feat(runner): write a screenshot to stdout with --out - - #1578
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feat(runner): write a screenshot to stdout with --out -#1578Goran Gajic (gorangajic) wants to merge 5 commits into
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`qawolf runner screenshot` only wrote a file, so a caller that wants the bytes in a process reserved a path, ran the command, read the file back and deleted it on every computer-use step. `--out -` writes the decoded JPEG to stdout instead, the same `-` that reads stdin for act and exec. Stdout then carries the image alone: the confirmation, and the JSON line under --json, moves to stderr so nothing follows the bytes into a reader that takes stdout as the file.
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Under Node a write to a closed pipe reports EPIPE twice: to the write callback, and as an error event a tick later. With no listener the event is an uncaught exception, so the unwritable answer the writer had just produced was followed by a crash and exit 1. The listener now goes on before the write and comes off only after a success. The test doubles are real Writable streams, since an object with only a write method never emits the event and hid the crash.
Only a terminal on stdout selects human mode, and a terminal cannot read JPEG bytes; the confirmation would also land among them, since clack prints to stdout, rather than on stderr as the message promises.
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Relates to WIZ-11974
Overview of Changes
qawolf runner screenshotonly wrote a file. The Tester session, which wants the bytes in a process, had to reserve a temp path, hand it to the sandboxed user, run the command, read the file back and delete it on every computer-use step.--out -now writes the decoded JPEG to stdout, the same-that already means stdin foractandexec. Stdout carries the image alone: the confirmation, and the JSON line under--json, goes to stderr so nothing follows the bytes into a reader that treats stdout as the file. A terminal on stdout is refused, since nothing there can read the bytes. The help text, the runner guide and the skill say so.Raw bytes rather than a base64 field in the JSON answer, because the repo's rule is to decode next to the write so nobody files base64 text as a JPEG, and because a byte stream is what a reader that pipes the command into a file or a viewer expects.
Testing
bun run typecheck bun run lint bun run format:check bun run knip bun run test bun run buildAdded tests: the writer sends decoded bytes to stdout and nothing to disk, refuses a non-JPEG answer for stdout too, and reports a closed pipe without letting the stream's error event crash the process (the doubles are real Writable streams for that reason); the handler keeps every confirmation off stdout in json and agent mode, refuses a terminal on stdout, and names stdout rather than a file when the pipe fails.
Checklist
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