Normalize GraphQL multi-line strings (#3632)

* Normalize GraphQL multi-line strings

See discussion in https://github.com/prettier/prettier/pull/3605#discussion_r159120321

* split

src/language-graphql/printer-graphql.js

@@ -126,9 +126,13 @@ function genericPrint(path, options, print) {
     }
     case "StringValue": {
       if (n.block) {
-        // It is not possible to distinguish between """\nabc\n""" and """abc"""
+        return concat([
-        // https://github.com/graphql/graphql-js/issues/1188
+          '"""',
-        return options.originalText.slice(util.locStart(n), util.locEnd(n));
+          hardline,
+          join(hardline, n.value.replace(/"""/g, "\\$&").split("\n")),
+          hardline,
+          '"""'
+        ]);
       }
       return concat(['"', n.value.replace(/["\\]/g, "\\$&"), '"']);
     }
@@ -274,6 +278,8 @@ function genericPrint(path, options, print) {
 
     case "FieldDefinition": {
       return concat([
+        path.call(print, "description"),
+        n.description ? hardline : "",
         path.call(print, "name"),
         n.arguments.length > 0
           ? group(

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

@@ -110,9 +110,12 @@ fragment frag on Friend {
   foo(
     size: $size
     bar: $b
-    obj: { key: "value", block: """
+    obj: {
+      key: "value"
+      block: """
       block string uses \\"""
-  """ }
+      """
+    }
   )
 }
 

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

@@ -14,12 +14,29 @@ abc
 type T {
   a: Int
 }
+
+"""
+  a
+    b
+      c
+         """
+type T { a: Int }
+
+type Foo {
+"""
+This is a description
+of the \`one\` field.
+"""
+  one: Type
+}
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 query X($a: Int) @relay(meta: "{\\"lowPri\\": true}") {
   a
 }
 
-"""abc"""
+"""
+abc
+"""
 type T {
   a: Int
 }
@@ -31,4 +48,21 @@ type T {
   a: Int
 }
 
+"""
+a
+  b
+    c
+"""
+type T {
+  a: Int
+}
+
+type Foo {
+  """
+  This is a description
+  of the \`one\` field.
+  """
+  one: Type
+}
+
 `;

tests/graphql_string/string.graphql

@@ -11,3 +11,18 @@ abc
 type T {
   a: Int
 }
+
+"""
+  a
+    b
+      c
+         """
+type T { a: Int }
+
+type Foo {
+"""
+This is a description
+of the `one` field.
+"""
+  one: Type
+}