[mikebridge]

SUMMARY

TL;DR: Metric discovery reports an access refusal instead of showing a misleading empty or incomplete catalog.

Background. MCP clients use list_metrics to find metrics across datasets and semantic views.

Problem. If a semantic view refused discovery while loading metrics or compatible dimensions, the per-view fallback swallowed that refusal and reported a successful result. Clients could mistake missing metrics for an empty catalog.

What changes. Typed security refusals reach the existing AccessDenied handler. If any visible view refuses discovery, an unscoped list_metrics call fails as a whole, including built-in dataset metrics; use dataset_id or view_id to scope the call to a source that does not refuse. Unexpected provider failures keep their warning and partial-result behavior. Tests cover scoped and unscoped discovery through streamable HTTP, plus refusal responses on both async chart-data HTTP paths. No SDK or /compatible behavior changes.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

Not applicable: MCP and HTTP response behavior.

TESTING INSTRUCTIONS

Run pytest tests/unit_tests/mcp_service/semantic_layer/tool/test_list_metrics.py tests/unit_tests/semantic_layers/query_errors_test.py -q.

143 tests passed. Six discovery cases fail on the old code and pass with the fix. Both async HTTP cases fail when refusals are deliberately converted to 202 responses; the production async implementation is unchanged. Changed-file hooks pass.

HTTP tests use in-process transports and injected refusal exceptions. They do not require or validate a live provider, broker or worker.

ADDITIONAL INFORMATION

• Has associated issue:
• Required feature flags: SEMANTIC_LAYERS for semantic-view discovery
• Changes UI
• Includes DB Migration
• Introduces new feature or API
• Removes existing feature or API

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.73%. Comparing base (9e4292e) to head (aba100c).
⚠️ Report is 9 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #45905   +/-   ##
=======================================
  Coverage   84.73%   84.73%           
=======================================
  Files        3069     3069           
  Lines      205771   205792   +21     
  Branches    48396    48399    +3     
=======================================
+ Hits       174354   174378   +24     
+ Misses      28123    28122    -1     
+ Partials     3294     3292    -2     

Flag	Coverage Δ
hive	34.50% <0.00%> (-0.01%)	⬇️
mysql	52.60% <0.00%> (-0.01%)	⬇️
postgres	52.60% <0.00%> (-0.01%)	⬇️
presto	36.23% <0.00%> (-0.01%)	⬇️
python	87.76% <100.00%> (+<0.01%)	⬆️
sqlite	52.37% <0.00%> (-0.01%)	⬇️
unit	82.52% <100.00%> (+<0.01%)	⬆️

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