syntax error near unexpected token `(' (possible bash bug)

Question

Maybe I've just triggered an error in bash's parser, but before filing a bugreport I wan't to ask anyways, maybe I'm just getting blind and it's not a bash bug after all ...

This is the script (ok, stripped down version of the actual one):

$ cat bash-parse-error.1.sh
#! /bin/sh

echo "$(
    if false
    then
            exit 0
    fi

    # echo "("
    case FOO in
            FOO)
                    echo "("
                    ;;
    esac
)"
$ ./bash-parse-error.1.sh
./bash-parse-error.1.sh: line 12: syntax error near unexpected token `('
./bash-parse-error.1.sh: line 12: `                 echo "("'

Now, If I de-comment the extra echo command, the script works as you would expect, printing two opening parenthesises:

$ cat bash-parse-error.2.sh
#! /bin/sh

echo "$(
    if false
    then
            exit 0
    fi

    echo "("
    case FOO in
            FOO)
                    echo "("
                    ;;
    esac
)"
$ ./bash-parse-error.2.sh
(
(

Alternatively, removing the if-false-then-exit block (doing whatever I want with the commented out echo command) will make the error go away as well:

$ cat bash-parse-error.3.sh
#! /bin/sh

echo "$(
    case FOO in
            FOO)
                    echo "("
                    ;;
    esac
)"
$ ./bash-parse-error.3.sh
(

So, is it me or is it bash?

/edit: a) no workaround needed, already got one, thx anyways

b) #! /usr/bash obviously exhibits same problem, because

c) versions tested: 4.3.33(1) and 4.3.39(1)

Answer 1

What version of bash are you seeing this with? (I see it with 3.2.25(1)-release but not with 4.1.2(1)-release or 4.3.42(1)-release.)

Using the optional ( on the case statement works around the problem as well.

An issue about this was filed for shellcheck as https://github.com/koalaman/shellcheck/issues/482 which references the Command Substitution Bash Hackers Wiki page which discusses it too (as a "Construct to avoid").

Though technically that issue is with a closing ) not an opening one as you've found here.

bash 4.2.46(1)-release from CentOS 7 fails on .1.sh but works on the other two. And adding the ( fixes .1.sh there as well.