flags are now constrained to unsigned - compat with py 3.15

[bckohan]

No description provided.

[Copilot]

🔵 Needs a closer look

It changes fundamental flag-field storage/constraint semantics across backends and migrations, so it warrants final human review despite the added test coverage.

Pull request overview

This PR updates django-enum’s flag-field storage model so that the sign bit of 16/32/64-bit integer columns is usable as a flag (two’s complement encoding in signed columns), primarily to remain compatible with Python 3.15’s behavior around negative flag values.

Changes:

• Flag fields now store full-width flags in signed integer columns via two’s complement, rejecting negative-valued flag enums and adjusting validators/constraints accordingly.
• Fixes/adjusts ORM bitwise behavior (notably has_all on MySQL/MariaDB) and documents the required Value(..., output_field=...) wrapping for F() expressions when the top bit is involved.
• Adds new/updated tests and legacy migration coverage to ensure data written by django-enum 2.x remains readable after upgrading.

File summaries

File	Description
src/django_enum/fields.py	Implements two’s complement storage for flag fields, adds db_bit_length, updates constraint generation and validation.
src/django_enum/fields.pyi	Updates stubs/docs to reflect signed-column storage and new db_bit_length API.
src/django_enum/query.py	Adjusts has_all SQL for MySQL/MariaDB by casting bitwise results back to signed for correct comparisons with sign-bit flags.
tests/test_sign_bit.py	Adds focused tests for top-bit conversions, storage, querying, and constraint behavior.
tests/test_legacy_migrations.py	Adds migration regression tests to ensure 2.x-written data round-trips correctly after 3.x migrations.
tests/settings.py	Enables the new legacy migrations test app.
tests/legacy_migrations/**	Adds v2 model/settings scaffolding, frozen legacy migration, and the current models/migration for upgrade testing.
tests/test_flags.py	Updates bitwise F() expression tests to wrap RHS values where necessary; adjusts expected counts and unsupported lookup coverage.
tests/test_field_types.py / tests/test_constraints.py / tests/test_field_types_ep.py / tests/test_flags_ep.py	Updates expectations for signed integer storage and renamed “top-bit” enums.
tests/djenum/models.py / tests/djenum/enums.py / tests/enum_prop/models.py / tests/enum_prop/enums.py	Replaces negative-valued flag enums with non-negative top-bit variants consistent with the new storage rules.
tests/*/migrations/*.py	Regenerates test migrations to reflect the new field types/constraints and enum changes.
doc/source/howto/flags.rst	Documents full-width flag behavior and the F()/Value() requirement, plus MySQL/MariaDB limitations.
doc/source/changelog.rst	Adds v3.0.0 changelog details for the flag-field behavior change and upgrade implications.
justfile	Adds scripts to regenerate test migrations and frozen legacy migrations deterministically.
.gitignore	Adds .claude to ignored files.

Review details

• Files reviewed: 32/36 changed files
• Comments generated: 0
• Review effort level: Lite

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

Files with missing lines	Coverage Δ
src/django_enum/fields.py	100.00% <100.00%> (ø)
src/django_enum/query.py	100.00% <100.00%> (ø)

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