main: check for partial paths separately

It's really annoying to have partial paths appear the same as paths to
complete files. However, it is still nice to be able to highlight them.
Full paths are now bold while partial paths use plain underline.

docs/highlighters/main.md

@@ -29,6 +29,7 @@ This highlighter defines the following styles:
 * `hashed-command` - hashed commands
 * `autodirectory` - a directory name in command position when the `AUTO_CD` option is set
 * `path` - existing filenames
+* `partial-path` - partial paths (prefixes of existing files)
 * `path_pathseparator` - path separators in filenames (`/`); if unset, `path` is used (default)
 * `path_prefix` - prefixes of existing filenames
 * `path_prefix_pathseparator` - path separators in prefixes of existing filenames (`/`); if unset, `path_prefix` is used (default)

highlighters/main/main-highlighter.zsh

@@ -37,7 +37,8 @@
 : ${ZSH_HIGHLIGHT_STYLES[precommand]:=fg=green,underline}
 : ${ZSH_HIGHLIGHT_STYLES[commandseparator]:=none}
 : ${ZSH_HIGHLIGHT_STYLES[autodirectory]:=fg=green,underline}
-: ${ZSH_HIGHLIGHT_STYLES[path]:=underline}
+: ${ZSH_HIGHLIGHT_STYLES[path]:=underline,bold}
+: ${ZSH_HIGHLIGHT_STYLES[partial-path]:=underline}
 : ${ZSH_HIGHLIGHT_STYLES[path_pathseparator]:=}
 : ${ZSH_HIGHLIGHT_STYLES[path_prefix_pathseparator]:=}
 : ${ZSH_HIGHLIGHT_STYLES[globbing]:=fg=blue}
@@ -1093,6 +1094,8 @@ _zsh_highlight_main_highlighter_highlight_list()
                         else
                           if _zsh_highlight_main_highlighter_check_path $arg 1; then
                             style=$REPLY
+                          elif _zsh_highlight_main_highlighter_check_partial_path $arg 1; then
+                            style=$REPLY
                           else
                             style=unknown-token
                           fi
@@ -1202,9 +1205,33 @@ _zsh_highlight_main_highlighter_highlight_path_separators()
 # Check if $1 is a path.
 # If yes, return 0 and in $REPLY the style to use.
 # Else, return non-zero (and the contents of $REPLY is undefined).
+_zsh_highlight_main_highlighter_check_path()
+{
+  setopt localoptions nonomatch
+  _zsh_highlight_main_highlighter_expand_path "$1"
+  local expanded_path="$REPLY" tmp_path
+  integer in_command_position=$2
+
+  if (( in_command_position )); then
+    # ### Currently, this value is never returned: either it's overwritten
+    # ### below, or the return code is non-zero
+    REPLY=arg0
+  else
+    REPLY=path
+  fi
+
+  [[ -z $expanded_path ]] && return 1
+  [[ -e $expanded_path ]] && return 0
+
+  return 1
+}
+
+# Check if $1 is a partial path.
+# If yes, return 0 and in $REPLY the style to use.
+# Else, return non-zero (and the contents of $REPLY is undefined).
 #
 # $2 should be non-zero iff we're in command position.
-_zsh_highlight_main_highlighter_check_path()
+_zsh_highlight_main_highlighter_check_partial_path()
 {
   _zsh_highlight_main_highlighter_expand_path "$1"
   local expanded_path="$REPLY" tmp_path
@@ -1449,6 +1476,10 @@ _zsh_highlight_main_highlighter_highlight_argument()
       base_style=$REPLY
       _zsh_highlight_main_highlighter_highlight_path_separators $base_style
       highlights+=($reply)
+    elif _zsh_highlight_main_highlighter_check_partial_path $arg[$1,-1] 0; then
+      base_style=$REPLY
+      _zsh_highlight_main_highlighter_highlight_path_separators $base_style
+      highlights+=($reply)
     fi
   fi