feat(schematics): add migration for karma app check

packages/schematics/migrations/20180321-add-karma-app-check.ts

@@ -0,0 +1,44 @@
+import * as fs from 'fs';
+import * as ts from 'typescript';
+import { getSourceNodes } from '@schematics/angular/utility/ast-utils';
+import { stripIndents } from '@angular-devkit/core/src/utils/literals';
+
+export default {
+  description: 'Add makeSureNoAppIsSelected(); to karma conf',
+  run: async () => {
+    const contents = fs.readFileSync('karma.conf.js').toString();
+    const sourceFile = ts.createSourceFile('karma.conf.js', contents, ts.ScriptTarget.Latest);
+    const nodes = getSourceNodes(sourceFile);
+    const isPresent = nodes
+      .filter(ts.isCallExpression)
+      .filter((callExpr: ts.CallExpression) => ts.isIdentifier(callExpr.expression))
+      .some((callExpr: ts.CallExpression) => {
+        const identifier = callExpr.expression as ts.Identifier;
+        return identifier.escapedText === 'makeSureNoAppIsSelected';
+      });
+    
+    if (isPresent) {
+      return;
+    }
+
+    const snippet = stripIndents`
+      const { makeSureNoAppIsSelected } = require('@nrwl/schematics/src/utils/cli-config-utils');
+      // Nx only supports running unit tests for all apps and libs.
+      makeSureNoAppIsSelected();
+    `;
+
+    const karmaComment = stripIndents`
+      // Karma configuration file, see link for more information
+      // https://karma-runner.github.io/1.0/config/configuration-file.html
+    `;
+
+    let res: string;
+    if (contents.includes(karmaComment)) {
+      res = contents.replace(karmaComment, karmaComment + '\n\n' + snippet);
+    } else {
+      res = snippet + '\n\n' + contents;
+    }
+
+    fs.writeFileSync('karma.conf.js', res);
+  }
+};