Support "// swift-format-ignore" for multi-line strings.

Author: thunderseethe

Sources/SwiftFormat/PrettyPrint/TokenStreamCreator.swift

@@ -2446,6 +2446,13 @@ fileprivate final class TokenStreamCreator: SyntaxVisitor {
       if !node.segments.isEmpty {
         before(node.closingQuote, tokens: .break(breakKind, newlines: .hard(count: 1)))
       }
+      if shouldFormatterIgnore(node: Syntax(node)) {
+        appendFormatterIgnored(node: Syntax(node))
+        // Mirror the tokens we'd normally append on '"""'
+        appendTrailingTrivia(node.closingQuote)
+        appendAfterTokensAndTrailingComments(node.closingQuote)
+        return .skipChildren
+      }
     }
     return .visitChildren
   }

Tests/SwiftFormatTests/PrettyPrint/StringTests.swift

@@ -48,6 +48,33 @@ final class StringTests: PrettyPrintTestCase {
       linelength: 30)
   }
 
+  func testMultilineStringIsNotReformattedWithIgnore() {
+    let input =
+      #"""
+      let someString =
+        // swift-format-ignore
+        """
+        lines \
+        are \
+        short.
+        """
+      """#
+
+    let expected =
+      #"""
+      let someString =
+        // swift-format-ignore
+        """
+        lines \
+        are \
+        short.
+        """
+
+      """#
+
+    assertPrettyPrintEqual(input: input, expected: expected, linelength: 30)
+  }
+
   func testMultilineStringWithInterpolations() {
     let input =
         #"""