python: fix BSUnit ctypes binding

[jeroendiederen]

Pass BSUnit as a ctypes union to bs_size_convert_to and add a conversion regression test. Also make the translation canary shell test POSIX-compatible.

Fix the Python ctypes binding for bs_size_convert_to().

BSUnit is a C union containing the binary and decimal unit enums, but
the Python binding previously passed the unit as a plain ctypes.c_int.
Define a matching ctypes.Union and use it for the function argument.

Also fix the conversion unit test to verify that 1 MiB converts to
1024 KiB, and make the translation canary shell test POSIX-compatible.

Tests:

• make check
• git diff --check

All tests pass.

Summary by CodeRabbit

• Bug Fixes

  • Improved conversion between binary and decimal size units.
  • Corrected conversion handling so values produce accurate results across unit types.

• Tests

  • Added verification that converting 1 MiB to KiB returns 1024.
  • Improved portability and reliability of distribution detection checks.

[coderabbitai]

📝 Walkthrough

Walkthrough

The Python binding now uses a public SizeUnit ctypes union for native conversions. Conversion tests verify 1 MiB to KiB. The canary script uses POSIX-compatible distro checks.

Changes

Unit conversion

Layer / File(s)	Summary
ctypes unit binding src/python/bytesize.py, tests/libbytesize_unittest.py	The binding defines SizeUnit, passes binary units through the union, updates the native signature, and verifies that 1 MiB converts to "1024" KiB.
Test script portability tests/canary_tests.sh.in	The distro detection command uses multiline formatting and quoted POSIX `

Estimated code review effort: 3 (Moderate) | ~20 minutes

Mergeability Score: ⚪ Minimal · up to 97faf

The change corrects Python unit conversion binding behavior and updates related tests and shell compatibility; no actionable merge-blocking risk remains after normal checks and review.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely identifies the main change: fixing the Python ctypes binding for the size unit union.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}

[coderabbitai]

🧹 Nitpick comments (2)

tests/libbytesize_unittest.py (1)

368-369: 🗄️ Data Integrity & Integration | 🔵 Trivial | ⚡ Quick win

Add coverage for decimal units.

This test covers only MiB to KiB. Add a 1 MB to KB assertion to verify the decimal-unit path through SizeUnit.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@tests/libbytesize_unittest.py` around lines 368 - 369, Add a decimal-unit
assertion alongside the existing SizeStruct.new_from_str test, converting “1 MB”
to KB and expecting “1000”. Keep the current binary-unit MiB-to-KiB assertion
unchanged to cover both SizeUnit paths.

src/python/bytesize.py (1)

84-88: 📐 Maintainability & Code Quality | 🔵 Trivial | ⚡ Quick win

Address the RUF012 warning on SizeUnit._fields_.

Ruff reports this list as a mutable class attribute. If Ruff is enforced, annotate _fields_ as a ClassVar or use an immutable sequence accepted by the supported ctypes versions. Keep any suppression scoped to this declaration.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@src/python/bytesize.py` around lines 84 - 88, Update the SizeUnit._fields_
declaration to address RUF012 by annotating it as a ClassVar or replacing the
list with an immutable sequence supported by the project’s ctypes versions. Keep
any lint suppression narrowly scoped to this declaration.

Source: Linters/SAST tools

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Nitpick comments:
In `@src/python/bytesize.py`:
- Around line 84-88: Update the SizeUnit._fields_ declaration to address RUF012
by annotating it as a ClassVar or replacing the list with an immutable sequence
supported by the project’s ctypes versions. Keep any lint suppression narrowly
scoped to this declaration.

In `@tests/libbytesize_unittest.py`:
- Around line 368-369: Add a decimal-unit assertion alongside the existing
SizeStruct.new_from_str test, converting “1 MB” to KB and expecting “1000”. Keep
the current binary-unit MiB-to-KiB assertion unchanged to cover both SizeUnit
paths.

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro Plus

Run ID: 9a7dcd7f-8547-4720-8cab-f3c355cd7a25

📥 Commits

Reviewing files that changed from the base of the PR and between 229561b and 97faf40.

📒 Files selected for processing (3)

• src/python/bytesize.py
• tests/canary_tests.sh.in
• tests/libbytesize_unittest.py

[vojtechtrefny]

Thank you, looks good to me in general, just few small changes.

[vojtechtrefny]

This works, but I think it would be better to set the correct member based on the unit. So dunit for MB/21 or larger and bunit else.

[vojtechtrefny]

Please also add a check with a decimal unit.