Fix tilde (~) completion with _filedir

This fixes tilde completion when doing for instance `ls ~<TAB>'.  See
also: Alioth #312613.

Added _tilde() helper function.

Contrary to _expand() and __expand_tilde_by_ref(), _tilde() also leaves the
tilde (~) intact.  Replacement of the tilde has been a complaint in other
bugreports, especially since plain bash completion (without bash-completion
installed) doesn't expand the tilde when doing a `ls ~<TAB>'.

To run the tests:

    ./run completion/ls.exp
    ./run unit/_tilde.exp

CHANGES

@@ -10,6 +10,9 @@ bash-completion (2.x)
   * Add "short" tarball extensions to unxz, unlzma etc completions.
   * Improve /etc/init.d/* and sqlite3 completions.
 
+  [ Freddy Vulto ]
+  * Added _tilde(), fix ~username completion (Alioth: #312613, Debian: #587095)
+
  -- David Paleino <d.paleino@gmail.com>  Wed, 16 Jun 2010 17:53:22 +0200
 
 bash-completion (1.2)

bash_completion

@@ -618,7 +618,7 @@ _filedir()
 {
     local i IFS=$'\t\n' xspec
 
-    __expand_tilde_by_ref cur
+    _tilde "$cur" || return 0
 
     local -a toks
     local quoted tmp
@@ -803,7 +803,26 @@ _available_interfaces()
 }
 
 
+# Perform tilde (~) completion
+# @return  True (0) if completion needs further processing, 
+#          False (> 0) if tilde is followed by a valid username, completions
+#          are put in COMPREPLY and no further processing is necessary.
+_tilde() {
+    local result=0
+    # Does $1 start with tilde (~) and doesn't contain slash (/)?
+    if [[ ${1:0:1} == "~" && $1 == ${1//\/} ]]; then
+        # Try generate username completions
+        COMPREPLY=( $( compgen -P '~' -u "${1#\~}" ) )
+        result=${#COMPREPLY[@]}
+    fi
+    return $result
+}
+
+
 # Expand variable starting with tilde (~)
+# We want to expand ~foo/... to /home/foo/... to avoid problems when
+# word-to-complete starting with a tilde is fed to commands and ending up
+# quoted instead of expanded.
 # Only the first portion of the variable from the tilde up to the first slash
 # (~../) is expanded.  The remainder of the variable, containing for example
 # a dollar sign variable ($) or asterisk (*) is not expanded.
@@ -832,7 +851,7 @@ __expand_tilde_by_ref() {
             #    becomes "~a".  Double quotes allow eval.
             # 2: Remove * before the first slash (/), i.e. "~a/b"
             #    becomes "b".  Single quotes prevent eval.
-            #                          +-----1----+ +---2----+
+            #       +-----1----+ +---2----+
             eval $1="${!1/%\/*}"/'${!1#*/}'
         else 
             # No, $1 doesn't contain slash

test/lib/completions/ls.exp

@@ -19,4 +19,14 @@ if {[assert_exec {ls --help} "" "" "unsupported"]} {
 sync_after_int
 
 
+set test "~part should complete to ~full"
+assert_bash_exec {compgen -u} {} /@ users
+find_unique_completion_pair $users part full
+set cmd [format {ls ~%s} $part]
+assert_complete "~$full/" $cmd $test
+
+
+sync_after_int
+
+
 teardown

test/unit/_tilde.exp

@@ -0,0 +1,51 @@
+# @param string $part  Reference to variable to hold partial unique username
+# @param string $full  Reference to variable to hold full unique username
+proc setup {part full} {
+    upvar $part _part
+    upvar $full _full
+
+    assert_bash_exec {compgen -u} {} /@ users
+    find_unique_completion_pair $users _part _full
+    save_env
+}
+
+
+proc teardown {} {
+    assert_env_unmodified {
+        /COMPREPLY=/d
+    }
+}
+
+
+setup part full
+
+
+set test "function should run without errors"
+assert_bash_exec {_tilde > /dev/null} $test
+
+
+sync_after_int
+
+
+set test "function should not pollute environment"
+# NOTE: A possible environment pollution is detected by assert_env_modified() in teardown()
+assert_bash_exec {foo() { local aa="~"; _tilde "$aa"; }; foo; unset foo} $test
+
+
+sync_after_int
+
+
+set test "~full should complete to ~full unmodified"
+set cmd [format {_tilde "~%s"; printf "%%s" "${COMPREPLY[@]}"} $full]
+assert_bash_list "~$full" $cmd $test
+
+
+sync_after_int
+
+
+set test "~part should complete to ~full"
+set cmd [format {_tilde "~%s"; printf "%%s" "${COMPREPLY[@]}"} $part]
+assert_bash_list "~$full" $cmd $test
+
+
+teardown