fix(grahpql): linebreak in non-block stringValue (#4808)

src/language-graphql/printer-graphql.js

@@ -144,7 +144,11 @@ function genericPrint(path, options, print) {
           '"""'
         ]);
       }
-      return concat(['"', n.value.replace(/["\\]/g, "\\$&"), '"']);
+      return concat([
+        '"',
+        n.value.replace(/["\\]/g, "\\$&").replace(/\n/g, "\\n"),
+        '"'
+      ]);
     }
     case "IntValue":
     case "FloatValue":

tests/graphql_string/__snapshots__/jsfmt.spec.js.snap

@@ -49,6 +49,10 @@ Description of \`one\`
 """
 one: string
 }
+
+{
+  foo(input: {multiline: "ab\\ncd"}) { id }
+}
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 query X($a: Int) @relay(meta: "{\\"lowPri\\": true}") {
   a
@@ -113,4 +117,10 @@ input Input {
   one: string
 }
 
+{
+  foo(input: { multiline: "ab\\ncd" }) {
+    id
+  }
+}
+
 `;

tests/graphql_string/string.graphql

@@ -46,3 +46,7 @@ Description of `one`
 """
 one: string
 }
+
+{
+  foo(input: {multiline: "ab\ncd"}) { id }
+}