fix(cli): drop the value of unsupported go test flags by not-matthias · Pull Request #67 · CodSpeedHQ/codspeed-go

not-matthias · 2026-10-29T18:28:40Z

TLDR: Unsupported go test flags were dropped, but their separate value became a package: go test -p 1 ./... -bench . failed with package 1 is not in std after the benchmarks ran. The parser now knows each Go flag's arity and drops the value too.

Go flags take 0 or 1 values, so cli.rs keeps the boolean (20) and value (47) flag lists from cmd/go (Go 1.24 to 1.27).
Boolean flags (-v, -race) drop only themselves; test -v fmt keeps fmt.
Value flags drop the next argument, even if it starts with - (-ldflags "-s -w").
Flags unknown to go test (custom test flags) drop the next argument unless it starts with -, like Go.
Unsupported flags still only warn (log::warn!); the run never fails before Go is invoked.

Review note: the flag lists need an update when Go adds go test or build flags.

Closes COD-4005

codspeed · 2026-10-29T18:40:34Z

Merging this PR will degrade performance by 15.49%

3 warnings

⚠️ Walltime results may be unreliable

Some benchmarks used the Walltime instrument outside CodSpeed Macro Runners, which can make the results inconsistent.

Learn more about Macro Runners

See affected benchmarks

⚠️ Unable to measure the execution of 1 benchmark

This benchmark measured no execution time, so its result is not comparable and counts as unchanged. This usually happens when the compiler removes the code under test.

Prevent compiler optimizations

See affected benchmarks

⚠️ 1 benchmark with a significant change ran on different hardware

Its base and head results were measured on machines with a different CPU, core count or memory, so the change might not come from the code. Run base and head on the same runner type.

Learn more about Macro Runners

See affected benchmarks

❌ 1 regressed benchmark
✅ 49 untouched benchmarks
⏩ 1 skipped benchmark¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Benchmark	`BASE`	`HEAD`	Efficiency
❌	`BenchmarkFibonacciDarwin`	224.2 µs	265.3 µs	-15.49%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

_{Comparing cod-4005-handle-unsupported-go-runner-flags-without-leaving-orphaned (a8f4f19) with main (84ece6e)}

1 benchmark was skipped, so the baseline result was used instead. If it was deleted from the codebase, click here and archive it to remove it from the performance reports. ↩

greptile-apps · 2026-10-30T18:23:59Z

Confidence Score: 4/5

[Medium impact] The change affects command-line parsing across Go runner benchmark runs.

Fix unsupported flag rejection and use tracing for the added warning before merging.

Findings

Flags change package selection ▶
Warning bypasses tracing ▶

Fix with agent prompt

### Issue 1
go-runner/src/cli.rs:133-139
With `test -v fmt`, the new code consumes `fmt` as a flag value and runs the default `./...` instead of the requested package. Conversely, `test -cpuprofile ./cpu.out ./...` keeps `./cpu.out` as a package, leaving the original failure unfixed.

Return `CliExit::UnknownFlag` before Go runs, as the PR description requires, rather than guessing which arguments belong to unsupported flags. Update the tests to expect rejection.

### Issue 2
go-runner/src/cli.rs:140
The new warning uses `eprintln!`, but the repository rule prohibits `println!` and `eprintln!` in Rust and requires tracing macros instead. Use `tracing::warn!` here to satisfy that requirement before merging.

```suggestion
                        tracing::warn!("ignoring value '{value}' of unsupported flag '{s}'");
```

Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!

---

For each issue above, determine whether it is valid and should be fixed. If so, fix it directly.

Summary

The PR adds a helper that guesses whether an argument is a package and skips presumed values of unsupported flags.

The parser keeps many unsupported flag values out of the package list.

_{Reviews (1) · Last reviewed commit: "fix(cli): drop the value of unsupported ..." · Reviewed by Greptile}

lvaroqui

LGTM! 🎸

The parser warned about unsupported flags but dropped only the flag, so a separate value was collected as a package. In `go test -p 1 ./... -bench .`, `1` became a package and the run failed with `package 1 is not in std` after the benchmarks completed. Unsupported flags are now classified the way `go test` parses them. Go flags take either no value (booleans such as `-v` or `-race`) or exactly one (`-p 1`, `-p=1`), so the runner keeps both lists from cmd/go. Boolean flags drop only themselves; value flags also drop the next argument, even when it starts with `-` (`-ldflags "-s -w"`). Flags unknown to `go test`, such as custom test flags, drop the next argument unless it starts with `-`, like Go does. The run keeps going and never fails before Go is invoked. Closes COD-4005

not-matthias force-pushed the cod-4005-handle-unsupported-go-runner-flags-without-leaving-orphaned branch from 52a0d05 to 0458739 Compare October 30, 2026 18:20

not-matthias marked this pull request as ready for review October 30, 2026 18:20

not-matthias requested a review from lvaroqui October 30, 2026 18:21

greptile-apps Bot reviewed Oct 30, 2026

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Comment thread go-runner/src/cli.rs Resolved

Comment thread go-runner/src/cli.rs Resolved

lvaroqui reviewed Nov 2, 2026

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Comment thread go-runner/src/cli.rs Resolved

not-matthias force-pushed the cod-4005-handle-unsupported-go-runner-flags-without-leaving-orphaned branch from 0458739 to f865954 Compare November 2, 2026 14:28

not-matthias changed the title ~~fix(cli): reject unsupported go test flags~~ fix(cli): drop the value of unsupported go test flags Nov 2, 2026

not-matthias force-pushed the cod-4005-handle-unsupported-go-runner-flags-without-leaving-orphaned branch 2 times, most recently from 0f92d26 to b28e471 Compare November 2, 2026 14:34

not-matthias requested a review from lvaroqui November 2, 2026 14:35

lvaroqui approved these changes Nov 2, 2026

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not-matthias force-pushed the cod-4005-handle-unsupported-go-runner-flags-without-leaving-orphaned branch from b28e471 to a8f4f19 Compare November 2, 2026 17:44

not-matthias merged commit c64fb9b into main Nov 2, 2026
22 of 23 checks passed

not-matthias deleted the cod-4005-handle-unsupported-go-runner-flags-without-leaving-orphaned branch November 2, 2026 17:54

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fix(cli): drop the value of unsupported go test flags - #67

fix(cli): drop the value of unsupported go test flags#67
not-matthias merged 1 commit into
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Merging this PR will degrade performance by 15.49%

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Confidence Score: 4/5

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