Feature Request: Provide an option to specify the fallback shell type

[moonfruit]

For new checks and feature suggestions

• [x] https://www.shellcheck.net/ (i.e. the latest commit) currently gives no useful warnings about this
• [x] I searched through https://github.com/koalaman/shellcheck/issues and didn't find anything related

Description

Some tools like bash-language-server detect the shell type themselves and add the option --shell=SHELLNAME to shellcheck. But this option will overwrite shellcheck directive for type in file or .shellcheckrc.

I think a new option should be provided to specify a fallback shell type.

[brother]

Not sure this is a shellcheck problem really.

Would it be possible to add the shell directive at the top of the file?

brother ~$ cat /tmp/test.sh 
#!/bin/sh

myvar=(1 2 3)

echo "${myvar[1]}"
brother ~$ shellcheck --norc /tmp/test.sh 

In /tmp/test.sh line 3:
myvar=(1 2 3)
      ^-----^ SC3030 (warning): In POSIX sh, arrays are undefined.

In /tmp/test.sh line 5:
echo "${myvar[1]}"
      ^---------^ SC3054 (warning): In POSIX sh, array references are undefined.

For more information:
  https://www.shellcheck.net/wiki/SC3030 -- In POSIX sh, arrays are undefined.
  https://www.shellcheck.net/wiki/SC3054 -- In POSIX sh, array references are...
brother ~$ shellcheck --norc --shell=bash /tmp/test.sh 
brother ~$ cat /tmp/test.sh 
#!/bin/sh
# shellcheck shell=bash

myvar=(1 2 3)

echo "${myvar[1]}"
brother ~$ shellcheck --norc --shell=bash /tmp/test.sh 
brother ~$ shellcheck --norc /tmp/test.sh 

[moonfruit]

For example:

test.sh:

#!/bin/sh
# shellcheck shell=bash
echo -e "abc"

And check with shellcheck

$ shellcheck test.sh
$ shellcheck --shell=sh test.sh

In test.sh line 3:
echo -e "abc"
     ^-- SC3037 (warning): In POSIX sh, echo flags are undefined.

For more information:
  https://www.shellcheck.net/wiki/SC3037 -- In POSIX sh, echo flags are undef...

You can find that the command line option override the shell directive defined in the file.

[moonfruit]

bash-language-server always sets --shell= to what it thinks the shell is. I think it should set it to a fallback shell type to allow # shellcheck shell=bash to work. But shellcheck does not have this function.

[brother]

maybe that should stop doing such things then?

[moonfruit]

Well, now that you've said that, all I can do now is post this question to bash-language-server.

[moonfruit]

It seems to me that a small change on both sides would be the feature that still works. Otherwise, an external tool may be needed to parse the shellcheck directive to solve the problem more perfectly.

[brother]

I don't think this need to get all crazy but it looks like bash-lang-server is (lack of words) abusing the shell directive. We developers and and end consumers can set those options ourselves if needed.

[ale5000-git]

@moonfruit My opinion: shellcheck already detect the shell by itself in multiple ways so there isn't any need for the server to suggest it (even more so if the suggestions are wrong).

[moonfruit]

I'm not the maintainer of bash-language-server, I can't decide what it will do. I just made a suggestion.