Fix decorator comments for export class (#2038)

We need to do the same location trick for export class unfortunately.

Fixes #1956

src/util.js

@@ -206,9 +206,18 @@ function hasSpaces(text, index, opts) {
 }
 
 function locStart(node) {
+  // Handle nodes with decorators. They should start at the first decorator
+  if (
+    node.declaration &&
+    node.declaration.decorators &&
+    node.declaration.decorators.length > 0
+  ) {
+    return locStart(node.declaration.decorators[0]);
+  }
   if (node.decorators && node.decorators.length > 0) {
     return locStart(node.decorators[0]);
   }
+
   if (node.range) {
     return node.range[0];
   }

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

@@ -11,6 +11,20 @@ var x = 100
 class X {
 
 }
+
+
+@NgModule({
+  // Imports.
+  imports: [
+    // Angular modules.
+    BrowserModule,
+
+    // App modules.
+    CoreModule,
+    SharedModule,
+  ],
+})
+export class AppModule {}
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 var x = 100;
 
@@ -21,6 +35,19 @@ var x = 100;
 })
 class X {}
 
+@NgModule({
+  // Imports.
+  imports: [
+    // Angular modules.
+    BrowserModule,
+
+    // App modules.
+    CoreModule,
+    SharedModule
+  ]
+})
+export class AppModule {}
+
 `;
 
 exports[`methods.js 1`] = `

tests/decorators/comments.js

@@ -8,3 +8,17 @@ var x = 100
 class X {
 
 }
+
+
+@NgModule({
+  // Imports.
+  imports: [
+    // Angular modules.
+    BrowserModule,
+
+    // App modules.
+    CoreModule,
+    SharedModule,
+  ],
+})
+export class AppModule {}