Fix invalid AST printer: add escape characters to single line descriptions

src/main/java/graphql/GraphQLError.java

@@ -39,8 +39,10 @@ public interface GraphQLError extends Serializable {
     ErrorClassification getErrorType();
 
     /**
-     * The graphql spec says that the (optional) path field of any error should be a list
-     * of path entries https://spec.graphql.org/October2021/#sec-Handling-Field-Errors
+     * The graphql spec says that the (optional) path field of any error must be
+     * a list of path entries starting at the root of the response
+     * and ending with the field associated with the error
+     * https://spec.graphql.org/draft/#sec-Errors.Error-Result-Format
      *
      * @return the path in list format
      */

src/main/java/graphql/language/AstPrinter.java

@@ -534,7 +534,7 @@ private String description(Node<?> node) {
         if (description.isMultiLine()) {
             s = "\"\"\"" + (startNewLine ? "" : "\n") + description.getContent() + "\n\"\"\"\n";
         } else {
-            s = "\"" + description.getContent() + "\"\n";
+            s = "\"" + escapeJsonString(description.getContent()) + "\"\n";
         }
         return s;
     }

src/test/groovy/graphql/parser/ParserTest.groovy

@@ -4,6 +4,7 @@ package graphql.parser
 import graphql.language.Argument
 import graphql.language.ArrayValue
 import graphql.language.AstComparator
+import graphql.language.AstPrinter
 import graphql.language.BooleanValue
 import graphql.language.Description
 import graphql.language.Directive
@@ -1151,5 +1152,35 @@ triple3 : """edge cases \\""" "" " \\"" \\" edge cases"""
         document.getDefinitions()[0].getSourceLocation() == SourceLocation.EMPTY
     }
 
+    def "escape characters correctly printed when printing AST"() {
+        given:
+        def src = "\"\\\"\" scalar A"
+
+        def env = newParserEnvironment()
+                .document(src)
+                .parserOptions(
+                        ParserOptions.newParserOptions()
+                                .captureIgnoredChars(true)
+                                .build()
+                )
+                .build()
+
+        when:
+        // Parse the original Document
+        def doc = Parser.parse(env)
+        // Print the AST
+        def printed = AstPrinter.printAst(doc)
+        // Re-parse printed AST
+        def reparsed = Parser.parse(printed)
+
+        then:
+        noExceptionThrown() // The printed AST was re-parsed without exception
+
+        when:
+        def reparsedPrinted = AstPrinter.printAst(reparsed)
+
+        then:
+        reparsedPrinted == printed // Re-parsing and re-printing produces the same result
+    }
 
 }