Fix foo -x: argmatcher syntax.

Clink 0.4.9 accidentally interpreted the next part as the next arg
position.  But that's because Clink and Readline got out of sync about
which word was being completed.

Clink 1.x didn't do any completion.  Although that was actually the
intended behavior, I want to strike a balance between compatibility and
reasonable behavior.

So now Clink recognizes the `-x:` flag syntax and does file completion,
and also colors the whole argument as a flag, regardless what follows
the `:` or `=` character.  To generate other matches, a lua script can
register a generator and provide code to handle the case.

This fixes issues #61 and #62.

TODO.md

@@ -5,8 +5,6 @@ _This todo list describes ChrisAnt996's current intended roadmap for Clink's fut
 # RELEASE
 
 ## Issues
-- Argmatcher should have a new mechanism for generating matches for `-foo:right_here` so that it doesn't treat it like an argument position.  Maybe `"-foo:"+function_name`, and by default it uses `file_match_generator()`.
-- Argmatcher should color `-foo:` as a Flag and `right_here` as Other.
 - Provide a way for a custom classifier to apply a classification anywhere (not just to a pre-parsed word), and to apply any arbitrary CSI SGR code to a word or to anywhere.
 - An unbound multi-char key sequence is fully ignored if it's the first key sequence in a chord.  But if a chord is already being resolved, then an unbound multi-char key sequence (such as Right Arrow or Escape or etc) inserts whatever part of the key sequence failed to resolve.  It should discard the full key sequence, just like when there's no chord being resolved yet.
 

clink/lib/src/line_editor_impl.cpp

@@ -569,7 +569,7 @@ unsigned int line_editor_impl::collect_words(words& words, matches_impl& matches
         {
             for (const char* walk = word_start; *walk && !isspace((unsigned char)*walk); walk++)
             {
-                if (*walk == ':' || *walk == '=')
+                if (strchr(":=", *walk))
                 {
                     if (walk[1] &&
                         (rl_completer_quote_characters && strchr(rl_completer_quote_characters, walk[1])) ||

clink/lua/scripts/arguments.lua

@@ -101,15 +101,36 @@ function _argreader:update(word, word_index)
             if arg._links and arg._links[word] then
                 t = arg_match_type
             else
-                for _, i in ipairs(arg) do
-                    if type(i) == "function" then
-                        -- For performance reasons, don't run argmatcher functions
-                        -- during classify.  If that's needed, a script can provide
-                        -- a :classify function to complement a :generate function.
-                        t = 'o' --other (placeholder; superseded by :classifyword).
-                    elseif i == word then
-                        t = arg_match_type
-                        break
+                -- For performance reasons, don't run argmatcher functions
+                -- during classify.  If that's needed, a script can provide a
+                -- :classify function to complement a :generate function.
+                --
+                -- Also, when the word is a flag and contains : or = then check
+                -- if the portion up to and including the : or = is a known
+                -- flag.  When so, color the whole thing as a flag.
+                --
+                local matched = false
+                if arg_match_type == "f" then
+                    local attached_pos = word:find("[:=]")
+                    if attached_pos then
+                        local prefix = word:sub(1, attached_pos)
+                        for _, i in ipairs(arg) do
+                            if type(i) ~= "function" and i == prefix then
+                                t = arg_match_type
+                                matched = true
+                                break
+                            end
+                        end
+                    end
+                end
+                if not matched then
+                    for _, i in ipairs(arg) do
+                        if type(i) == "function" then
+                            t = 'o' --other (placeholder; superseded by :classifyword).
+                        elseif i == word then
+                            t = arg_match_type
+                            break
+                        end
                     end
                 end
             end
@@ -462,6 +483,21 @@ function _argmatcher:_generate(line_state, match_builder)
         add_matches(matcher._flags._args[1], match_type)
         return true
     else
+        -- When endword is adjacent the previous word and the previous word ends
+        -- with : or = then this is a flag-attached arg, not an arg position.
+        if line_state:getwordcount() > 1 then
+            local prevwordinfo = line_state:getwordinfo(line_state:getwordcount() - 1)
+            local endwordinfo = line_state:getwordinfo(line_state:getwordcount())
+            if prevwordinfo.offset + prevwordinfo.length == endwordinfo.offset and
+                    matcher:_is_flag(line_state:getword(line_state:getwordcount() - 1)) and
+                    line_state:getline():sub(endwordinfo.offset - 1, endwordinfo.offset - 1):find("[:=]") then
+                -- FUTURE:  Could have a new argmatcher syntax to generate
+                -- matches for "-x:" flags, but it's such a niche scenario that
+                -- it seems reasonable to require a custom :generate() function.
+                match_builder:addmatches(clink.filematches(line_state:getendword()))
+                return true
+            end
+        end
         local arg = matcher._args[arg_index]
         if arg then
             return add_matches(arg, match_type) and true or false
@@ -769,6 +805,12 @@ function argmatcher_generator:getwordbreakinfo(line_state)
         if argmatcher and argmatcher._flags then
             local word = line_state:getendword()
             if argmatcher:_is_flag(word) then
+                -- Accommodate `-flag:text` and `-flag=text` (with or without
+                -- quotes) so that matching can happen for the `text` portion.
+                local attached_arg,attach_pos = word:find("^[^:=][^:=]+[:=]")
+                if attached_arg then
+                    return attach_pos, 0
+                end
                 return 0, 1
             end
         end