fix(codegen): allow custom scalars from scalar_map without explicit python type (#4741) by Rajan-vish · Pull Request #4789 · strawberry-graphql/strawberry

Rajan-vish · 2026-11-03T20:34:36Z

Description

When custom scalars are mapped via StrawberryConfig(scalar_map={...}) or have ScalarDefinition without an explicit ScalarWrapper, _get_field_type in QueryCodegen was discarding the original Python type and passing None to _collect_scalar. This caused PythonPlugin._print_scalar_type to fail with:
AssertionError: Scalar type must have a python type:
and TypeScriptPlugin to fail with KeyError or assertion errors.

Solution

In strawberry/codegen/query_codegen.py:
- Preserve original_python_type from ield_type before scalar registry replacement.
- For ScalarDefinition, if original_python_type is None, look up the matching scalar in self.schema.schema_converter.scalar_registry or fallback to ield_type.origin.
- Unwrap supertype (e.g. for NewType).
In strawberry/codegen/plugins/python.py:
- Safely resolve the scalar's Python type and add module imports (skipping builtins/main).
- Gracefully fallback to Any if python_type is None.
In strawberry/codegen/plugins/typescript.py:
- Map ype_.python_type via SCALARS_TO_TS_TYPE with a fallback to �ny.
In ests/codegen/test_query_codegen.py:
- Added unit tests covering custom scalars mapped via StrawberryConfig.scalar_map in both return types and input variables for Python and TypeScript codegen.
Added RELEASE.md for patch release changelog.

Types of Changes

Bug fix (non-breaking change which fixes an issue)
New feature (non-breaking change which adds functionality)
Breaking change (fix or feature that would cause existing functionality to change)
Documentation update

Checklist

I have read the CONTRIBUTING doc
I have added tests to cover my changes
All new and existing tests passed
I have added entries to RELEASE.md

Summary by Sourcery

Fix client code generation for custom scalars by preserving their underlying Python types and falling back gracefully when type information is unavailable.

Bug Fixes:

Prevent code generation from failing for custom scalars registered through scalar maps or without explicit Python types.
Provide safe Python and TypeScript fallbacks for scalars whose underlying types cannot be resolved.

Enhancements:

Preserve and deduplicate custom scalar Python type information across generated client types.
Handle None-based scalars and unwrap NewType definitions during code generation.

Documentation:

Add a patch release note describing the custom scalar code generation fix.

Tests:

Add coverage for custom scalar return types, input variables, deduplication, void scalars, and unmapped scalar fallbacks in Python and TypeScript code generation.

…ython type (strawberry-graphql#4741)

github-actions · 2026-11-03T20:35:11Z

Thanks for adding the RELEASE.md file!

Below is the changelog that will be used for the release.

This release fixes an issue where running strawberry codegen crashed with
AssertionError: Scalar type must have a python type when custom scalars were
registered via StrawberryConfig.scalar_map.

QueryCodegen now correctly preserves and propagates the custom scalar's underlying
Python type (or falls back to Any when unmapped) when generating Python and
TypeScript client types.

This release was contributed by @Rajan-vish in #4789

greptile-apps · 2026-11-03T20:39:05Z

Confidence Score: 3/5

[Medium impact] The changes affect the bounded workflow that generates Python and TypeScript client types.

Fix duplicate TypeScript aliases and undefined NoneType references before merging.

Findings

TypeScript aliases repeat ▶
Generated Python references undefined `NoneType` ▶

Summary

Fixes custom scalar code generation by retaining Python types from scalar_map.

Codegen carries custom scalar types into Python and TypeScript output.

Diagram

%%{init: {'theme': 'neutral'}}%%
flowchart LR
  A[Field or variable] --> B[Resolve scalar definition]
  B --> C[Find underlying Python type]
  C --> D[Collect scalar]
  D --> E[Python alias and imports]
  D --> F[TypeScript alias]

_{Reviews (1) · Last reviewed commit: "fix(codegen): allow custom scalars from ..." · Reviewed by Greptile}

greptile-apps · 2026-11-03T20:39:08Z

            not isinstance(field_type, StrawberryType)
            and field_type in self.schema.schema_converter.scalar_registry
        ):
+            original_python_type = field_type


TypeScript aliases repeat

Preserving each field's Python type can generate the same TypeScript alias twice. Mapping str and float to one scalar definition named Custom is accepted by the schema converter. Selecting fields of both types now collects two different GraphQLScalar objects and emits both type Custom = string and type Custom = number. TypeScript rejects the duplicate name.

Choose one Python type per scalar definition and reuse it for fields and variables.

Addressed in commit 341a604 by caching GraphQLScalar in self._scalar_definitions by scalar name in QueryCodegen._collect_scalar, ensuring each scalar definition is collected once and reused across all fields and variables without duplicate alias generation.

greptile-apps · 2026-11-03T20:39:08Z

+                type_name = type_.python_type.__name__
+                if hasattr(
+                    type_.python_type, "__module__"
+                ) and type_.python_type.__module__ not in ("builtins", "__main__"):
+                    self.imports[type_.python_type.__module__].add(type_name)


Generated Python references undefined NoneType

A field returning None resolves to the registered Void scalar with python_type=type(None). This branch emits Void = NewType("Void", NoneType) but skips its import because its module is builtins. NoneType is not a built-in name, so importing the generated file raises NameError.

Import NoneType from types, or print type(None) instead.

Addressed in commit 341a604 by importing NoneType from types when type_.python_type is type(None), and mapping type(None) to null in TypeScript.

sourcery-ai

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

Sourcery assessment

Approved.

Sourcery is free for open source - if you like our reviews please consider sharing them ✨

…Void scalar

sourcery-ai

Linked issues

#4741 codegen: allow mapping custom scalars to Python types (`Scalar type must have a python type`) · 1 of 3 met

#	Requirement	Status	Notes
1	Prevent codegen from aborting on custom scalars registered through StrawberryConfig.scalar_map.	✅ Met	QueryCodegen preserves or recovers the scalar's Python type, and the plugins fall back to Any/any when no type is available.
2	Allow scalar names to be mapped to Python annotations through the CLI or a config file.	❌ Not addressed	The change uses types already present in the schema's scalar registry; it adds no CLI or config-file mapping for scalar names to annotations.
3	Fall back to Any for an unmapped scalar with a warning instead of raising an assertion.	🟡 Partly met	Python codegen falls back to Any, but it does not emit a warning.

…trawberry-graphql#4741)

fix(codegen): allow custom scalars from scalar_map without explicit p…

11f18ab

…ython type (strawberry-graphql#4741)

greptile-apps Bot reviewed Nov 3, 2026

View reviewed changes

sourcery-ai Bot approved these changes Nov 3, 2026

View reviewed changes

fix(codegen): deduplicate scalar definitions and import NoneType for …

341a604

…Void scalar

sourcery-ai Bot reviewed Nov 4, 2026

View reviewed changes

Comment thread strawberry/codegen/plugins/python.py Resolved

feat(codegen): emit warning when unmapped scalar falls back to Any (s…

b6a8cac

…trawberry-graphql#4741)

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fix(codegen): allow custom scalars from scalar_map without explicit python type (#4741) - #4789

fix(codegen): allow custom scalars from scalar_map without explicit python type (#4741)#4789
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Rajan-vish:fix-query-codegen-scalar-map-4741

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Description

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Types of Changes

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Summary by Sourcery

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Confidence Score: 3/5

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