Add buildFinalResult to CodeBlockItemListBuilder to ensure newline between expressions

Author: mateusrodriguesxyz

Sources/SwiftSyntaxBuilder/ResultBuilderExtensions.swift

@@ -40,6 +40,18 @@ extension CodeBlockItemListBuilder {
   public static func buildExpression(_ expression: some Sequence<DeclSyntaxProtocol>) -> Component {
     buildExpression(expression.map { CodeBlockItemSyntax(item: .decl(DeclSyntax($0))) })
   }
+
+  public static func buildFinalResult(_ component: Component) -> CodeBlockItemListSyntax {
+    .init(
+      component.enumerated().map { (index, expression) in
+        if index > component.startIndex, !expression.leadingTrivia.contains(where: \.isNewline) {
+          return expression.with(\.leadingTrivia, .newline.merging(expression.leadingTrivia))
+        } else {
+          return expression
+        }
+      }
+    )
+  }
 }
 
 extension ConditionElementListBuilder {

Tests/SwiftSyntaxBuilderTest/CollectionNodeFlatteningTests.swift

@@ -75,4 +75,31 @@ final class CollectionNodeFlatteningTests: XCTestCase {
       """
     )
   }
+
+  func test_FlattenCodeBlockItemListWithCodeBlockInterpolated() {
+    let block = CodeBlockItemListSyntax {
+      "let a = 1"
+      "let b = 2"
+      "let c = 3"
+    }
+
+    let buildable = CodeBlockItemListSyntax {
+      "let one = object.methodOne()"
+      "let two = object.methodTwo()"
+      "let three = {\(block)}()"
+    }
+
+    assertBuildResult(
+      buildable,
+      """
+      let one = object.methodOne()
+      let two = object.methodTwo()
+      let three = {
+          let a = 1
+          let b = 2
+          let c = 3
+      }()
+      """
+    )
+  }
 }