Fix: needs_schema_definitions_from_json triggers full rebuild on every incremental build

[vanhci]

Summary

Bug: When needs_schema_definitions_from_json is set, every incremental sphinx-build rebuilds ALL documents because Sphinx detects a spurious [config changed ('needs_schema_definitions')].

Root Cause: resolve_schemas_config is connected to env-before-read-docs, and via populate_field_type mutates needs_config.schema_definitions['schemas'] in place — injecting "type": "string" / "object" etc. into every nested schema. This event fires AFTER Sphinx's config-inited config-change checkpoint:

1. config-inited — schemas.json loaded → {"const": "role"}
2. Sphinx compares pickled config vs in-memory config ← still sees {"const": "role"}
3. env-before-read-docs → populate_field_type mutates in place → {"const": "role", "type": "string"}
4. End of build → pickle persists the mutated config

Next build: step 2 compares fresh JSON ({"const": "role"}) vs pickled mutated config ({"const": "role", "type": "string"}) → mismatch → full rebuild → permanent loop.

Fix: In resolve_schemas_config, deep-copy each schema with copy.deepcopy() before passing it to populate_field_type(), so the original config remains unchanged and the pickled config matches the fresh load.

Changes

• File: sphinx_needs/schema/config_utils.py
• Lines: Added import copy at line 5, modified resolve_schemas_config() (around line 103) to pass copy.deepcopy(schema) instead of schema directly to populate_field_type()

Testing

The fix was verified by understanding the mutation flow: populate_field_type injects type fields into schemas, and by deep-copying before mutation, the original pickled config remains identical across builds.

Fixes #1711

[ubmarco]

Thanks for the PR.
Closed in favor of #1712
Will release this today.

[ubmarco]

Release is out!