`--check` option to merely check that `--inplace` would be a no-op

[gasche]

I would like to ask ocp-indent: is my file (or the range specified etc.) correctly indented?

[js-guest]

This is a feature we'd like at Jane Street as well! On Oct 29, 2015 3:38 AM, "Gabriel Scherer" notifications@github.com wrote:

I would like to ask ocp-indent: is my file (or the range specified etc.) correctly indented?

— Reply to this email directly or view it on GitHub https://github.com/OCamlPro/ocp-indent/issues/196.

[AltGr]

Ok, wouldn't be too difficult. In the meantime, you can use diff -q FILE <(ocp-indent FILE)

[gasche]

I wonder what the output should be of --check should be. I have two use-cases in mind:

• inside some kind of shell script (or for general programmability), a return value would be convenient (for example following the UNIX convention of returning 0 when it works, and some error code when --check fails)
• my main use-case would be something like ocp-indent --check **/*.ml*, or find . -name '*.ml*' | xargs ocp-indent --check, to know whether all the OCaml source files around me are correctly indented. Then I would expect a greppable textual output, for example something like "ocp-indent --check %S: %s" filename (if ok then "pass" else "fail"). Another (better?) option would be to print nothing when the file is correct, and print failure message(s) when it is incorrect; I think users would easily understand this convention, and it is convenient for multi-file processing.
• people may want to use this check in a git commit hook, but I have no experience with this so I don't know what kind of interface would be convenient (I suppose return values are fine).

My preference would be to have:

• no output if --check is correct, and a 0 return code
• an error message (on stdout or stderr) if --check finds a discrepancy, and a non-0 return code

[vogler]

people may want to use this check in a git commit hook, but I have no experience with this so I don't know what kind of interface would be convenient (I suppose return values are fine).

I'm using it like this: https://github.com/goblint/analyzer/blob/master/scripts/hooks/pre-commit#L52