If query empty, Results sorted lexicographically

This change was also the root cause of the crash bug I spent two days tracking
down. The problem was that the new bool member was not added to the custom copy
ctor... since we don't really need a custom copy ctor for Result, we're going
with the compiler-provided one.

cpp/ycm/Result.cpp

@@ -72,6 +72,7 @@ int NumWordBoundaryCharMatches( const std::string &query,
 
 Result::Result( bool is_subsequence )
   :
+  query_is_empty_( true ),
   is_subsequence_( is_subsequence ),
   first_char_same_in_query_and_text_( false ),
   ratio_of_word_boundary_chars_in_query_( 0 ),
@@ -90,6 +91,7 @@ Result::Result( bool is_subsequence,
                 const std::string &word_boundary_chars,
                 const std::string &query )
   :
+  query_is_empty_( true ),
   is_subsequence_( is_subsequence ),
   first_char_same_in_query_and_text_( false ),
   ratio_of_word_boundary_chars_in_query_( 0 ),
@@ -104,29 +106,14 @@ Result::Result( bool is_subsequence,
 }
 
 
-// TODO: do we need a custom copy ctor?
-Result::Result( const Result& other )
-  :
-  is_subsequence_( other.is_subsequence_ ),
-  first_char_same_in_query_and_text_(
-      other.first_char_same_in_query_and_text_ ),
-  ratio_of_word_boundary_chars_in_query_(
-      other.ratio_of_word_boundary_chars_in_query_ ),
-  word_boundary_char_utilization_( other.word_boundary_char_utilization_ ),
-  query_is_candidate_prefix_( other.query_is_candidate_prefix_ ),
-  text_is_lowercase_( other.text_is_lowercase_ ),
-  char_match_index_sum_( other.char_match_index_sum_ ),
-  text_( other.text_ )
-{
-}
-
-
 bool Result::operator< ( const Result &other ) const
 {
   // Yes, this is ugly but it also needs to be fast.  Since this is called a
   // bazillion times, we have to make sure only the required comparisons are
   // made, and no more.
 
+  if ( !query_is_empty_ )
+  {
     if ( first_char_same_in_query_and_text_ !=
         other.first_char_same_in_query_and_text_ )
     {
@@ -182,7 +169,9 @@ bool Result::operator< ( const Result &other ) const
 
     if ( text_is_lowercase_ != other.text_is_lowercase_ )
       return text_is_lowercase_;
+  }
 
+  // Lexicographic comparison
   return *text_ < *other.text_;
 }
 
@@ -191,6 +180,8 @@ void Result::SetResultFeaturesFromQuery(
     const std::string &word_boundary_chars,
     const std::string &query)
 {
+  query_is_empty_ = query.empty();
+
   if ( query.empty() || text_->empty() )
     return;
 

cpp/ycm/Result.h

@@ -35,8 +35,6 @@ public:
           const std::string &word_boundary_chars,
           const std::string &query );
 
-  Result( const Result& other );
-
   bool operator< ( const Result &other ) const;
 
   inline bool IsSubsequence() const
@@ -54,6 +52,9 @@ private:
       const std::string &query,
       const std::string &word_boundary_chars );
 
+  // true when the query for which the result was created was an empty string;
+  // in these cases we just use a lexicographic comparison
+  bool query_is_empty_;
 
   // true when the characters of the query are a subsequence of the characters
   // in the candidate text, e.g. the characters "abc" are a subsequence for

python/ycm.py

@@ -94,6 +94,7 @@ class ClangCompleter( Completer ):
     self.completer = indexer.ClangCompleter()
 
   def CandidatesForQuery( self, query ):
+    # TODO: sanitize query
     files = indexer.UnsavedFileVec()
 
     # CAREFUL HERE! For UnsavedFile filename and contents we are referring