shfmt should repair tab indented here docs.

[docwhat]

From the bash man page:

If the redirection operator is <<-, then all leading tab characters are stripped from input lines and the line containing delimiter. This allows here-documents within shell scripts to be indented in a natural fashion.

Given this:

# spaces not tab.
fun() {
    cat <<-DOC
        some important text
    DOC
}

... I would like shfmt to repair this... because a lot of editors have a hard time with this if you're using spaces for indentation overall.

[mvdan]

Can you clarify what you mean by "repair"? Perhaps give me an input file and how you run shfmt on it, and what you expect the output to be.

[docwhat]

Given

# spaces not tab.
fun() {
    cat <<-DOC
        some important text
    DOC
}

for i in {1..10}; do
    echo "run $i"
    fun
done

When you run:

shfmt -i 4 -s script-with-spaces.bash   

I would expect:

# spaces not tab.
fun() {
    cat <<-DOC
      some important text
    DOC
}

for i in {1..10}; do
    echo "run $i"
    fun
done

But I get:

/tmp/foo.bash:3:9: unclosed here-document 'DOC'

Basically, shfmt would detect that DOC isn't closed and try to repair it by replacing the first n spaces with a tab. n would be calculated by looking at the stop line.

[mvdan]

Basically, shfmt would detect that DOC isn't closed and try to repair it by replacing the first n spaces with a tab. n would be calculated by looking at the stop line.

Hmm. shfmt is just a formatter, though - if its input is invalid Bash, it generally shouldn't try to fix it automatically. In other words, the parser should error if the input is invalid. We don't have a middle ground where we may return warnings or fix the program for the user. See https://github.com/mvdan/sh/issues/765 as another example, for instance.

I think your suggestion falls under the kind of tool to spot bugs or auto-fix common shell mistakes. You could certainly build a tool like that on top of our Go syntax package. For instance, if that tool runs the parser and encounters /tmp/foo.bash:3:9: unclosed here-document 'DOC', it could look at the following lines to see if one could be the closing heredoc line by replacing leading spaces with tabs.

[mvdan]

I'm going to close this as per the last comment. If someone wants to coordinate writing such a "fix common mistakes" tool, please feel free to open an umbrella issue or discussion on this repository, like https://github.com/mvdan/sh/issues/730. Thanks!