Improve search result by prioritizing exact matches (#1433)

I know adding 2 new phases for exact matches feels like a workaround,
but without a more thorough review on the entire searching algorithm
this is the best solution I have.

I also added basic tests for `search.js` using `mini_racer` gem (dev
dependency) to simulate JS evaluation. I chose this approach because it
should be simpler than maintaining a whole set of JS dependencies and
setups.

Fixes #1194

Author: st0012

Gemfile

@@ -11,3 +11,9 @@ gem 'rubocop', '>= 1.31.0'
 gem 'gettext'
 gem 'prism', '>= 0.30.0'
 gem 'webrick'
+
+platforms :ruby do
+  if Gem::Version.new(RUBY_VERSION) >= Gem::Version.new('3.2')
+    gem 'mini_racer' # For testing the searcher.js file
+  end
+end

lib/rdoc/generator/template/json_index/js/searcher.js

@@ -29,7 +29,7 @@ Searcher.prototype = new function() {
 
       var results =
         performSearch(_this.data, regexps, queries, highlighters, state);
-      var hasMore = (state.limit > 0 && state.pass < 4);
+      var hasMore = (state.limit > 0 && state.pass < 6);
 
       triggerResults.call(_this, results, !hasMore);
       if (hasMore) {
@@ -85,6 +85,30 @@ Searcher.prototype = new function() {
 
   /*  ----- Mathchers ------  */
 
+  /*
+   * This record matches if both the index and longIndex exactly equal queries[0]
+   * and the record matches all of the regexps. This ensures top-level exact matches
+   * like "String" are prioritized over nested classes like "Gem::Module::String".
+   */
+  function matchPassExact(index, longIndex, queries) {
+    return index == queries[0] && longIndex == queries[0];
+  }
+
+  /*
+   * This record matches if the index without "()" exactly equals queries[0].
+   * This prioritizes methods like "attribute()" when searching for "attribute".
+   */
+  function matchPassExactMethod(index, longIndex, queries, regexps) {
+    var indexWithoutParens = index.replace(/\(\)$/, '');
+    if (indexWithoutParens != queries[0]) return false;
+    if (index === indexWithoutParens) return false; // Not a method (no parens to remove)
+    for (var i=1, l = regexps.length; i < l; i++) {
+      if (!index.match(regexps[i]) && !longIndex.match(regexps[i]))
+        return false;
+    };
+    return true;
+  }
+
   /*
    * This record matches if the index starts with queries[0] and the record
    * matches all of the regexps
@@ -192,17 +216,26 @@ Searcher.prototype = new function() {
     var togo = CHUNK_SIZE;
     var matchFunc, hltFunc;
 
-    while (state.pass < 4 && state.limit > 0 && togo > 0) {
+    var isLowercaseQuery = queries[0] === queries[0].toLowerCase();
+
+    while (state.pass < 6 && state.limit > 0 && togo > 0) {
+      // When query is lowercase, prioritize methods over classes
       if (state.pass == 0) {
-        matchFunc = matchPassBeginning;
+        matchFunc = isLowercaseQuery ? matchPassExactMethod : matchPassExact;
         hltFunc = highlightQuery;
       } else if (state.pass == 1) {
-        matchFunc = matchPassLongIndex;
+        matchFunc = isLowercaseQuery ? matchPassExact : matchPassExactMethod;
         hltFunc = highlightQuery;
       } else if (state.pass == 2) {
-        matchFunc = matchPassContains;
+        matchFunc = matchPassBeginning;
         hltFunc = highlightQuery;
       } else if (state.pass == 3) {
+        matchFunc = matchPassLongIndex;
+        hltFunc = highlightQuery;
+      } else if (state.pass == 4) {
+        matchFunc = matchPassContains;
+        hltFunc = highlightQuery;
+      } else if (state.pass == 5) {
         matchFunc = matchPassRegexp;
         hltFunc = highlightRegexp;
       }