test(amber): cover exportOperatorsAsZip and the remaining ResultExportService entry points

[eugenegujing]

What changes were proposed in this PR?

This PR extends amber/src/test/scala/org/apache/texera/web/service/ResultExportServiceSpec.scala (40 → 60 tests) to cover the three ResultExportService methods that previously had zero test references anywhere in the repository — exportOperatorsAsZip, exportSingleOperatorToDataset and getOperatorDocument — together with the edge cases of the export paths that reach them.

• exportOperatorsAsZip: throws WebApplicationException when the workflow never ran (where the sibling exportOperatorResultAsStream returns (null, None) for the same condition); names the archive <workflowName>-<yyyy-MM-dd_HH-mm-ss>.zip; dispatches each entry through the per-format writer on that operator's own outputType, with an unrecognised type falling back to CSV; routes every entry through NonClosingOutputStream so one entry's writer closing its stream cannot close the shared ZipOutputStream (asserted by a later entry surviving an earlier writer's close — the wrapper was already unit-tested in isolation, but nothing checked that the ZIP path uses it); and substitutes a <id>-empty.txt placeholder instead of aborting the archive, covered for both halves of the guard — an operator with no stored result URI, and an operator whose stored result table exists but holds zero rows.
• exportSingleOperatorToDataset (driven through exportToDataset): uploads each operator's rows to the file service in that operator's own format with the exact bodies asserted against a stub upload server, turns a thrown per-operator failure into an error entry instead of aborting the batch, reports a stored-but-empty result as having nothing to export, and pins the partial-success policy as characterization — when some operators export and some fail, the response is success carrying only the success lines.
• getOperatorDocument: returns null when the operator stored no result URI, opens the stored result document with its count and contents read back, and refuses a result stored in a per-user warehouse while the feature is off (WarehouseUnavailableException via the WarehouseReadGuard from [BYO-S3] Feature flag (storage.warehouse.enabled, default off) #6930).
• Edge cases along these paths: every row is written on both sides of the CSV chunk-buffer boundary (CHUNK_SIZE 10, exercised one-under, exactly-one and one-over); CSV values containing a comma, a double quote, a newline and non-ASCII text round-trip through the streamed export; streamCellData accepts the maximum row and column index and rejects the out-of-range ones with their exact reasons, while negative indexes are pinned as characterization because the >= guards let them through to an internal reader error and an array-index error; a result stored under an older execution is not exported once a newer execution exists, and the newer execution's rows win when both stored results; and requesting the same operator twice aborts the archive mid-stream with a duplicate-entry ZipException, pinned as characterization since the client has already received its 200 by then.

Tests that need actual rows open real Iceberg result tables, following the arrangement ExecutionResultServiceSpec already uses in amber unit tests. The section banner and class scaladoc described the request-level tests as stopping short of opening a result document, so they are updated to describe what these tests now do. No production code is changed.

Any related issues, documentation, discussions?

Closes #7814

How was this PR tested?

All changes are new or extended unit tests in ResultExportServiceSpec; run them with STORAGE_ICEBERG_CATALOG_TYPE=postgres sbt "WorkflowExecutionService/testOnly org.apache.texera.web.service.ResultExportServiceSpec" — 60 succeeded, 0 failed, and the suite was verified idempotent by running twice back-to-back against the same catalog database. Key assertions were mutation-checked by hand-editing production code and confirming that exactly the intended tests fail: replacing the NonClosingOutputStream wrapper with the raw stream, making the wrapper's close() close the underlying stream, skipping the empty-operator placeholder branch, dropping the zero-row half of both placeholder guards, forcing the ZIP dispatch to CSV, dropping the timestamp from the archive name, returning (null, None) instead of throwing when there is no execution, breaking the result-document lookup, removing the WarehouseReadGuard check, appending the dropped error lines to a partial-success response, cutting the CSV chunk loop to a single chunk, and resolving the oldest execution instead of the latest. Every mutation was reverted byte-exact afterwards, and scalafmtCheck passes.

Was this PR authored or co-authored using generative AI tooling?

Generated-by: Claude Code (Claude Fable 5, Claude Opus 5)

[github-actions]

Automated Reviewer Suggestions

Based on the git blame history of the changed files, we recommend the following reviewers:

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[github-actions]

⚠️ Benchmark changes need a look

🟢 4 better · 🔴 1 worse · ⚪ 10 noise (<±5%) · 0 without baseline

Compared against main 2edbdf9 benchmarked on this same runner, so the delta is largely free of cross-runner hardware noise. The "7d avg" column still reflects the gh-pages dashboard. Treat <±5% as noise unless repeated.

