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Allow creating PyCapsule objects#7595

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youknowone merged 1 commit into
RustPython:mainfrom
bschoenmaeckers:pycapsule
Apr 14, 2026
Merged

Allow creating PyCapsule objects#7595
youknowone merged 1 commit into
RustPython:mainfrom
bschoenmaeckers:pycapsule

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@bschoenmaeckers

@bschoenmaeckers bschoenmaeckers commented Apr 13, 2026 •
edited by coderabbitai Bot
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Allow creation of PyCapsule objects. The destructor is a C function for easy interop with other languages.

Summary by CodeRabbit

Release Notes

  • New Features
    • Capsule objects now support storing opaque pointers with optional destructor callbacks for proper resource cleanup
    • Added new APIs to create capsules and retrieve stored pointer data

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coderabbitai Bot commented Apr 13, 2026 •
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📝 Walkthrough

Walkthrough

Modified the PyCapsule struct to store an opaque pointer and optional C-level destructor callback instead of remaining empty. Added public constructor and accessor methods to PyCapsule, extended it with Destructor trait support, and introduced a helper method Context::new_capsule() for creating capsule instances.

Changes

Cohort / File(s) Summary
Capsule Implementation
crates/vm/src/builtins/capsule.rs		 Changed PyCapsule from a zero-sized struct to store AtomicPtr<c_void> and an optional unsafe extern "C" destructor. Added new() constructor, pointer() accessor, removed Clone/Copy derives, and implemented Destructor trait for cleanup on deletion.
Context Helper
crates/vm/src/vm/context.rs		 Added new_capsule() method to Context that constructs and binds a PyCapsule instance from a raw pointer and optional C destructor callback.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Poem

🐰 A capsule is born with a pointer so true,
A destructor assigned when its work is through,
From context we craft it, in memory it sleeps,
A guardian of pointers, the secrets it keeps! ✨

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name Status Explanation Resolution
Docstring Coverage ⚠️ Warning Docstring coverage is 22.22% which is insufficient. The required threshold is 80.00%. Write docstrings for the functions missing them to satisfy the coverage threshold.
✅ Passed checks (2 passed)
Check name Status Explanation
Description Check ✅ Passed Check skipped - CodeRabbit’s high-level summary is enabled.
Title check ✅ Passed The title 'Allow creating PyCapsule objects' directly and clearly summarizes the main change: adding the ability to create PyCapsule objects with new constructor methods and capsule support.

✏️ Tip: You can configure your own custom pre-merge checks in the settings.

✨ Finishing Touches
🧪 Generate unit tests (beta)
  • Create PR with unit tests

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coderabbitai[bot]
coderabbitai Bot reviewed Apr 13, 2026
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Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents 
Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@crates/vm/src/builtins/capsule.rs`:
- Around line 28-35: The constructor Capsule::new currently accepts a raw ptr
and stores it without validation; update it to reject NULL pointers by
validating ptr before constructing—either change the signature to return
Result<Self, ErrorType> (e.g., Result<Capsule, InvalidPointerError>) and return
an Err when ptr.is_null(), or perform a defensive check and panic with a clear
message; ensure the check happens before setting self.ptr and mention
PyCapsule_New and PyCapsule_IsValid semantics in the error or panic so callers
know NULL is not allowed, and keep the destructor handling unchanged.
🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

  • Push a commit to this branch (recommended)
  • Create a new PR with the fixes
ℹ️ Review info
⚙️ Run configuration

Configuration used: Path: .coderabbit.yml

Review profile: CHILL

Plan: Pro

Run ID: 89365b54-c937-4160-99bf-fe663f7677a7

📥 Commits

Reviewing files that changed from the base of the PR and between 7e637e8 and dcecdf9.

📒 Files selected for processing (2)
  • crates/vm/src/builtins/capsule.rs
  • crates/vm/src/vm/context.rs

ShaharNaveh
ShaharNaveh reviewed Apr 13, 2026
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@ShaharNaveh ShaharNaveh left a comment

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welcome to the project:)
can you please share some information about this change? what is it trying to achieve?

@bschoenmaeckers

bschoenmaeckers commented Apr 13, 2026

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welcome to the project:)
can you please share some information about this change? what is it trying to achieve?

I needed this while experimenting with a capi at #7562. But this might be useful for other usecases as well.

@ShaharNaveh ShaharNaveh requested a review from youknowone April 13, 2026 22:01
youknowone
youknowone approved these changes Apr 14, 2026
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Looks good, Thank you!

Hide details View details @youknowone youknowone merged commit 7544628 into RustPython:main Apr 14, 2026
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@bschoenmaeckers bschoenmaeckers deleted the pycapsule branch April 14, 2026 05:42
@coderabbitai coderabbitai Bot mentioned this pull request May 20, 2026
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@ShaharNaveh ShaharNaveh ShaharNaveh left review comments

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@youknowone youknowone youknowone approved these changes

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@bschoenmaeckers @youknowone @ShaharNaveh