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Frontend rejects /api/csv/preview reason "parse_failed" — T&E table suggestion silently lost #42
Description
Summary
When the server-side CSV parser throws, POST /api/csv/preview returns a structured error (the BUG-025 handler in api/routers/csv_routes.py):
{"status": "invalid_structure", "reason": "parse_failed", "message": "The CSV couldn't be parsed. Check the file's structure and try again."}The frontend's csvPreviewResultSchema (csv-table-hub-main/src/lib/csv.functions.ts) only allowed reason: "empty" | "header_only" | "no_columns". So previewCsv() failed zod validation and threw Unexpected response shape from /api/csv/preview: reason: Invalid enum value….
Impact
- In
Uploader.handleFiles(src/routes/_authenticated/index.tsx),previewCsvis only used for the best-effort T&E table suggestion, and the exception is swallowed bycatch { /* suggestion only */ }. - The visible effect: the user gets no T&E table suggestion and no explanation. The server's
messagenever reaches the UI. - It is a contract mismatch between API and frontend: a valid API response is treated as malformed.
Steps to reproduce
- Make the server parser throw on a file (in tests: patch
api.routers.csv_routes.build_previewto raise). - Call
previewCsv("p.csv", content)from the frontend, or upload the file through the UI. - Expected: the response is accepted with
reason: "parse_failed"and itsmessage. - Actual:
previewCsvthrows a schema error and the suggestion is silently dropped.
Notes
- Found by the new system-integration contract tests in Group tests into unit, system, SIT, performance, accessibility and UAT #41. They read the zod enums from
csv.functions.tsand check live API responses against them. - The fix belongs on the frontend:
parse_failedis an accurate reason and comes with a readable message, so the schema should accept it (plus the optionalmessage) rather than the API hiding it. - Fix commit:
15268aeon branchclaude/elegant-bohr-zn28zn(PR Group tests into unit, system, SIT, performance, accessibility and UAT #41).
Activity
test: regression tests for #42 (preview parse_failed) and #43 (CORS :…
amar-python commentedon Oct 10, 2026
Fixed and verified
Fix:
15268ae.csvPreviewResultSchemaincsv-table-hub-main/src/lib/csv.functions.tsnow acceptsreason: "parse_failed"and the optionalmessagethe API sends with it. The other reasons are unchanged, and unknown reasons are still rejected.Regression tests
csv-table-hub-main/src/__tests__/unit/preview-contract.test.ts(6 vitest cases, added in09ff668)previewCsv()with a mockedfetch.parse_failed+ message resolves with the message preserved;empty/header_only/no_columnsstill resolve; an unknown reason still throwsUnexpected response shape; the request goes to/api/csv/previewtests/system_integration/test_sit_frontend_contract.py::test_preview_parse_failure(SIT-18)parse_failedplus a message, and that reason is in the UI's preview enum (read from the TS source)tests/system_integration/test_sit_frontend_contract.py::test_preview_invalid_structure(SIT-17, 3 cases)invalid_structurereason the preview endpoint returns is also in the UI's enumThe tests catch the bug. Run against the pre-fix source (
15268ae~1):× accepts reason parse_failed and keeps the server message, failing with the exact error from this issue:Unexpected response shape from /api/csv/preview: reason: Invalid enum value. Expected 'empty' | 'header_only' | 'no_columns', received 'parse_failed'FAILED test_preview_parse_failurewithassert 'parse_failed' in {'empty', 'header_only', 'no_columns'}They pass with the fix:
6f6814a(PR Group tests into unit, system, SIT, performance, accessibility and UAT #41, all 4 checks green):accessibility (playwright + axe)job, vitest step:✓ src/__tests__/unit/preview-contract.test.ts (6 tests),Tests 101 passed (101).integration (postgres service)job:executed 392 · PASSED 392 · FAILED 0 · SKIPPED 0,RESULT: PASS. Its 23 "not run" tests are only the accessibility ones, so SIT-17/18 are among the 392 that passed.Note: the fix is on branch
claude/elegant-bohr-zn28znand reachesmainwhen PR #41 is merged.Closing as fixed.
Generated by Claude Code
Merge pull request #74 from amar-python/fix/issues-42-43-on-main