Support folding of switch cases

Author: ahoppen

Sources/SourceKitLSP/Swift/FoldingRange.swift

@@ -162,6 +162,13 @@ fileprivate final class FoldingRangeFinder: SyntaxAnyVisitor {
     )
   }
 
+  override func visit(_ node: SwitchCaseSyntax) -> SyntaxVisitorContinueKind {
+    return self.addFoldingRange(
+      start: node.label.endPositionBeforeTrailingTrivia.utf8Offset,
+      end: node.statements.endPosition.utf8Offset
+    )
+  }
+
   __consuming func finalize() -> Set<FoldingRange> {
     return self.ranges
   }

Tests/SourceKitLSPTests/FoldingRangeTests.swift

@@ -283,4 +283,24 @@ final class FoldingRangeTests: XCTestCase {
       ]
     )
   }
+
+  func testFoldSwitchCase() async throws {
+    try await assertFoldingRanges(
+      markedSource: """
+        switch foo {1️⃣
+        case 1:2️⃣
+          break 3️⃣
+        default:4️⃣
+          let x = 1
+          print(5️⃣x6️⃣)7️⃣
+        8️⃣}
+        """,
+      expectedRanges: [
+        FoldingRangeSpec(from: "1️⃣", to: "8️⃣"),
+        FoldingRangeSpec(from: "2️⃣", to: "3️⃣"),
+        FoldingRangeSpec(from: "4️⃣", to: "7️⃣"),
+        FoldingRangeSpec(from: "5️⃣", to: "6️⃣"),
+      ]
+    )
+  }
 }