Continuous Integration Support

[ratsclub]

Hello,

I would like to run smlfmt on CI to check if the files are formatted correctly. I tried to run all the command-line flags and couldn't find one that would return an error code in case of a file not being formatted. Is there some way to setup something like this?

Thanks for the awesome tool!

[shwestrick]

Yes, that should be easy to set up! Although, smlfmt should already exit with a nonzero return code when it fails.

Could you show me the command you tried and what return code you got?

[shwestrick]

Oh wait, or maybe you're looking for a mode to check if a file has previously already been formatted by smlfmt?

[ratsclub]

Could you show me the command you tried and what return code you got?

• smlfmt --preview-only src/railroad.sml: doesn't exit with a nonzero return code.
• smlfmt src/railroad.sml: asks for [y/N], I don't think I can use it on CI

[shwestrick]

Hmm sorry, I'm still confused about what you're asking for.

It looks like you're trying to reformat src/railroad.sml and check whether or not it succeeds (e.g., check if there is an SML syntax error). If smlfmt --preview-only src/railroad.sml doesn't exit with nonzero return, then it succeeded.

Maybe you're trying to do something else? Are you trying to check if src/railroad.sml has already been formatted in the past? One way of doing this would be to run smlfmt on it again, and see if the result is different:

$ cat src/railroad.sml | smlfmt --stdio | diff src/railroad.sml -

This command has returncode 0 if src/railroad.sml has already previously been formatted, and returncode 1 otherwise.

[ratsclub]

Oh, yes! This is exactly what I wanted, I'm sorry if I was not clear enough. The idea would be to feed smlfmt my *.mlb file and have it return an error code if the code is not formatted. Do you know if I can do something like this?

[shwestrick]

Ah I see! I don't think it would be too difficult to implement, but realistically I probably won't have time to get to it right away.

Any chance you're interested in giving it a shot? I'd be happy to review a PR.

Here's some thoughts:

• We would need to add a new command-line flag to smlfmt. Not sure what a good name would be; open to suggestions.
• I think we would only need to modify formatOneSML.
  • When you pass a .mlb, it ultimately calls this function on every .sml file.
• Idea would be: if the flag is turned on, run the formatter as normal, and then check if there is a difference between the new formatted code and the original contents of the file.
  • If there is a difference, then exit early with an error.
  • If no difference, then silently continue (i.e., don't do anything else for this .sml file)
  • This would find the first "offending" file. Alternatively, it wouldn't be too difficult to accumulate a list of offending files and print them all out.