Patch default injection for annotated fields

[jacobmoshipco]

Important

This PR is still a draft as I will not have time to write tests for the change for awhile.
Help in this regard would be appreciated.

Description

This patch fixes a bug where input strawberry.Maybe input fields would fail to have a default None injected when annotated or set with strawberry.field.

Previously, this would cause this example input to require name to be set, despite it being marked Maybe

@strawberry.input
class Example:
    name: strawberry.Maybe[str] = strawberry.field(description="This strawberry.field annotation was breaking in default injection")

Types of Changes

• Core
• Bugfix
• New feature
• Enhancement/optimization
• Documentation

Issues Fixed or Closed by This PR

• Default None is not being injected in Maybe annotations when the attribute is annotated #3962

Checklist

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• I have tested the changes and verified that they work and don't break anything (as well as I can manage).

Summary by Sourcery

Fix default None injection for input fields annotated with strawberry.Maybe and improve detection of Maybe annotations

Bug Fixes:

• Ensure default None is injected for fields with Maybe annotations even when defined via strawberry.field

Enhancements:

• Support unwrapping Annotated types in the Maybe annotation detection logic

[sourcery-ai]

Reviewer's guide (collapsed on small PRs)

Reviewer's Guide

This patch refines the default-injection mechanism for fields annotated with Maybe by ensuring that None is applied even when using strawberry.field, and it augments the annotation detection to recognize Maybe nested within Annotated types.

File-Level Changes

Change	Details	Files
Refined default injection for Maybe-annotated fields with StrawberryField instances	Preserve existing injection behavior when no attribute is present Add branch to detect StrawberryField with missing default and default_factory Assign None to attr.default when both default markers are _MISSING_TYPE	types/object_type.py
Extended _annotation_is_maybe to handle Annotated wrappers	Import Annotated from typing Check for Annotated origin and unwrap its first argument Recursively call _annotation_is_maybe on the unwrapped type	types/maybe.py

Possibly linked issues

• Default None is not being injected in Maybe annotations when the attribute is annotated #3962: The PR updates _annotation_is_maybe to support Annotated types and modifies _inject_default_for_maybe_annotations to inject None for Maybe fields, directly resolving the bug.
• Default None is not being injected in Maybe annotations when the attribute is annotated #3962: PR injects None for strawberry.Maybe input fields, addressing issue Default None is not being injected in Maybe annotations when the attribute is annotated #3962's request for optional type default behavior.

---

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[sourcery-ai]

Hey there - I've reviewed your changes and they look great!

Prompt for AI Agents

Please address the comments from this code review:
## Individual Comments

### Comment 1
<location> `strawberry/types/object_type.py:137` </location>
<code_context>
+                setattr(cls, name, None)
+            elif (
+                isinstance(attr := getattr(cls, name), StrawberryField)
+                and isinstance(attr.default, dataclasses._MISSING_TYPE)
+                and isinstance(attr.default_factory, dataclasses._MISSING_TYPE)
+            ):
</code_context>

<issue_to_address>
Using dataclasses._MISSING_TYPE is relying on a private API.

Use dataclasses.MISSING instead, as it is the public API and more stable across Python versions.
</issue_to_address>

---

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[sourcery-ai]

issue: Using dataclasses._MISSING_TYPE is relying on a private API.

Use dataclasses.MISSING instead, as it is the public API and more stable across Python versions.

[greptile-apps]

Greptile Summary

This PR fixes a bug in Strawberry GraphQL's handling of strawberry.Maybe input fields when they are explicitly defined using strawberry.field(). The core issue was that Maybe fields with field annotations or descriptions would incorrectly be treated as required fields instead of optional ones with default None values.

The fix involves two complementary changes:

1. Enhanced Maybe detection (maybe.py): The _annotation_is_maybe() function now recursively handles typing.Annotated wrappers, which are created when using strawberry.field() with descriptions or other metadata. Previously, the function would fail to recognize Maybe types when they were wrapped in Annotated.

2. Improved default injection (object_type.py): The _inject_default_for_maybe_annotations() function now handles cases where a StrawberryField object already exists on the class but lacks explicit default values. The function checks for StrawberryField instances where both default and default_factory are missing and injects None as the default value.

This change preserves the existing behavior for simple Maybe field declarations (e.g., name: strawberry.Maybe[str]) while extending support to field-annotated Maybe types (e.g., name: strawberry.Maybe[str] = strawberry.field(description="...")). The fix ensures that Maybe semantics work consistently across different field definition styles in input types, which is crucial for the GraphQL schema's type system integrity.

Confidence score: 4/5

• This PR addresses a specific bug with a targeted fix that should be safe to merge with minimal risk
• Score reflects well-isolated changes to core type handling logic, though the lack of tests in the current PR reduces confidence slightly
• Pay close attention to the Maybe type detection logic and default injection mechanisms, as these are foundational to input type behavior

_{2 files reviewed, 1 comment}

_{Edit Code Review Bot Settings | Greptile}

[botberry]

Hi, thanks for contributing to Strawberry 🍓!

We noticed that this PR is missing a RELEASE.md file. We use that to automatically do releases here on GitHub and, most importantly, to PyPI!

So as soon as this PR is merged, a release will be made 🚀.

Here's an example of RELEASE.md:

Release type: patch

Description of the changes, ideally with some examples, if adding a new feature.

Release type can be one of patch, minor or major. We use semver, so make sure to pick the appropriate type. If in doubt feel free to ask :)

Here's the tweet text:

🆕 Release (next) is out! Thanks to jacobmoshipco for the PR 👏

Get it here 👉 https://strawberry.rocks/release/(next)

[codspeed-hq]

CodSpeed Performance Report

Merging #3985 will not alter performance

_{Comparing jacobmoshipco:patch-maybe-default-injection (f09af16) with main (58ea8c9)}

Summary

✅ 26 untouched benchmarks