Rename Get{Buffer,Index}LineFrom{Index,Buffer}Line in preparation for column alignment.

src/messages/text_document_document_link.cc

@@ -62,7 +62,7 @@ struct TextDocumentDocumentLinkHandler
       }
       for (const IndexInclude& include : file->def->includes) {
         optional<int> buffer_line =
-            working_file->GetBufferLineFromIndexLine(include.line);
+            working_file->GetBufferPosFromIndexPos(include.line, nullptr);
         if (!buffer_line)
           continue;
 

src/query_utils.cc

@@ -318,11 +318,12 @@ optional<lsPosition> GetLsPosition(WorkingFile* working_file,
   if (!working_file)
     return lsPosition(position.line, position.column);
 
-  optional<int> start = working_file->GetBufferLineFromIndexLine(position.line);
+  int column = position.column;
+  optional<int> start = working_file->GetBufferPosFromIndexPos(position.line, &column);
   if (!start)
     return nullopt;
 
-  return lsPosition(*start, position.column);
+  return lsPosition(*start, column);
 }
 
 optional<lsRange> GetLsRange(WorkingFile* working_file, const Range& location) {
@@ -332,10 +333,11 @@ optional<lsRange> GetLsRange(WorkingFile* working_file, const Range& location) {
         lsPosition(location.end.line, location.end.column));
   }
 
+  int start_column = location.start.column, end_column = location.end.column;
   optional<int> start =
-      working_file->GetBufferLineFromIndexLine(location.start.line);
+      working_file->GetBufferPosFromIndexPos(location.start.line, &start_column);
   optional<int> end =
-      working_file->GetBufferLineFromIndexLine(location.end.line);
+      working_file->GetBufferPosFromIndexPos(location.end.line, &end_column);
   if (!start || !end)
     return nullopt;
 
@@ -348,8 +350,8 @@ optional<lsRange> GetLsRange(WorkingFile* working_file, const Range& location) {
   if (*end < *start)
     *end = *start + (location.end.line - location.start.line);
 
-  return lsRange(lsPosition(*start, location.start.column),
+  return lsRange(lsPosition(*start, start_column),
-                 lsPosition(*end, location.end.column));
+                 lsPosition(*end, end_column));
 }
 
 lsDocumentUri GetLsDocumentUri(QueryDatabase* db,
@@ -482,7 +484,7 @@ std::vector<SymbolRef> FindSymbolsAtLocation(WorkingFile* working_file,
   int target_column = position.character;
   if (working_file) {
     optional<int> index_line =
-        working_file->GetIndexLineFromBufferLine(target_line);
+        working_file->GetIndexPosFromBufferPos(target_line, &target_column);
     if (index_line)
       target_line = *index_line;
   }

src/working_files.cc

@@ -8,6 +8,7 @@
 
 #include <algorithm>
 #include <climits>
+#include <numeric>
 
 namespace {
 
@@ -68,12 +69,34 @@ int MyersDiff(const std::string& a, const std::string& b, int threshold) {
   return MyersDiff(a.data(), a.size(), b.data(), b.size(), threshold);
 }
 
+// Computes Levenshtein edit distance with O(N*M) Needleman-Wunsch algorithm
+// and returns a distance vector where d[i] = cost of aligning a to b[0,i).
+//
+// Myers' diff algorithm is used to find best matching line while this one is
+// used to align a single column because Myers' needs some twiddling to return
+// distance vector.
+std::vector<int> LevenshteinDistance(std::string a, std::string b) {
+  std::vector<int> d(b.size() + 1);
+  std::iota(d.begin(), d.end(), 0);
+  for (int i = 0; i < (int)a.size(); i++) {
+    int ul = d[0];
+    d[0] = i + 1;
+    for (int j = 0; j < (int)b.size(); j++) {
+      int t = d[j + 1];
+      d[j + 1] = a[i] == b[j] ? ul : std::min(ul, std::min(d[j], d[j + 1])) + 1;
+      ul = t;
+    }
+  }
+  return d;
+}
+
 // Find matching buffer line of index_lines[line].
 // By symmetry, this can also be used to find matching index line of a buffer
 // line.
 optional<int> FindMatchingLine(const std::vector<std::string>& index_lines,
                                const std::vector<int>& index_to_buffer,
                                int line,
+                               int* column,
                                const std::vector<std::string>& buffer_lines) {
   // If this is a confident mapping, returns.
   if (index_to_buffer[line] >= 0)
@@ -225,7 +248,7 @@ void WorkingFile::ComputeLineMapping() {
       buffer_to_index[index_to_buffer[i]] = i;
 }
 
-optional<int> WorkingFile::GetBufferLineFromIndexLine(int line) {
+optional<int> WorkingFile::GetBufferPosFromIndexPos(int line, int* column) {
   // The implementation is simple but works pretty well for most cases. We
   // lookup the line contents in the indexed file contents, and try to find the
   // most similar line in the current buffer file.
@@ -248,10 +271,10 @@ optional<int> WorkingFile::GetBufferLineFromIndexLine(int line) {
 
   if (index_to_buffer.empty())
     ComputeLineMapping();
-  return FindMatchingLine(index_lines, index_to_buffer, line, buffer_lines);
+  return FindMatchingLine(index_lines, index_to_buffer, line, column, buffer_lines);
 }
 
-optional<int> WorkingFile::GetIndexLineFromBufferLine(int line) {
+optional<int> WorkingFile::GetIndexPosFromBufferPos(int line, int* column) {
   // See GetBufferLineFromIndexLine for additional comments.
 
   // Note: |index_line| and |buffer_line| are 1-based.
@@ -265,7 +288,7 @@ optional<int> WorkingFile::GetIndexLineFromBufferLine(int line) {
 
   if (buffer_to_index.empty())
     ComputeLineMapping();
-  return FindMatchingLine(buffer_lines, buffer_to_index, line, index_lines);
+  return FindMatchingLine(buffer_lines, buffer_to_index, line, column, index_lines);
 }
 
 std::string WorkingFile::FindClosestCallNameInBuffer(

src/working_files.h

@@ -38,12 +38,12 @@ struct WorkingFile {
   // This should be called whenever |buffer_content| has changed.
   void OnBufferContentUpdated();
 
-  // Find the buffer-line which should be shown for |indexed_line|. This
+  // Finds the buffer line number which maps to index line number |line|.
-  // accepts and returns 1-based lines.
+  // Also resolves |column| if not NULL.
-  optional<int> GetBufferLineFromIndexLine(int indexed_line);
+  optional<int> GetBufferPosFromIndexPos(int line, int* column);
-  // Find the indexed-line which should be shown for |buffer_line|. This
+  // Finds the index line number which maps to buffer line number |line|.
-  // accepts and returns 1-based lines.
+  // Also resolves |column| if not NULL.
-  optional<int> GetIndexLineFromBufferLine(int buffer_line);
+  optional<int> GetIndexPosFromBufferPos(int line, int* column);
 
   // TODO: Move FindClosestCallNameInBuffer and FindStableCompletionSource into
   // lex_utils.h/cc