syntax: add bats support

[kolyshkin]

Bats (https://github.com/bats-core/bats-core/) is a tool to write scripts in bash, with a few twists. A .bats file looks very much like a shell file, except for some added functions and features.

I think, the only change that is absolutely required to support bats is to recognise @test statement.

@test "some name" { denotes a test case. From the purpose of a formatter, I think it can be treated similar to function some_name {.

For the reference, shellcheck has added .bats support here: damienrg/shellcheck@f187382

[mvdan]

It's unfortunate that Bats isn't compatible with POSIX Shell; I imagine they could have done something similar to what Go did, like:

function TestFooBar {
    [...]
}

But in any case, that ship has sailed. They created their own language, and I clearly can't resist that or the tool's popularity.

At least they stuck to Bash and only made that one language change. I think we could add another shell language variant based off of Bash, and teach the parser about an extra reserved word.

[mvdan]

Annoyingly enough, upstream bats allows this:

@test foo bar { body; }

@test "foo bar" "baz" { body; }

That is, it supports multiple words as the test description, not just one. I don't think anyone actually does that, and they don't have a formal language specification other than the somewhat horrifying regular expression below, so I'll go ahead and do the same thing shellcheck does - only support the @test WORD { COMMANDS; } form.

export BATS_TEST_PATTERN="^[[:blank:]]*@test[[:blank:]]+(.*[^[:blank:]])[[:blank:]]+\{(.*)\$"

[kolyshkin]

In addition to the above comment, bats convert those test names to valid bash function names, e.g.

• @test foo bar { becomes test_foo_bar() {
• @test "foo bar" "baz" { -> test_foo_bar-22_-22baz() {

The internal test name is available at ${BATS_TEST_NAME}.

The test name encoding is done here: https://github.com/bats-core/bats-core/blob/master/libexec/bats-core/bats-preprocess#L4

[mvdan]

I imagine that doesn't really concern us, because we never have to build the test name. I still find it bizarre that they allow multiple words in that syntax.

[mvdan]

This is now in master; please test it and let me know how it works. Note that using something like shfmt -w . to walk directories will not find *.bats files just yet; that's a bit that I'm still working on.

[kolyshkin]

@mvdan thanks so much for implementing this!

I just compiled shfmt from the current HEAD (which happens to be c5ff78f) and it shows nothing for bats files.

For example

$ cat << EOF > a.bats
> @test "one two" {
>   echo  foo
>  }
> EOF
$ ./shfmt -ln bats -d a.bats; echo $? 
0
$ ./shfmt -ln bats a.bats; echo $? 
0

Just in case, I checked the same binary works with bash input. Not sure if I'm missing something...

[mvdan]

Oh dear, this is why unit tests aren't always enough :)

[mvdan]

Okay, that was a silly regression introduced in a "cleanup" done around the same time, but unrelated to Bats support. I've added copious tests, so that won't happen again. Please try again.

[kolyshkin]

aaand it works now, thanks! 🤗