Merge pull request #1067 from DougGregor/string-literal-expr-escape-newlines

Author: DougGregor

Sources/SwiftSyntaxBuilder/ConvenienceInitializers.swift

@@ -192,6 +192,28 @@ extension MemberAccessExpr {
 
 // MARK: - StringLiteralExpr
 
+extension String {
+  /// Replace literal newlines with "\r", "\n".
+  fileprivate func replacingNewlines() -> String {
+    var result = ""
+    var input = self[...]
+    while let firstNewline = input.firstIndex(where: { $0.isNewline }) {
+      result += input[..<firstNewline]
+      if input[firstNewline] == "\r" {
+        result += "\\r"
+      } else if input[firstNewline] == "\r\n" {
+        result += "\\r\\n"
+      } else {
+        result += "\\n"
+      }
+      input = input[input.index(after: firstNewline)...]
+      continue
+    }
+
+    return result + input
+  }
+}
+
 extension StringLiteralExpr {
   private enum PoundState {
     case afterQuote, afterBackslash, none
@@ -241,7 +263,7 @@ extension StringLiteralExpr {
     closeQuote: Token = .stringQuote,
     closeDelimiter: Token? = nil
   ) {
-    let contentToken = Token.stringSegment(content)
+    let contentToken = Token.stringSegment(content.replacingNewlines())
     let segment = StringSegment(content: contentToken)
     let segments = StringLiteralSegments([.stringSegment(segment)])
 

Sources/_SwiftSyntaxMacros/MacroSystem+Examples.swift

@@ -33,7 +33,7 @@ struct StringifyMacro: ExpressionMacro {
       return MacroResult(ExprSyntax(macro))
     }
 
-    return MacroResult("(\(argument), #\"\(argument)\"#)")
+    return MacroResult("(\(argument), \(StringLiteralExprSyntax(content: argument.description)))")
   }
 }
 

Tests/SwiftSyntaxBuilderTest/StringLiteralTests.swift

@@ -82,4 +82,11 @@ final class StringLiteralTests: XCTestCase {
     #"\"#
     """##)
   }
+
+  func testNewlines() {
+    AssertBuildResult(
+      StringLiteralExpr(content: "linux\nwindows\r\na"),
+      #""linux\nwindows\r\na""#
+    )
+  }
 }

Tests/SwiftSyntaxMacrosTest/MacroSystemTests.swift

@@ -38,13 +38,39 @@ final class MacroSystemTests: XCTestCase {
       """
       1
       let a = (2)
-      let b = (x + y, #"x + y"#)
+      let b = (x + y, "x + y")
       .init(_colorLiteralRed: 0.5, green: 0.5, blue: 0.25, alpha: 1.0)
       let c = 9
       """
     )
   }
 
+  func testStringifyExpression() {
+    let sf: SourceFileSyntax =
+      """
+      _ = #stringify({ () -> Bool in
+        print("hello")
+        return true
+      })
+      """
+    let converter = SourceLocationConverter(file: "test.swift", tree: sf)
+    let context = MacroEvaluationContext(
+      moduleName: "MyModule", sourceLocationConverter: converter
+    )
+    let transformedSF = MacroSystem.exampleSystem.evaluateMacros(
+      node: sf, in: context, errorHandler: { error in }
+    )
+    AssertStringsEqualWithDiff(
+      transformedSF.description,
+      """
+      _ = ({ () -> Bool in
+        print("hello")
+        return true
+      }, #"{ () -> Bool in\\n  print("hello")\\n  return true\\n}"#)
+      """
+    )
+  }
+
   func testPoundFunctionExpansion() {
     let sf: SourceFileSyntax =
       """