UI: Return 400 instead of 500 from structure_data on malformed asset_expression

[dkranchii]

The /structure/structure_data endpoint calls get_upstream_assets() to walk the serialized Dag's asset_expression. If the stored expression contains an unknown key (anything other than any / all) or an unknown asset type (anything other than asset / asset-alias / asset-name-ref / asset-uri-ref), get_upstream_assets() raises TypeError("Unsupported type: ...") at services/ui/structure.py:69 or :102.

The exception escaped uncaught and FastAPI returned a generic {"detail": "Internal Server Error"} response body with no context about which Dag triggered it. Operators had to dig through server logs to identify the broken Dag — a frustrating debugging loop for a multi-Dag deployment.

This wraps the call in try/except TypeError and re-raises as HTTPException(400) with a detail message identifying the Dag id and version. It remains a 400 because the underlying issue is genuinely server-side stored-data corruption (not bad client input — the request is valid). The improvement is the response body: it's now controlled, documented, and debuggable.

Before

GET /structure/structure_data?dag_id=foo&external_dependencies=True → 500 Internal Server Error {"detail": "Internal Server Error"}

After

GET /structure/structure_data?dag_id=foo&external_dependencies=True → 400 Internal Server Error {"detail": "Malformed asset_expression in Dag 'foo' version 3: Unsupported type: dict_keys(['weird-op'])"}

Tests

Adds TestStructureDataEndpoint::test_should_return_400_on_malformed_asset_expression which mocks get_upstream_assets to raise TypeError and asserts the response surfaces a 400 with a detail message that names the Dag and includes the wrapped error.

Related

• AGENTS.md rule added in AGENTS.md: require translating domain-layer exceptions to HTTPException at FastAPI route boundaries #67221: "Translate domain-layer exceptions to HTTPException at FastAPI route boundaries." This PR conforms to that rule by replacing an uncaught domain exception with a controlled HTTPException response.
• Sibling PR: UI: Fix HTTPException import that turned a 400 into a 500 in ui/dags  #67363 addressed the same class of bug in ui/dags.py.

---

Was generative AI tooling used to co-author this PR?

• Yes — (Cursor) used for review and verify.

[jason810496]

We should just re-raise the TypeError exception as HTTPException. It's fine to add more context to the exception, but we should correct the response code anyway.

airflow/airflow-core/src/airflow/api_fastapi/core_api/services/ui/structure.py

Lines 57 to 69 in 0a2f181

	ifexpr_keyinasset_expression:
	asset_exprs: list[dict] =asset_expression[expr_key]
	forexprinasset_exprs:
	nested_expr_key=next(iter(expr.keys()))
	ifnested_expr_keyin ("any", "all"):
	nested_expression=expr
	elifnested_expr_keyin ("asset", "alias", "asset-name-ref", "asset-uri-ref"):
	asset_info=expr[nested_expr_key]
	asset_info["type"] =nested_expr_keyifnested_expr_key!="alias"else"asset-alias"
	assets_info.append(asset_info)
	else:
	raiseTypeError(f"Unsupported type: {expr.keys()}")

[jason810496]

Please fix the static check failure, thanks.

[pierrejeambrun]

LGTM thanks

[pierrejeambrun]

CI still needs fixing. You can take a look at our contributing doc which explains how to run those locally. (pre-commit hooks etc...) if you want to reproduce locally.

[dkranchii]

@pierrejeambrun pls review.

[choo121600]

overall looks good :)
one nit

[pierrejeambrun]

Unrelated CI failure, merging.

[github-actions]

Backport successfully created: v3-2-test

Note: As of Merging PRs targeted for Airflow 3.X
the committer who merges the PR is responsible for backporting the PRs that are bug fixes (generally speaking) to the maintenance branches.

In matter of doubt please ask in #release-management Slack channel.

Status	Branch	Result
✅	v3-2-test