass None.

@zzzeek thoughts?

in other places for such a case we pass none not False

he's correct. use None please, instead of True

also we need to document what "allow_unmapped" means, determine if False means anything and if not we need to change this parameter

what im getting at is this is a bigger change that warrants a lot of care and caution. it's not a one liner. especially in the tests. needs a lot more and they need to be integrated with what we have already.

@zzzeek Should I check it at broader level and then let you know ?

if you want, sure

zzzeek · 2026-08-24T19:25:37Z

+    def test_allow_unmapped_column_on_mixin(self, decl_base):
+        """test #9369"""
+
+        class Mixin:


this is not what the test case in the issue says....the test case has the __allow_unmapped__ on the Mixin.

in fact we should test it in all combinations: on just the mixin, on just the concrete class, on both. use testing.variations

zzzeek · 2026-08-24T19:26:02Z

+
+        class MyClass(Mixin, decl_base):
+            __tablename__ = "mytable"
+            __allow_unmapped__ = True


this file will also need to be copied using tools/sync_test_files.py

sqla-tester closed this Aug 24, 2026

CaselIT reopened this Aug 24, 2026

CaselIT reviewed Aug 24, 2026

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zzzeek requested changes Aug 24, 2026

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Fix __allow_unmapped__ not honored for Column/MappedColumn on mixins - #13532

Fix __allow_unmapped__ not honored for Column/MappedColumn on mixins#13532
Faseeh06 wants to merge 1 commit into
sqlalchemy:mainfrom
Faseeh06:fix/allow-unmapped-mixin-columns

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Faseeh06 commented Aug 24, 2026

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