Support sequence of formatters

[zimbatm]

In some cases, developers might want to run a sequence of formatters for the same file type. For example, re-order the import headers with one tool, and then use the main code formatted to fix the output of the first tool.

[zimbatm]

What happens is that some developers want to:

1. Format the file imports in the file header with one tool
2. Then run the normal formatter to fix the output of the first tool and make sure that the rest of the file is also properly formatted.

In order to support that, we need to find a way to apply these tools in sequence.

Maybe a config format change would be:

[formatter.ormolu]
pre_command = "import-fixer"
command = "ormolu"
after = "haskell-header"
includes = ["*.hs"]

[blaggacao]

I think the usage of sh is also a fair game, so that would mean nothing to do:

[formatter.beancount]
command = "sh"
options = [
  "-c",
  "for f in $@; do bean-format $f; done",
]
includes = ["*.beancount"]

Maybe a slightly friendlier sh interface might be a good & cheap option?

[formatter.beancount]
script = """
for f in $@; do bean-format $f; done
"""
includes = ["*.beancount"]

But I probably miss some aspects...

[zimbatm]

That's a good idea.

If there is tool A and B, we want to encourage calling A "$@" && B "$@" over for f in "#@"; do A "$f" && B "$f"; done. I learned that with terraform fmt that only supports one file at a time. The latter is easily one or two order of magnitude slower.

[blaggacao]

Do you mean to implement a requires_singleton_file = true (or similar arg) ?

[zimbatm]

I meant that the example for sequencial calls should avoid using a for loop.

Overall, I would rather fix upstream formatters than add more config options :)

[blaggacao]

Might this issue be even solvable via documentation, clarifying the use of sh or is there a need for more individual error reporting on which of the sequence of commands has failed?

[zimbatm]

Of course, Documentation over existing best practices is always a good first step.

[fbergroth]

Hi, I just installed this (0.3.0), and I tried the following

[formatter.python]
command = "sh"
options = [
  "-c",
  """
  isort "$@" && black "$@"
  """,
]
includes = ["*.py"]

but was wondering why my python file wasn't formatted.

Turns out that the first file is passed as $0, but $@ is from $1 and onwards. Notice xx is missing from output.

$ sh -c 'echo AA $@ BB' xx yy zz
AA yy zz BB

I fixed this by adding a dummy argument:

[formatter.python]
command = "sh"
options = [
  "-c",
  """
  isort "$@" && black "$@"
  """,
  "dummy",
]
includes = ["*.py"]

Does this not happen for you?

Edit: isort --overwrite-in-place "$@" seems to be required for --stdin to work.

[zimbatm]

Good catch. f440332 includes your fix, and replaces dummy with --. -- is generally a convention in tools to say that the next arguments will be passed along to a sub-program.

[fbergroth]

Cool. It's easy to miss, so something friendlier would be nice, as suggested above.

Perhaps

sh = "..."

can desugar to

command = "/bin/sh"
options = ["-euc", "...", "--"]

[yajo]

I think it would be easier for the devs to just have a priority option. All hooks with same priority should run in parallel. Then, the same with next priority. Default priority could be 0. Example:

[formatter.isort]
command = "isort"
includes = ["*.py"]

[formatter.black]
command = "black"
priority = 1 # Runs after all formatters with priority 0 (default)
includes = ["*.py"]