[bash-completion] Fix tab separation on macOS

[benlangmuir]

Summary

We have a regex that needs to match a tab character in the command output, but on macOS sed doesn't support '\t', causing it to split on the 't' character instead. Some options:

• use perl -p -e 's/\t.*//', which does handle '\t'
• put a literal tab character in the string passed to sed
• use sed -e $'s/\t.*//', which will cause bash to expand the '\t' before passing it to sed

[ruiu]

Even though Perl may be installed to 99.99% of machines that use this autocomplete script, using perl instead of sed is too much. If we could use perl, we'd have wrote this script entirely in perl in the first place. We shouldn't add a dependency to perl.

I wonder if you could replace \t with \0x09. At least it works on my machine which has GNU sed.

[benlangmuir]

In D47273#1109934, @ruiu wrote:

I wonder if you could replace \t with \0x09. At least it works on my machine which has GNU sed.

Unfortunately that doesn't work either on mac :-\

EDIT: nor does \x9, which I think is what you meant? Or maybe gnu sed support \0x as well as \x?

[ruiu]

How about

sed -e "$(echo -e 's/\t.*//')"

?

[benlangmuir]

In D47273#1109985, @ruiu wrote:

sed -e "$(echo -e 's/\t.*//')"

Yep, that works! Is there a reason you prefer that over the more succinct $'s/\t.*//'?

[ruiu]

Oh, I didn't know the existence of $''. Thank you for the suggestion! I wonder which version of bash started supporting that notation. Do you know if all recent versions of bash support it? Unfortunately $'' bash is very hard query to google...

[ruiu]

Looks like $'' is there since bash 2.0 which should be pretty safe to use in the script. So feel free to use $'' instead of $(echo ...) in this patch.

[ruiu]

(I found that information at http://wiki.bash-hackers.org/scripting/bashchanges#quoting_expansions_substitutions_and_related)

[benlangmuir]

Thanks for looking up the supported bash version! Updated diff.

[ruiu]

LGTM

[yamaguchi]

LGTM

[benlangmuir]

r333202

utils/bash-autocomplete.sh

       arg="$arg${COMP_WORDS[$i]}"
     else
       arg="$arg${COMP_WORDS[$i]},"
     fi
   done
 
   # expand ~ to $HOME
   eval local path=${COMP_WORDS[0]}
-  flags=$( "$path" --autocomplete="$arg" 2>/dev/null | sed -e 's/\t.*//' )
+  # Use $'\t' so that bash expands the \t for older versions of sed.
+  flags=$( "$path" --autocomplete="$arg" 2>/dev/null | sed -e $'s/\t.*//' )
   # If clang is old that it does not support --autocomplete,
   # fall back to the filename completion.
   if [[ "$?" != 0 ]]; then
     _clang_filedir
     return
   fi
 
   # When clang does not emit any possible autocompletion, or user pushed tab after " ",