Fix multiline DocC Returns rendering by preserving indentation

Sources/SwiftLanguageService/SymbolGraph.swift

@@ -82,12 +82,14 @@ private struct DocumentableSymbol {
     self.documentationComments = node.leadingTrivia.flatMap { trivia -> [String] in
       switch trivia {
       case .docLineComment(let comment):
-        return [String(comment.dropFirst(3).trimmingCharacters(in: .whitespaces))]
+        // Preserve leading whitespace for DocC indentation parsing (issue #2119)
+        return [String(comment.dropFirst(3))]
       case .docBlockComment(let comment):
         return comment.dropFirst(3)
           .dropLast(2)
           .split(whereSeparator: \.isNewline)
-          .map { String($0).trimmingCharacters(in: .whitespaces) }
+          // Preserve leading whitespace for DocC indentation parsing (issue #2119)
+          .map(String.init)
       default:
         return []
       }

Tests/SourceKitLSPTests/DoccDocumentationTests.swift

@@ -66,6 +66,72 @@ final class DoccDocumentationTests: SourceKitLSPTestCase {
     )
   }
 
+  func testMultilineReturnsInDocLineComment() async throws {
+    // Regression test for https://github.com/swiftlang/vscode-swift/issues/2119
+    let testClient = try await TestSourceKitLSPClient()
+    let uri = DocumentURI(for: .swift)
+    let positions = testClient.openDocument(
+      """
+      /// Checks whether a field exists.
+      ///
+      /// - Returns: One of the following
+      ///     * 1️⃣0: field does not exist
+      ///     * 1: field exists
+      public func hexists() -> Int { return 1 }
+      """,
+      uri: uri
+    )
+    let response = try await testClient.send(
+      DoccDocumentationRequest(
+        textDocument: TextDocumentIdentifier(uri),
+        position: positions["1️⃣"]
+      )
+    )
+    let renderNodeString = response.renderNode
+    XCTAssertTrue(
+      renderNodeString.contains("0: field does not exist"),
+      "Expected continuation text in render node"
+    )
+    XCTAssertFalse(
+      renderNodeString.contains("\"kind\" : \"content\""),
+      "Continuation lines should not create a separate Discussion section"
+    )
+  }
+
+  func testMultilineReturnsInDocBlockComment() async throws {
+    // Regression test for https://github.com/swiftlang/vscode-swift/issues/2119
+    let testClient = try await TestSourceKitLSPClient()
+    let uri = DocumentURI(for: .swift)
+    let positions = testClient.openDocument(
+      """
+      /**
+       Checks whether a field exists.
+
+       - Returns: One of the following
+           * 1️⃣0: field does not exist
+           * 1: field exists
+       */
+      public func hexists() -> Int { return 1 }
+      """,
+      uri: uri
+    )
+    let response = try await testClient.send(
+      DoccDocumentationRequest(
+        textDocument: TextDocumentIdentifier(uri),
+        position: positions["1️⃣"]
+      )
+    )
+    let renderNodeString = response.renderNode
+    XCTAssertTrue(
+      renderNodeString.contains("0: field does not exist"),
+      "Expected continuation text in render node"
+    )
+    XCTAssertFalse(
+      renderNodeString.contains("\"kind\" : \"content\""),
+      "Continuation lines should not create a separate Discussion section"
+    )
+  }
+
   func testStructure() async throws {
     try await renderDocumentation(
       markedText: """
@@ -551,6 +617,7 @@ final class DoccDocumentationTests: SourceKitLSPTestCase {
     )
   }
 
+
   // MARK: Markdown Articles and Extensions
 
   func testMarkdownArticle() async throws {