build(docs-infra): make tsconfig path detection in switch-to-ivy mo…

…re robust (angular#29989)

In light of angular#29926, that will change the path of `tsconfig.app.json`,
this commit switches from a hard-coded `tsconfig.app.json` path to
looking it up in `angular.json` (to be more future-proof).

PR Close angular#29989

aio/scripts/switch-to-ivy.js

@@ -10,7 +10,7 @@ set('-e');
 
 // Constants
 const ROOT_DIR = resolve(__dirname, '..');
-const TS_CONFIG_PATH = join(ROOT_DIR, 'src/tsconfig.app.json');
+const NG_JSON = join(ROOT_DIR, 'angular.json');
 const NG_COMPILER_OPTS = {
   angularCompilerOptions: {
     // Related Jira issue: FW-737
@@ -24,14 +24,18 @@ _main(process.argv.slice(2));
 
 // Functions - Definitions
 function _main() {
+  // Detect path to `tsconfig.app.json`.
+  const ngConfig = parse(readFileSync(NG_JSON, 'utf8'));
+  const tsConfigPath = join(ROOT_DIR, ngConfig.projects.site.architect.build.options.tsConfig);
+
   // Enable Ivy in TS config.
-  console.log(`\nModifying \`${TS_CONFIG_PATH}\`...`);
-  const oldTsConfigStr = readFileSync(TS_CONFIG_PATH, 'utf8');
+  console.log(`\nModifying \`${tsConfigPath}\`...`);
+  const oldTsConfigStr = readFileSync(tsConfigPath, 'utf8');
   const oldTsConfigObj = parse(oldTsConfigStr);
   const newTsConfigObj = extend(true, oldTsConfigObj, NG_COMPILER_OPTS);
   const newTsConfigStr = JSON.stringify(newTsConfigObj, null, 2);
   console.log(`\nNew config: ${newTsConfigStr}`);
-  writeFileSync(TS_CONFIG_PATH, newTsConfigStr);
+  writeFileSync(tsConfigPath, newTsConfigStr);
 
   // Run ngcc.
   const ngccArgs = '--loglevel debug --properties es2015 module';
@@ -41,5 +45,5 @@ function _main() {
   // Done.
   console.log('\nReady to build with Ivy!');
   console.log('(To switch back to ViewEngine (with packages from npm), undo the changes in ' +
-              `\`${TS_CONFIG_PATH}\` and run \`yarn aio-use-npm && yarn example-use-npm\`.)`);
+              `\`${tsConfigPath}\` and run \`yarn aio-use-npm && yarn example-use-npm\`.)`);
 }