Support folding of collection literals

Author: ahoppen

Sources/SourceKitLSP/Swift/FoldingRange.swift

@@ -134,6 +134,20 @@ fileprivate final class FoldingRangeFinder: SyntaxAnyVisitor {
     return .visitChildren
   }
 
+  override func visit(_ node: ArrayExprSyntax) -> SyntaxVisitorContinueKind {
+    return self.addFoldingRange(
+      start: node.leftSquare.endPositionBeforeTrailingTrivia.utf8Offset,
+      end: node.rightSquare.positionAfterSkippingLeadingTrivia.utf8Offset
+    )
+  }
+
+  override func visit(_ node: DictionaryExprSyntax) -> SyntaxVisitorContinueKind {
+    return self.addFoldingRange(
+      start: node.leftSquare.endPositionBeforeTrailingTrivia.utf8Offset,
+      end: node.rightSquare.positionAfterSkippingLeadingTrivia.utf8Offset
+    )
+  }
+
   override func visit(_ node: FunctionCallExprSyntax) -> SyntaxVisitorContinueKind {
     return self.addFoldingRange(
       start: node.arguments.position.utf8Offset,

Tests/SourceKitLSPTests/FoldingRangeTests.swift

@@ -66,7 +66,9 @@ func assertFoldingRanges(
       Expected \(expectedRanges.count) ranges but got \(foldingRanges.count)
 
       \(foldingRanges)
-      """
+      """,
+      file: file,
+      line: line
     )
     return
   }
@@ -258,7 +260,27 @@ final class FoldingRangeTests: XCTestCase {
     )
   }
 
-  func testFoldCollections() {
-    // let testClient
+  func testFoldCollections() async throws {
+    try await assertFoldingRanges(
+      markedSource: """
+        let x = [1️⃣1, 2, 32️⃣]
+        """,
+      expectedRanges: [
+        FoldingRangeSpec(from: "1️⃣", to: "2️⃣")
+      ]
+    )
+
+    try await assertFoldingRanges(
+      markedSource: """
+        let x = [1️⃣
+          1: "one", 
+          2: "two", 
+          3: "three"
+        2️⃣]
+        """,
+      expectedRanges: [
+        FoldingRangeSpec(from: "1️⃣", to: "2️⃣")
+      ]
+    )
   }
 }