Ability to run in checking mode

[Kernald]

It would be nice to be able to run textpbfmt on files in CI to check that they're properly formatted. google-java-format exposes this use-case through two options for example:

  --dry-run, -n
    Prints the paths of the files whose contents would change if the formatter were run normally.
  --set-exit-if-changed
    Return exit code 1 if there are any formatting changes.

[kssilveira]

hi, I agree.

One workaround would be to write the output to a different file and then do a diff.

[dougthor42]

Another option is to wrap it in a light shell script that captures the stdout of -dry_run and exits 1 if there's any content:

TXTPBFMT_ARGS=()
if [[ "${1:-}" == "check" ]]; then
    TXTPBFMT_ARGS+=("-dry_run")
fi
readonly TXTPBFMT_ARGS

# Note: git does not have a long-form of -z. It means null-terminate results
output="$(
    "${GIT_BIN}" \
        ls-files \
        -z \
        "*.textproto" "*.txtpb" "*.txtproto" ".textpb" |
        xargs --null --no-run-if-empty "${TXTPBFMT_BIN}" "${TXTPBFMT_ARGS[@]}"
)"
# Note: txtpbfmt always has a 0 exit code if it runs successfully, whether
# or not it had to format anything.
# However, -dry_run will print to stdout if changes would be made. It will
# not print anything if things are already well formatted.
if [[ "${1:-}" == "check" && -n "${output}" ]]; then
    echo "Some files would be modified by txtpbfmt."
    echo "Please run 'bazel run //tools/dev:txtpbfmt' to format them."
    exit 1
fi

[kssilveira]

thanks, I'm happy to review if someone wants to add something like the suggested --set-exit-if-changed to make this integration easier.