tools/gstreamer-completion: Bash 3.2 compatibility fixes

Compatible with bash 3.2; doesn't require the bash-completion package at
all (though the easiest way to install this script is still to install
bash-completion, and then drop this script into /etc/bash_completion.d).

Note that bash 3 doesn't break COMP_WORDS according to characters in
COMP_WORDBREAKS, so "property=val" looks like a single word, so this
won't complete property values (on bash 3). Similarly,
"--gst-debug-level=<TAB>" won't complete properly (on bash 3), but
"--gst-debug-level <TAB>" will.

For that reason, I now offer "--gst-debug-level" etc as completions
instead of "--gst-debug-level=".

Functions "_init_completion" and "_parse_help" were provided by the
bash-completion package >= 2.0; now I roll my own equivalent of
"_parse_help", and instead of "_init_completion" I use
"_get_comp_words_by_ref" which is available from bash-completion 1.2
onwards. If the bash-completion package isn't available at all I use
bash's raw facilities, at the expense of not completing properly when
the cursor is in the middle of a word.

The builtin "compopt" doesn't exist in bash 3; those users will just
have to live with the inconvenience of "property=" completing to
"property= " with a trailing space. Property values aren't completed
properly anyway on bash 3 (see above).

"[[ -v var ]]" to test whether a variable is set, also doesn't exist in
bash 3. Neither does ";;&" to fall through in a "case" statement.

In the unit tests:

* On my system (OS X), "#!/bin/bash" is bash 3.2, whereas
  "#!/usr/bin/env bash" is the 4.2 version I built myself.
* I have to initialise array variables like "expected=()", or bash 3
  treats "+=" as appending to an array already populated with one empty
  string.

1 files changed, 36 insertions, 13 deletions

diff --git a/tools/gstreamer-completion b/tools/gstreamer-completion
index 4489f7dac..b262b301d 100644
--- a/tools/gstreamer-completion
+++ b/tools/gstreamer-completion
@@ -4,12 +4,14 @@
 _gst_version=1.0
 
 _gst_inspect() {
-    local cur prev words cword split
-    _init_completion -n : -s || return
+    local cur cword prev words
+    _gst_init_completion
+    [[ "$cur" == "=" ]] && cur=
+
     _gst_common_options || return
 
     COMPREPLY=( $(compgen \
-        -W "$(_parse_help gst-inspect-$_gst_version --help-all) \
+        -W "$(_gst_parse_help gst-inspect-$_gst_version) \
             $(_gst_plugins) $(_gst_elements)" \
         -- "$cur") )
     [[ $COMPREPLY == *= ]] && compopt -o nospace 2>/dev/null
@@ -18,8 +20,7 @@ complete -F _gst_inspect gst-inspect-$_gst_version
 
 _gst_launch() {
     local cur cword prev words
-    _init_completion -n : || return
-
+    _gst_init_completion
     local curtype option element property
     _gst_launch_parse
     _gst_common_options || return
@@ -30,7 +31,7 @@ _gst_launch() {
 complete -o default -F _gst_launch gst-launch-$_gst_version
 
 _gst_common_options() {
-    if [[ -v curtype && -v option ]]; then  # Called from _gst_launch
+    if [[ -n "$curtype" ]]; then  # Called from _gst_launch
         [[ $curtype == optionval ]] || return 0
     else  # Called from _gst_inspect
         local option="$prev"
@@ -52,13 +53,17 @@ _gst_common_options() {
 
 _gst_launch_compgen() {
     case $curtype in
-        option|option-or-element)
+        option)
             compgen \
-                -W "$(_parse_help gst-launch-$_gst_version --help-all)" \
-                -- "$cur"
-            ;;&  # test next pattern too.
-        element|option-or-element)
+                -W "$(_gst_parse_help gst-launch-$_gst_version)" \
+                -- "$cur" ;;
+        element)
             compgen -W "$(_gst_elements)" -- "$cur" ;;
+        option-or-element)
+            compgen \
+                -W "$(_gst_parse_help gst-launch-$_gst_version) \
+                    $(_gst_elements)" \
+                -- "$cur" ;;
         optionval)
             case "$option" in
                 -o|--output) compgen -f -- "$cur" ;;
@@ -120,8 +125,7 @@ _gst_property_values() {
 # ($cur is the word currently being completed.)
 #
 # Before calling this function make sure that $curtype, $option, $element and
-# $property are local, and that $cur, $cword and $words have been initialised
-# by calling _init_completion.
+# $property are local, and that $cur, $cword and $words have been initialised.
 #
 # See test cases in tests/misc/test-gstreamer-completion.sh in the
 # gstreamer source repository.
@@ -161,3 +165,22 @@ _gst_takes_arg() {
         *) false;;
     esac
 }
+
+_gst_parse_help() {
+    $1 --help-all 2>&1 | grep -Eo -e '--[a-z-]+'
+}
+
+_gst_init_completion() {
+    if type _get_comp_words_by_ref &>/dev/null; then
+        # Available since bash-completion 1.2
+        _get_comp_words_by_ref cur cword prev words
+    else
+        # bash-completion not installed or too old. Use bash's raw facilities.
+        # This won't complete properly if the cursor is in the middle of a
+        # word.
+        cur="${COMP_WORDS[COMP_CWORD]}"
+        prev="${COMP_WORDS[COMP_CWORD-1]}"
+        cword=$COMP_CWORD
+        words=("${COMP_WORDS[@]}")
+    fi
+}