refactor(@schematics/angular): add readIntoSourceFile

Author: JLHwung

packages/schematics/angular/component/index.ts

@@ -30,6 +30,14 @@ import { parseName } from '../utility/parse-name';
 import { validateHtmlSelector, validateName } from '../utility/validation';
 import { Schema as ComponentOptions } from './schema';
 
+function readIntoSourceFile(host: Tree, modulePath: string): ts.SourceFile {
+  const text = host.read(modulePath);
+  if (text === null) {
+    throw new SchematicsException(`File ${modulePath} does not exist.`);
+  }
+  const sourceText = text.toString('utf-8');
+  return ts.createSourceFile(modulePath, sourceText, ts.ScriptTarget.Latest, true);
+}
 
 function addDeclarationToNgModule(options: ComponentOptions): Rule {
   return (host: Tree) => {
@@ -38,12 +46,7 @@ function addDeclarationToNgModule(options: ComponentOptions): Rule {
     }
 
     const modulePath = options.module;
-    const text = host.read(modulePath);
-    if (text === null) {
-      throw new SchematicsException(`File ${modulePath} does not exist.`);
-    }
-    const sourceText = text.toString('utf-8');
-    const source = ts.createSourceFile(modulePath, sourceText, ts.ScriptTarget.Latest, true);
+    const source = readIntoSourceFile(host, modulePath);
 
     const componentPath = `/${options.path}/`
                           + (options.flat ? '' : strings.dasherize(options.name) + '/')
@@ -66,12 +69,7 @@ function addDeclarationToNgModule(options: ComponentOptions): Rule {
 
     if (options.export) {
       // Need to refresh the AST because we overwrote the file in the host.
-      const text = host.read(modulePath);
-      if (text === null) {
-        throw new SchematicsException(`File ${modulePath} does not exist.`);
-      }
-      const sourceText = text.toString('utf-8');
-      const source = ts.createSourceFile(modulePath, sourceText, ts.ScriptTarget.Latest, true);
+      const source = readIntoSourceFile(host, modulePath);
 
       const exportRecorder = host.beginUpdate(modulePath);
       const exportChanges = addExportToModule(source, modulePath,
@@ -88,12 +86,7 @@ function addDeclarationToNgModule(options: ComponentOptions): Rule {
 
     if (options.entryComponent) {
       // Need to refresh the AST because we overwrote the file in the host.
-      const text = host.read(modulePath);
-      if (text === null) {
-        throw new SchematicsException(`File ${modulePath} does not exist.`);
-      }
-      const sourceText = text.toString('utf-8');
-      const source = ts.createSourceFile(modulePath, sourceText, ts.ScriptTarget.Latest, true);
+      const source = readIntoSourceFile(host, modulePath);
 
       const entryComponentRecorder = host.beginUpdate(modulePath);
       const entryComponentChanges = addEntryComponentToModule(source, modulePath,