[rayapp] rayapp: split stdout and stderr tailwriter

[elliot-barn]

rayapp/anyscale_cli.go — Split the single tailWriter into separate
stdoutBuf and stderrBuf. Only stdout is returned as the parsed output.
On error, stderr is included in the error message for diagnostics.

rayapp/anyscale_cli_test.go — Updated the "command fails with stderr"
test case to expect stderr content in the error string instead of in
the returned output. Added TestRunAnyscaleCLI_StderrNotInOutput that
verifies a [WARNING] on stderr doesn't leak into the parsed output.

Tested locally with rayapp test service-intro on anyscale==0.26.81

partial log of successful anyscale cli commands with [WARNING] messages

(anyscale +58.9s) Workspace 'expwrk_jegme97wcmdsmg9pejnp184eqd' reached target state, exiting >>> anyscale workspace_v2 push --name service-intro-20260324182301 --local-dir /tmp/template_zip4143637084 [WARNING] A newer version of the Anyscale CLI is available. Your current version is 0.26.81. The latest version is 0.26.91. To avoid issues accessing Anyscale`s API, upgrade to the latest version by running `pip install --upgrade anyscale`. Detected files that exist in the destination but not in the source. The files will not be deleted by default. You can add '--delete' option to delete the files: .anyscaleignore >>> anyscale workspace_v2 run_command --name service-intro-20260324182301 unzip -o service-intro.zip [WARNING] A newer version of the Anyscale CLI is available. Your current version is 0.26.81. The latest version is 0.26.91. To avoid issues accessing Anyscale`s API, upgrade to the latest version by running `pip install --upgrade anyscale`. Archive: service-intro.zip inflating: README.ipynb inflating: README.md inflating: assets/service-logs.png inflating: assets/service-overview.png inflating: assets/service-replicas.png inflating: assets/service-rollout.png inflating: main.py >>> anyscale workspace_v2 push --name service-intro-20260324182301 --local-dir /tmp/test_zip1617622678 [WARNING] A newer version of the Anyscale CLI is available. Your current version is 0.26.81. The latest version is 0.26.91. To avoid issues accessing Anyscale`s API, upgrade to the latest version by running `pip install --upgrade anyscale`. Detected files that exist in the destination but not in the source. The files will not be deleted by default. You can add '--delete' option to delete the files: assets/service-rollout.png assets/service-replicas.png assets/service-overview.png assets/service-logs.png assets/ service-intro.zip main.py README.md README.ipynb .anyscaleignore >>> anyscale workspace_v2 run_command --name service-intro-20260324182301 unzip -o tests.zip [WARNING] A newer version of the Anyscale CLI is available. Your current version is 0.26.81. The latest version is 0.26.91. To avoid issues accessing Anyscale`s API, upgrade to the latest version by running `pip install --upgrade anyscale`. Archive: tests.zip inflating: tests.sh >>> anyscale workspace_v2 run_command --name service-intro-20260324182301 timeout 900 bash -c 'bash tests.sh' [WARNING] A newer version of the Anyscale CLI is available. Your current version is 0.26.81. The latest version is 0.26.91. To avoid issues accessing Anyscale`s API, upgrade to the latest version by running `pip install --upgrade anyscale`.

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request refactors the runAnyscaleCLI function to distinctly handle stdout and stderr streams. This change is vital for applications that parse the command-line interface's output, as it prevents diagnostic messages or warnings from stderr from interfering with structured data returned on stdout. While both streams are still displayed to the user, the programmatic capture now isolates stdout, leading to more robust parsing and clearer error reporting.

Highlights

• Separated Output Streams: The runAnyscaleCLI function now captures stdout and stderr independently using separate tailWriter buffers, ensuring distinct handling of each stream.
• Clean Structured Output: The function's return value now exclusively contains stdout content, preventing structured output (e.g., JSON/YAML) from being corrupted by stderr messages.
• Enhanced Error Reporting: Error messages generated by runAnyscaleCLI now include the full content of stderr, providing more comprehensive context when a command fails.
• Improved Test Coverage: A new test case, TestRunAnyscaleCLI_StderrNotInOutput, was added to specifically verify that stderr content does not appear in the returned stdout, ensuring the integrity of structured output.

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[gemini-code-assist]

Code Review

This pull request refactors the runAnyscaleCLI function to explicitly separate stdout and stderr streams. Previously, both streams were combined, which could lead to issues when parsing structured output from stdout if stderr contained warnings or other messages. The updated implementation now captures stdout and stderr into distinct buffers, returning only the stdout content for parsing while still displaying both streams to the terminal. If the command fails, the stderr content is now included in the returned error message. Corresponding test cases have been updated, and a new test TestRunAnyscaleCLI_StderrNotInOutput was added to verify that stderr content does not interfere with the returned stdout.

[sai-miduthuri]

Everything else looks good except for the handling of stdout and stderr in the case of err != nil.