Inline nullable in flow generics (#1426)

src/printer.js

@@ -1852,7 +1852,9 @@ function genericPrintNoParens(path, options, print, args) {
     case "TypeParameterDeclaration":
     case "TypeParameterInstantiation": {
       const shouldInline =
-        n.params.length === 1 && n.params[0].type === "ObjectTypeAnnotation";
+        n.params.length === 1 &&
+        (n.params[0].type === "ObjectTypeAnnotation" ||
+          n.params[0].type === "NullableTypeAnnotation");
 
       if (shouldInline) {
         return concat(["<", join(", ", path.map(print, "params")), ">"]);

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

@@ -54,6 +54,52 @@ var X = {
 
 `;
 
+exports[`nullable.js 1`] = `
+function formatEntireFile(
+  fileVersion: FileVersion,
+  range: atom$Range,
+): Promise<?{
+  newCursor?: number,
+  formatted: string,
+}> {}
+
+function foo(): Promise<?boolean> {}
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+function formatEntireFile(
+  fileVersion: FileVersion,
+  range: atom$Range
+): Promise<?{
+  newCursor?: number,
+  formatted: string
+}> {}
+
+function foo(): Promise<?boolean> {}
+
+`;
+
+exports[`nullable.js 2`] = `
+function formatEntireFile(
+  fileVersion: FileVersion,
+  range: atom$Range,
+): Promise<?{
+  newCursor?: number,
+  formatted: string,
+}> {}
+
+function foo(): Promise<?boolean> {}
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+function formatEntireFile(
+  fileVersion: FileVersion,
+  range: atom$Range,
+): Promise<?{
+  newCursor?: number,
+  formatted: string,
+}> {}
+
+function foo(): Promise<?boolean> {}
+
+`;
+
 exports[`trailing.js 1`] = `
 type State = {
   errors: Immutable.Map<

tests/flow_generic/jsfmt.spec.js

@@ -1,2 +1,2 @@
-run_spec(__dirname);
-run_spec(__dirname, { trailingComma: 'all' });
+run_spec(__dirname, null, ["babylon"]);
+run_spec(__dirname, { trailingComma: 'all' }, ["babylon"]);

tests/flow_generic/nullable.js

@@ -0,0 +1,9 @@
+function formatEntireFile(
+  fileVersion: FileVersion,
+  range: atom$Range,
+): Promise<?{
+  newCursor?: number,
+  formatted: string,
+}> {}
+
+function foo(): Promise<?boolean> {}