fix(@ngtools/webpack): rebuilding project with errors reports cannot find .ts files in JIT

When the first build in JIT has an error we are not emitting files. This ends up causing an issue because subsequent builds only trigger partial emits of files and only emits the full set of files if the number of files changed is greater than 20.

This logic adds the behavior that we only enter the 'only 20 files' part when the previous build was successful.

Fixes #14644

Author: Alan

packages/angular_devkit/build_angular/test/browser/rebuild_spec_large.ts

@@ -9,7 +9,7 @@
 
 import { Architect } from '@angular-devkit/architect';
 import { TestLogger } from '@angular-devkit/architect/testing';
-import { normalize, virtualFs } from '@angular-devkit/core';
+import { logging, normalize, virtualFs } from '@angular-devkit/core';
 import { debounceTime, take, takeWhile, tap } from 'rxjs/operators';
 import { createArchitect, host, lazyModuleFiles, lazyModuleStringImport } from '../utils';
 
@@ -68,14 +68,11 @@ describe('Browser Builder rebuilds', () => {
 
     const overrides = { watch: true };
 
-    let buildCount = 0;
     let phase = 1;
     const run = await architect.scheduleTarget(target, overrides);
     await run.output.pipe(
       tap(result => {
         expect(result.success).toBe(true, 'build should succeed');
-        buildCount++;
-
         const hasLazyChunk = host.scopedSync().exists(normalize('dist/lazy-lazy-module.js'));
         switch (phase) {
           case 1:
@@ -205,6 +202,47 @@ describe('Browser Builder rebuilds', () => {
     ).toPromise();
   });
 
+  it('rebuilds after errors in JIT', async () => {
+    const origContent = virtualFs.fileBufferToString(
+      host.scopedSync().read(normalize('src/app/app.component.ts')));
+    host.appendToFile('./src/app/app.component.ts', `console.logg('error')`);
+
+    const overrides = { watch: true, aot: false };
+    let buildNumber = 0;
+    const logger = new logging.Logger('');
+    let logs: string[] = [];
+    logger.subscribe(e => logs.push(e.message));
+
+    const run = await architect.scheduleTarget(target, overrides, { logger });
+    await run.output.pipe(
+      debounceTime(1000),
+      tap((buildEvent) => {
+        buildNumber ++;
+        switch (buildNumber) {
+          case 1:
+            // The first build should error out with an error.
+            expect(buildEvent.success).toBe(false);
+            expect(logs.join()).toContain(`Property 'logg' does not exist on type 'Console'`);
+            logs = [];
+            // Fix the error.
+            host.writeMultipleFiles({ 'src/app/app.component.ts': `
+              ${origContent}
+              console.errorr('error');
+            `});
+            break;
+
+          case 2:
+            // The second build should have everything fixed.
+            expect(buildEvent.success).toBe(true);
+            expect(logs.join()).not.toContain('Module build failed');
+            break;
+        }
+      }),
+      take(2),
+    ).toPromise();
+    await run.stop();
+  });
+
   it('rebuilds after errors in AOT', async () => {
     // Save the original contents of `./src/app/app.component.ts`.
     const origContent = virtualFs.fileBufferToString(

packages/ngtools/webpack/src/angular_compiler_plugin.ts

@@ -1196,7 +1196,7 @@ export class AngularCompilerPlugin {
           'AngularCompilerPlugin._emit.ts', diagMode));
 
         if (!hasErrors(allDiagnostics)) {
-          if (this._firstRun || changedTsFiles.size > 20) {
+          if (this._firstRun || changedTsFiles.size > 20 || this._emitSkipped) {
             emitResult = tsProgram.emit(
               undefined,
               undefined,