fix(_comp_array_filter): support consistent anchoring also for -E

bash_completion

@@ -257,17 +257,19 @@ _upvars()
 #
 # Options:
 #     -E          $2 is interpreted as a POSIX extended regular expression.
-#                 This is always the partial matching unless ^, $ is included
-#                 in $2.
-#     -F          $2 is interpreted as a fixed string.
-#     -G          $2 is interpreted as a glob pattern.
-#
-#     -p          Combined with -F or -G, it performs the prefix matching.
-#     -s          Combined with -F or -G, it performs the suffix matching.
-#     -m          Combined with -F or -G, it performs the middle matching.
+#                 The default anchoring is `-m` (see below).
+#     -F          $2 is interpreted as a fixed string.  The default anchoring
+#                 is `-m` (see below).
+#     -G          $2 is interpreted as a glob pattern.  The default anchoring
+#                 is `-x` (see below).
+#
+#     -p          Combined with -EFG, it performs the prefix matching.
+#     -s          Combined with -EFG, it performs the suffix matching.
+#     -m          Combined with -EFG, it performs the middle matching.
+#     -x          Combined with -EFG, it performs the exact matching.
+#
 #     -r          Revert the condition, i.e., remove elements that satisfy
 #                 the original condition.
-#
 #     -C          Array compaction is not performed.
 #
 # @return 2 with a wrong usage, 1 when any elements are removed, 0 when the set
@@ -278,14 +280,14 @@ _comp_array_filter()
 {
     local _comp_local_flags='' _comp_local_pattype='' _comp_local_anchoring=''
     local OPTIND=1 OPTARG='' OPTERR=0 _comp_local_opt=''
-    while getopts 'EFGpsmrC' _comp_local_opt "$@"; do
+    while getopts 'EFGpsmxrC' _comp_local_opt "$@"; do
         case $_comp_local_opt in
             [EFG]) _comp_local_pattype=$_comp_local_opt ;;
-            [psm]) _comp_local_anchoring=$_comp_local_opt ;;
+            [psmx]) _comp_local_anchoring=$_comp_local_opt ;;
             [rC]) _comp_local_flags=$_comp_local_opt$_comp_local_flags ;;
             *)
                 printf 'bash_completion: %s: %s\n' "$FUNCNAME" 'usage error' >&2
-                printf 'usage: %s %s\n' "$FUNCNAME" "[-EFGpsmrC] ARRAY_NAME CONDITION" >&2
+                printf 'usage: %s %s\n' "$FUNCNAME" "[-EFGpsmxrC] ARRAY_NAME CONDITION" >&2
                 return 2
                 ;;
         esac
@@ -294,7 +296,7 @@ _comp_array_filter()
     shift $((OPTIND - 1))
     if (($# != 2)); then
         printf 'bash_completion: %s: %s\n' "$FUNCNAME" "unexpected number of arguments: $#" >&2
-        printf 'usage: %s %s\n' "$FUNCNAME" "[-EFGpsmrC] ARRAY_NAME CONDITION" >&2
+        printf 'usage: %s %s\n' "$FUNCNAME" "[-EFGpsmxrC] ARRAY_NAME CONDITION" >&2
         return 2
     elif [[ $1 != [a-zA-Z_]*([a-zA-Z_0-9]) ]]; then
         printf 'bash_completion: %s: %s\n' "$FUNCNAME" "invalid array name '$1'." >&2
@@ -312,14 +314,19 @@ _comp_array_filter()
     local _comp_local_predicate='' _comp_local_pattern=$2
     case $_comp_local_pattype in
         E)
-            _comp_local_predicate='[[ $_comp_local_value =~ $_comp_local_pattern ]]'
+            case $_comp_local_anchoring in
+                p) _comp_local_predicate='[[ $_comp_local_value =~ ^($_comp_local_pattern) ]]' ;;
+                s) _comp_local_predicate='[[ $_comp_local_value =~ ($_comp_local_pattern)$ ]]' ;;
+                x) _comp_local_predicate='[[ $_comp_local_value =~ ^($_comp_local_pattern)$ ]]' ;;
+                *) _comp_local_predicate='[[ $_comp_local_value =~ $_comp_local_pattern ]]' ;;
+            esac
             ;;
         F)
             case $_comp_local_anchoring in
                 p) _comp_local_predicate='[[ $_comp_local_value == "$_comp_local_pattern"* ]]' ;;
                 s) _comp_local_predicate='[[ $_comp_local_value == *"$_comp_local_pattern" ]]' ;;
-                m) _comp_local_predicate='[[ $_comp_local_value == *"$_comp_local_pattern"* ]]' ;;
-                *) _comp_local_predicate='[[ $_comp_local_value == "$_comp_local_pattern" ]]' ;;
+                x) _comp_local_predicate='[[ $_comp_local_value == "$_comp_local_pattern" ]]' ;;
+                *) _comp_local_predicate='[[ $_comp_local_value == *"$_comp_local_pattern"* ]]' ;;
             esac
             ;;
         G)