Dashboard · Run

	config	throughput	MB/s	latency	max Δ latest / 7d
🔴	bs=10 sw=10 sl=64	381	0.233	24,826/34,260/34,260 us	🟢 -31.4% / 🔴 +128.5%
🟢	bs=100 sw=10 sl=64	804	0.491	125,218/137,667/137,667 us	🟢 -19.7% / 🔴 +29.8%
⚪	bs=1000 sw=10 sl=64	925	0.565	1,076,062/1,146,346/1,146,346 us	⚪ within ±5% / 🔴 +13.5%

Baseline details

Latest main 2edbdf9 from same runner

config	metric	PR	latest main	7d avg	Δ latest	Δ 7d
bs=10 sw=10 sl=64	throughput	381 tuples/sec	388 tuples/sec	780.31 tuples/sec	-1.8%	-51.2%
bs=10 sw=10 sl=64	MB/s	0.233 MB/s	0.237 MB/s	0.476 MB/s	-1.7%	-51.1%
bs=10 sw=10 sl=64	p50	24,826 us	22,224 us	12,590 us	+11.7%	+97.2%
bs=10 sw=10 sl=64	p95	34,260 us	49,960 us	14,995 us	-31.4%	+128.5%
bs=10 sw=10 sl=64	p99	34,260 us	49,960 us	19,141 us	-31.4%	+79.0%
bs=100 sw=10 sl=64	throughput	804 tuples/sec	805 tuples/sec	1,006 tuples/sec	-0.1%	-20.1%
bs=100 sw=10 sl=64	MB/s	0.491 MB/s	0.491 MB/s	0.614 MB/s	0.0%	-20.0%
bs=100 sw=10 sl=64	p50	125,218 us	119,979 us	99,387 us	+4.4%	+26.0%
bs=100 sw=10 sl=64	p95	137,667 us	171,545 us	106,056 us	-19.7%	+29.8%
bs=100 sw=10 sl=64	p99	137,667 us	171,545 us	113,689 us	-19.7%	+21.1%
bs=1000 sw=10 sl=64	throughput	925 tuples/sec	912 tuples/sec	1,043 tuples/sec	+1.4%	-11.3%
bs=1000 sw=10 sl=64	MB/s	0.565 MB/s	0.557 MB/s	0.637 MB/s	+1.4%	-11.3%
bs=1000 sw=10 sl=64	p50	1,076,062 us	1,093,310 us	965,215 us	-1.6%	+11.5%
bs=1000 sw=10 sl=64	p95	1,146,346 us	1,138,790 us	1,009,610 us	+0.7%	+13.5%
bs=1000 sw=10 sl=64	p99	1,146,346 us	1,138,790 us	1,039,108 us	+0.7%	+10.3%

Raw CSV

config_idx,batch_size,schema_width,string_len,num_batches,total_ms,total_tuples,total_bytes,tuples_per_sec,mb_per_sec,lat_p50_us,lat_p95_us,lat_p99_us
0,10,10,64,20,524.55,200,128000,381,0.233,24826.10,34259.61,34259.61
1,100,10,64,20,2486.62,2000,1280000,804,0.491,125218.43,137667.15,137667.15
2,1000,10,64,20,21618.79,20000,12800000,925,0.565,1076061.97,1146346.35,1146346.35

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.37%. Comparing base (2edbdf9) to head (83e646c).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #7816      +/-   ##
============================================
- Coverage     91.50%   91.37%   -0.14%     
+ Complexity     4501     4475      -26     
============================================
  Files          1177     1169       -8     
  Lines         47489    47148     -341     
  Branches       5324     5288      -36     
============================================
- Hits          43457    43080     -377     
- Misses         2366     2405      +39     
+ Partials       1666     1663       -3     

Flag	Coverage Δ		*Carryforward flag
access-control-service	81.00% <ø> (ø)		Carriedforward from 9c5aecc
agent-service	98.62% <ø> (ø)		Carriedforward from 9c5aecc
amber	88.13% <ø> (+0.09%)	⬆️
computing-unit-managing-service	73.67% <ø> (ø)		Carriedforward from 9c5aecc
config-service	86.73% <ø> (ø)		Carriedforward from 9c5aecc
file-service	65.41% <ø> (-10.34%)	⬇️	Carriedforward from 9c5aecc
frontend	92.88% <ø> (-0.36%)	⬇️	Carriedforward from 9c5aecc
notebook-migration-service	78.86% <ø> (-0.28%)	⬇️	Carriedforward from 9c5aecc
pyamber	97.56% <ø> (-0.01%)	⬇️	Carriedforward from 9c5aecc
workflow-compiling-service	77.19% <ø> (ø)		Carriedforward from 9c5aecc

*This pull request uses carry forward flags. Click here to find out more.

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