Fix splitToSingleLineRanges

Previously, subsequent newlines would cause positions computed by
splitToSingleLineRanges to become incorrect if omittingEmptyRanges was
set.

Additionally, add a test case for multi-line range splitting

Author: fwcd

Sources/SourceKitLSP/Swift/SyntaxHighlightingTokenParser.swift

@@ -207,10 +207,14 @@ extension Range where Bound == Position {
   /// Splits a potentially multi-line range to multiple single-line ranges.
   fileprivate func splitToSingleLineRanges(
     in snapshot: DocumentSnapshot,
-    omittingEmptyRanges: Bool = true
+    omittingEmptyRange: Bool = true
   ) -> [Self] {
+    if omittingEmptyRange && isEmpty {
+      return []
+    }
+
     if lowerBound.line == upperBound.line {
-      return omittingEmptyRanges && isEmpty ? [] : [self]
+      return [self]
     }
 
     guard let startIndex = snapshot.index(of: lowerBound),
@@ -219,7 +223,7 @@ extension Range where Bound == Position {
     }
 
     let text = snapshot.text[startIndex..<endIndex]
-    let lines = text.split(separator: "\n", omittingEmptySubsequences: omittingEmptyRanges)
+    let lines = text.split(separator: "\n", omittingEmptySubsequences: false)
 
     return lines
       .enumerated()
@@ -235,4 +239,12 @@ extension Range where Bound == Position {
         return start..<end
       }
   }
+
+  /// **Public for testing**
+  public func _splitToSingleLineRanges(
+    in snapshot: DocumentSnapshot,
+    omittingEmptyRange: Bool = true
+  ) -> [Self] {
+    splitToSingleLineRanges(in: snapshot, omittingEmptyRange: omittingEmptyRange)
+  }
 }

Tests/SourceKitLSPTests/SemanticTokensTests.swift

@@ -188,6 +188,42 @@ final class SemanticTokensTests: XCTestCase {
     XCTAssertEqual(decoded, tokens)
   }
 
+  func testRangeSplitting() {
+    let text = """
+    struct X {
+      let x: Int
+      let y: String
+
+
+    }
+    """
+    openDocument(text: text)
+
+    guard let snapshot = connection.server?.workspace?.documentManager.latestSnapshot(uri) else {
+      fatalError("Could not fetch document snapshot for \(#function)")
+    }
+
+    let empty = Position(line: 0, utf16index: 1)..<Position(line: 0, utf16index: 1)
+    XCTAssertEqual(empty._splitToSingleLineRanges(in: snapshot, omittingEmptyRange: true), [])
+    XCTAssertEqual(empty._splitToSingleLineRanges(in: snapshot, omittingEmptyRange: false), [empty])
+
+    for omittingEmptyRange in [false, true] {
+      let multiLine = Position(line: 1, utf16index: 6)..<Position(line: 2, utf16index: 7)
+      XCTAssertEqual(multiLine._splitToSingleLineRanges(in: snapshot, omittingEmptyRange: omittingEmptyRange), [
+        Position(line: 1, utf16index: 6)..<Position(line: 1, utf16index: 12),
+        Position(line: 2, utf16index: 0)..<Position(line: 2, utf16index: 7),
+      ])
+
+      let emptyLines = Position(line: 2, utf16index: 14)..<Position(line: 5, utf16index: 1)
+      XCTAssertEqual(emptyLines._splitToSingleLineRanges(in: snapshot, omittingEmptyRange: omittingEmptyRange), [
+        Position(line: 2, utf16index: 14)..<Position(line: 2, utf16index: 15),
+        Position(line: 3, utf16index: 0)..<Position(line: 3, utf16index: 0),
+        Position(line: 4, utf16index: 0)..<Position(line: 4, utf16index: 0),
+        Position(line: 5, utf16index: 0)..<Position(line: 5, utf16index: 1),
+      ])
+    }
+  }
+
   func testEmpty() {
     let text = ""
     let tokens = openAndPerformSemanticTokensRequest(text: text)

Tests/SourceKitLSPTests/XCTestManifests.swift

@@ -166,6 +166,7 @@ extension SemanticTokensTests {
       ("testInsertSpaceBeforeToken", testInsertSpaceBeforeToken),
       ("testIntArrayCoding", testIntArrayCoding),
       ("testRanged", testRanged),
+      ("testRangeSplitting", testRangeSplitting),
       ("testRemoveNewline", testRemoveNewline),
       ("testReplaceUntilEndOfToken", testReplaceUntilEndOfToken),
       ("testReplaceUntilMiddleOfToken", testReplaceUntilMiddleOfToken),