Rename SubstringMatch to SubsequenceMatch and use it to pre-filter completion items

Fix #321

src/lex_utils.cc

@@ -188,31 +188,17 @@ std::string LexWordAroundPos(lsPosition position, const std::string& content) {
   return content.substr(start, end - start + 1);
 }
 
-bool SubstringMatch(const std::string& search, const std::string& content) {
-  if (search.empty())
-    return true;
-
-  size_t search_index = 0;
-  char search_char = tolower(search[search_index]);
-
-  size_t content_index = 0;
-
-  while (true) {
-    char content_char = tolower(content[content_index]);
-
-    if (content_char == search_char) {
-      search_index += 1;
-      if (search_index >= search.size())
-        return true;
-      search_char = tolower(search[search_index]);
-    }
-
-    content_index += 1;
-    if (content_index >= content.size())
+bool SubsequenceMatch(const std::string& search, const std::string& content) {
+  size_t j = 0;
+  for (size_t i = 0; i < search.size(); i++) {
+    char search_char = tolower(search[i]);
+    while (j < content.size() && tolower(content[j]) != search_char)
+      j++;
+    if (j == content.size())
       return false;
+    j++;
   }
-
-  return false;
+  return true;
 }
 
 TEST_SUITE("Offset") {
@@ -239,32 +225,32 @@ TEST_SUITE("Offset") {
 TEST_SUITE("Substring") {
   TEST_CASE("match") {
     // Sanity.
-    REQUIRE(SubstringMatch("a", "aa"));
-    REQUIRE(SubstringMatch("aa", "aa"));
+    REQUIRE(SubsequenceMatch("a", "aa"));
+    REQUIRE(SubsequenceMatch("aa", "aa"));
 
     // Empty string matches anything.
-    REQUIRE(SubstringMatch("", ""));
-    REQUIRE(SubstringMatch("", "aa"));
+    REQUIRE(SubsequenceMatch("", ""));
+    REQUIRE(SubsequenceMatch("", "aa"));
 
     // Match in start/middle/end.
-    REQUIRE(SubstringMatch("a", "abbbb"));
-    REQUIRE(SubstringMatch("a", "bbabb"));
-    REQUIRE(SubstringMatch("a", "bbbba"));
-    REQUIRE(SubstringMatch("aa", "aabbb"));
-    REQUIRE(SubstringMatch("aa", "bbaab"));
-    REQUIRE(SubstringMatch("aa", "bbbaa"));
+    REQUIRE(SubsequenceMatch("a", "abbbb"));
+    REQUIRE(SubsequenceMatch("a", "bbabb"));
+    REQUIRE(SubsequenceMatch("a", "bbbba"));
+    REQUIRE(SubsequenceMatch("aa", "aabbb"));
+    REQUIRE(SubsequenceMatch("aa", "bbaab"));
+    REQUIRE(SubsequenceMatch("aa", "bbbaa"));
 
     // Capitalization.
-    REQUIRE(SubstringMatch("aa", "aA"));
-    REQUIRE(SubstringMatch("aa", "Aa"));
-    REQUIRE(SubstringMatch("aa", "AA"));
+    REQUIRE(SubsequenceMatch("aa", "aA"));
+    REQUIRE(SubsequenceMatch("aa", "Aa"));
+    REQUIRE(SubsequenceMatch("aa", "AA"));
 
     // Token skipping.
-    REQUIRE(SubstringMatch("ad", "abcd"));
-    REQUIRE(SubstringMatch("ad", "ABCD"));
+    REQUIRE(SubsequenceMatch("ad", "abcd"));
+    REQUIRE(SubsequenceMatch("ad", "ABCD"));
 
     // Ordering.
-    REQUIRE(!SubstringMatch("ad", "dcba"));
+    REQUIRE(!SubsequenceMatch("ad", "dcba"));
   }
 }
 

src/lex_utils.h

@@ -24,4 +24,5 @@ void LexFunctionDeclaration(const std::string& buffer_content,
 
 std::string LexWordAroundPos(lsPosition position, const std::string& content);
 
-bool SubstringMatch(const std::string& search, const std::string& content);
+// Case-insensitive subsequence matching.
+bool SubsequenceMatch(const std::string& search, const std::string& content);

src/messages/text_document_completion.cc

@@ -128,6 +128,13 @@ void FilterAndSortCompletionResponse(
     return;
   }
 
+  items.erase(std::remove_if(items.begin(), items.end(),
+                             [&](const lsCompletionItem& item) {
+                               return !SubsequenceMatch(complete_text,
+                                                        item.label);
+                             }),
+              items.end());
+
   // Find the appearance of |complete_text| in all candidates.
   bool found = false;
   for (auto& item : items) {
@@ -187,7 +194,6 @@ void FilterAndSortCompletionResponse(
       // Find fuzzy matches if we haven't found all of the literal matches.
       if (filtered_result.size() < kMaxResultSize) {
         for (const auto& item : items) {
-          if (SubstringMatch(complete_text, item.label)) {
           // Don't insert the same completion entry.
           if (!inserted.insert(item.InsertedContent()).second)
             continue;
@@ -197,7 +203,6 @@ void FilterAndSortCompletionResponse(
             break;
         }
       }
-      }
 
       items = filtered_result;
     }

src/messages/workspace_symbol.cc

@@ -225,7 +225,7 @@ struct WorkspaceSymbolHandler : BaseMessageHandler<Ipc_WorkspaceSymbol> {
           query_without_space += c;
 
       for (int i = 0; i < db->short_names.size(); ++i) {
-        if (SubstringMatch(query_without_space, db->short_names[i])) {
+        if (SubsequenceMatch(query_without_space, db->short_names[i])) {
           // Do not show the same entry twice.
           if (!inserted_results.insert(db->detailed_names[i]).second)
             continue;