Don't special case single argument and don't use to separate arguments

Author: Adrian Zgorzalek

src/language/__tests__/printer-test.js

@@ -60,7 +60,9 @@ describe('Printer: Query document', () => {
       'query ($foo: TestType) @testDirective { id, name }',
     );
     expect(print(queryAstWithArtifacts)).to.equal(dedent`
-      query ($foo: TestType) @testDirective {
+      query (
+        $foo: TestType
+      ) @testDirective {
         id
         name
       }
@@ -70,7 +72,9 @@ describe('Printer: Query document', () => {
       'mutation ($foo: TestType) @testDirective { id, name }',
     );
     expect(print(mutationAstWithArtifacts)).to.equal(dedent`
-      mutation ($foo: TestType) @testDirective {
+      mutation (
+        $foo: TestType
+      ) @testDirective {
         id
         name
       }
@@ -82,7 +86,9 @@ describe('Printer: Query document', () => {
       'query ($foo: TestType = {a: 123} @testDirective(if: true) @test) { id }',
     );
     expect(print(queryAstWithVariableDirective)).to.equal(dedent`
-      query ($foo: TestType = {a: 123} @testDirective(if: true) @test) {
+      query (
+        $foo: TestType = {a: 123} @testDirective(if: true) @test
+      ) {
         id
       }
     `);
@@ -96,7 +102,9 @@ describe('Printer: Query document', () => {
       },
     );
     expect(print(queryAstWithVariableDirective)).to.equal(dedent`
-      fragment Foo($foo: TestType @test) on TestType @testDirective {
+      fragment Foo(
+        $foo: TestType @test
+      ) on TestType @testDirective {
         id
       }
     `);
@@ -157,24 +165,16 @@ describe('Printer: Query document', () => {
         fragment Foo($a: ComplexType, $b: Boolean = false) on TestType {
           id
         }
-
-        fragment Simple($a: Boolean = true) on TestType {
-          id
-        }
       `,
       { experimentalFragmentVariables: true },
     );
     expect(print(fragmentWithVariable)).to.equal(dedent`
       fragment Foo(
-        $a: ComplexType,
+        $a: ComplexType
         $b: Boolean = false
       ) on TestType {
         id
       }
-
-      fragment Simple($a: Boolean = true) on TestType {
-        id
-      }
     `);
   });
 
@@ -186,7 +186,7 @@ describe('Printer: Query document', () => {
     expect(printed).to.equal(
       dedent(String.raw`
       query queryName(
-        $foo: ComplexType,
+        $foo: ComplexType
         $site: Site = MOBILE
       ) @onQuery {
         whoever123is: node(id: [123, 456]) {
@@ -217,7 +217,9 @@ describe('Printer: Query document', () => {
         }
       }
 
-      subscription StoryLikeSubscription($input: StoryLikeSubscribeInput) @onSubscription {
+      subscription StoryLikeSubscription(
+        $input: StoryLikeSubscribeInput
+      ) @onSubscription {
         storyLikeSubscribe(input: $input) {
           story {
             likers {

src/language/printer.js

@@ -285,15 +285,11 @@ function printBlockString(value, isDescription) {
 }
 
 /**
- * Prints variables one per line with a trailing comma, when there is more
- * than one argument. Otherwise print inline.
+ * Prints variables one per line.
  */
 function printVariableDefinitions(args) {
   if (!args || args.length === 0) {
     return '';
   }
-  if (args.length === 1) {
-    return '(' + args[0] + ')';
-  }
-  return '(\n' + indent(join(args, ',\n')) + '\n)';
+  return '(\n' + indent(join(args, '\n')) + '\n)';
 }