Apply PR suggestions regarding semantic tokens

- Use edit-provided snapshot again in changeDocument
- Add omittingEmptyRanges to splitToSingleLineRanges
  Also optimize for the single-line case

Author: fwcd

Sources/SourceKitLSP/Swift/SwiftLanguageServer.swift

@@ -513,10 +513,9 @@ extension SwiftLanguageServer {
     let keys = self.keys
 
     self.queue.async {
-      let uri = note.textDocument.uri
       var lastResponse: SKDResponseDictionary? = nil
 
-      self.documentManager.edit(note) { (before: DocumentSnapshot, edit: TextDocumentContentChangeEvent) in
+      let snapshot = self.documentManager.edit(note) { (before: DocumentSnapshot, edit: TextDocumentContentChangeEvent) in
         let req = SKDRequestDictionary(sourcekitd: self.sourcekitd)
         req[keys.request] = self.requests.editor_replacetext
         req[keys.name] = note.textDocument.uri.pseudoPath
@@ -545,7 +544,7 @@ extension SwiftLanguageServer {
         }
       }
 
-      if let dict = lastResponse, let snapshot = self.documentManager.latestSnapshot(uri) {
+      if let dict = lastResponse, let snapshot = snapshot {
         let compileCommand = self.commandsByFile[note.textDocument.uri]
         self.publishDiagnostics(response: dict, for: snapshot, compileCommand: compileCommand)
       }

Sources/SourceKitLSP/Swift/SyntaxHighlightingToken.swift

@@ -235,14 +235,21 @@ extension Array where Element == SyntaxHighlightingToken {
 
 extension Range where Bound == Position {
   /// Splits a potentially multi-line range to multiple single-line ranges.
-  fileprivate func splitToSingleLineRanges(in snapshot: DocumentSnapshot) -> [Self] {
+  fileprivate func splitToSingleLineRanges(
+    in snapshot: DocumentSnapshot,
+    omittingEmptyRanges: Bool = true
+  ) -> [Self] {
+    if lowerBound.line == upperBound.line {
+      return omittingEmptyRanges && isEmpty ? [] : [self]
+    }
+
     guard let startIndex = snapshot.index(of: lowerBound),
           let endIndex = snapshot.index(of: upperBound) else {
       fatalError("Range \(self) reaches outside of the document")
     }
 
     let text = snapshot.text[startIndex..<endIndex]
-    let lines = text.split(separator: "\n")
+    let lines = text.split(separator: "\n", omittingEmptySubsequences: omittingEmptyRanges)
 
     return lines
       .enumerated()