"--filter" doesn't use shebang in executable filters

[jkr]

Presumably as a result of 3fe6b57, pandoc now prefers the default version of program to that in the shebang. For example, in arch, python means python3, so I put #!/usr/bin/env python2 at the top of my executable. But if invoked with --filter, it still runs python.

Example, let's call it "filter.py":

#!/usr/bin/env python2

import pandocfilters as PF
import sys

def str_to_py_version(k, v, fmt, meta):
    if k == "Str":
        return PF.Str(sys.version.split()[0])

if __name__ == '__main__':
    PF.toJSONFilter(str_to_py_version)

using development pandoc:

jkr@bucket $ echo "foo" | pandoc -t json | ./filter.py | pandoc -f json
<p>2.7.6</p>

jkr@bucket $ echo "foo" | pandoc --filter ./filter.py
<p>3.4.0</p>

It should use the shebang in executables.

[jkr]

A quick look at the code suggests that it's because findExecutable (on line 101) only looks in the PATH for executables, and if it doesn't find them there, assumes they're not executable.

[jgm]

Yep - we should also check directly to see if the file is executable.

+++ Jesse Rosenthal [Jun 30 14 12:11 ]:

A quick look at the code suggests that it's because findExecutable (on
line 101) only looks in the PATH for executables, and if it doesn't
find them there, assumes they're not executable.

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References

1. "--filter" doesn't use shebang in executable filters #1389 (comment)

[jkr]

Actually, findExecutable seems like it would do the job, if given in an absolute path. Would there be any problem with running canonicalizePath if it's a path? Something like

mbexe <- if '/' `elem` f -- don't check PATH if filter name it has a path
                  then canonicalizePath f >>= findExecutable
                  else findExecutable f

Seems to build and work.