fix: avoid falling back to fallback unnecessarily

As noted here:

- #420 (comment)

It's possible to hit the max file limit (coming soon to a repo near you)
but have all the results hidden because they're in dot directories. As
such, `#results` can be 0 even though the scanner found stuff.

Avoid this by also returning candidate count, and not falling back
unless that is 0 as well.

bin/benchmarks/matcher.lua

@@ -42,14 +42,14 @@ benchmark({
       local input = ''
       for letter in query:gmatch('.') do
         local matches = lib.matcher_run(matcher, input)
-        for k = 0, matches.count - 1 do
+        for k = 0, matches.match_count - 1 do
           local str = matches.matches[k]
           ffi.string(str.contents, str.length)
         end
         input = input .. letter
       end
       local matches = lib.matcher_run(matcher, input)
-      for k = 0, matches.count - 1 do
+      for k = 0, matches.match_count - 1 do
         local str = matches.matches[k]
         ffi.string(str.contents, str.length)
       end

lua/wincent/commandt/lib/matcher.c

@@ -236,11 +236,12 @@ result_t *commandt_matcher_run(matcher_t *matcher, const char *needle) {
     result_t *results = xmalloc(sizeof(result_t));
     unsigned count = matches_count > limit ? limit : matches_count;
     results->matches = xmalloc(count * sizeof(const char *));
-    results->count = 0;
+    results->match_count = 0;
+    results->candidate_count = candidate_count;
 
-    for (long i = 0; i < count && results->count <= limit; i++) {
+    for (long i = 0; i < count && results->match_count <= limit; i++) {
         if (matches[i]->score > 0.0f) {
-            results->matches[results->count++] = matches[i]->candidate;
+            results->matches[results->match_count++] = matches[i]->candidate;
         }
     }
 

lua/wincent/commandt/lib/matcher.h

@@ -14,7 +14,8 @@
 // TODO: may later want to return highlight positions as well
 typedef struct {
     str_t **matches;
-    unsigned count;
+    unsigned match_count;
+    unsigned candidate_count;
 } result_t;
 
 /**

lua/wincent/commandt/private/finders/command.lua

@@ -15,11 +15,11 @@ return function(directory, command, options)
   finder.run = function(query)
     local results = lib.matcher_run(finder.matcher, query)
     local strings = {}
-    for i = 0, results.count - 1 do
+    for i = 0, results.match_count - 1 do
       local str = results.matches[i]
       table.insert(strings, ffi.string(str.contents, str.length))
     end
-    return strings
+    return strings, results.candidate_count
   end
   finder.open = options.open
   return finder

lua/wincent/commandt/private/finders/file.lua

@@ -13,11 +13,11 @@ return function(directory, options)
   finder.run = function(query)
     local results = lib.matcher_run(finder.matcher, query)
     local strings = {}
-    for i = 0, results.count - 1 do
+    for i = 0, results.match_count - 1 do
       local str = results.matches[i]
       table.insert(strings, ffi.string(str.contents, str.length))
     end
-    return strings
+    return strings, results.candidate_count
   end
   finder.open = options.open
   return finder

lua/wincent/commandt/private/finders/list.lua

@@ -17,11 +17,11 @@ return function(directory, candidates, options)
   finder.run = function(query)
     local results = lib.matcher_run(finder.matcher, query)
     local strings = {}
-    for i = 0, results.count - 1 do
+    for i = 0, results.match_count - 1 do
       local str = results.matches[i]
       table.insert(strings, ffi.string(str.contents, str.length))
     end
-    return strings
+    return strings, results.candidate_count
   end
   finder.open = options.open
   return finder

lua/wincent/commandt/private/finders/watchman.lua

@@ -14,11 +14,11 @@ return function(directory, options)
   finder.run = function(query)
     local results = lib.matcher_run(finder.matcher, query)
     local strings = {}
-    for i = 0, results.count - 1 do
+    for i = 0, results.match_count - 1 do
       local str = results.matches[i]
       table.insert(strings, ffi.string(str.contents, str.length))
     end
-    return strings
+    return strings, results.candidate_count
   end
   finder.open = options.open
   return finder

lua/wincent/commandt/private/lib.lua

@@ -56,7 +56,8 @@ setmetatable(c, {
 
       typedef struct {
           str_t **matches;
-          unsigned count;
+          unsigned match_count;
+          unsigned candidate_count;
       } result_t;
 
       typedef struct {

lua/wincent/commandt/private/ui.lua

@@ -6,6 +6,7 @@ local ui = {}
 local MatchListing = require('wincent.commandt.private.match_listing').MatchListing
 local Prompt = require('wincent.commandt.private.prompt').Prompt
 
+local candidate_count = nil
 local cmdline_enter_autocmd = nil
 local current_finder = nil -- Reference to avoid premature garbage collection.
 local current_window = nil
@@ -94,8 +95,8 @@ ui.show = function(finder, options)
     margin = options.margin,
     name = options.name,
     on_change = function(query)
-      results = current_finder.run(query)
-      if #results > 0 then
+      results, candidate_count = current_finder.run(query)
+      if #results > 0 or candidate_count > 0 then
         -- Once we've proved a finder works, we don't ever want to use fallback.
         current_finder.fallback = nil
       elseif current_finder.fallback then

lua/wincent/commandt/test/matcher.lua

@@ -14,7 +14,7 @@ describe('matcher.c', function()
       match = function(query)
         local results = lib.matcher_run(matcher, query)
         local strings = {}
-        for k = 0, results.count - 1 do
+        for k = 0, results.match_count - 1 do
           local str = results.matches[k]
           table.insert(strings, ffi.string(str.contents, str.length))
         end