[VanditGupta]

Fixes #431

Summary

sort_by() rejected embedded model fields: validate_sort_fields only looked at the model's top-level fields, so sort_by("metrics__score") and sort_by("metrics.score") both raised QueryNotSupportedError ("that field does not exist on the model"), even though find() on the same field works.

This adds a small _resolve_sort_field helper that accepts parent__child or parent.child, walks the same ExpressionProxy chain find() uses, and returns the field plus its RediSearch name (<parent>_<child>, e.g. metrics_score). Validation uses it for the existing sortable/indexed checks, and resolve_redisearch_sort_fields uses it for the SORTBY name. Top-level fields and the KNN score field behave as before. A path to a field that doesn't exist, or one that is neither sortable nor indexed, still raises QueryNotSupportedError.

Added test_sorting_on_embedded_field in tests/test_json_model.py: ascending and descending order with both separators, the generated SORTBY arguments, and both error cases. Only the async code and tests are edited; the sync versions are generated by make sync.

Testing

Run in a Linux Docker container with redis/redis-stack-server, on this branch:

• The new test passes in tests/ and in the generated tests_sync/. On the unmodified code it fails with the error from the issue.
• tests/ and tests_sync/: everything passes except test_cli_migrate.py (2 tests in each directory). Those fail the same way without this change, because the CLI subprocess in my setup cannot reach Redis.
• ruff check, ruff format --check and mypy (the make lint commands) pass.

Not run: make test itself (I ran pytest directly against one Redis Stack instance, without -n auto or coverage), make test_oss against OSS Redis, and nested paths deeper than one embedded level.

AI assistance

This change was drafted with an AI coding assistant (Claude) and then reviewed by me.

• I read this diff and collaborated with the Claude agent on it
• I ran the tests myself and attached proof in this PR where required
• I checked the project's current contribution and AI policy

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Note

Low Risk
Localized query-layer change with tests; behavior for top-level sort fields and KNN is preserved.

Overview
sort_by() now accepts embedded JsonModel field paths (metrics__score or metrics.score), matching what find() already supports on nested fields.

FindQuery gains _resolve_sort_field, which walks the same ExpressionProxy chain as filter expressions and maps paths to RediSearch index names (e.g. metrics_score). validate_sort_fields and resolve_redisearch_sort_fields use it for existence/sortable checks and SORTBY args; top-level fields and KNN score sorting are unchanged. Invalid or non-sortable embedded paths still raise QueryNotSupportedError.

Adds test_sorting_on_embedded_field for asc/desc order, SORTBY resolution, and error cases.

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