docs: add NG0403.md for Bootstrapped NgModule doesn't specify which c…

…omponent to initialize error (#48483)

- update `errors.ts` to annotate the error NG0403, so that the runtime can add a link to that guide when an error is thrown
- update `application_ref_spec.ts` to include the new link of the error
- update `errors.md` as a result of running `yarn bazel test packages/core/test`

Fixes #47985

PR Close #48483

aio/content/errors/NG0403.md

@@ -0,0 +1,42 @@
+@name Bootstrapped NgModule doesn't specify which component to initialize
+@category runtime
+@shortDescription An NgModule that was used for bootstrapping does not specify which component should be initialized.
+
+@description
+This error means that an NgModule that was used for bootstrapping an application is missing key information for Angular to proceed with the bootstrap process.
+
+The error happens when the NgModule `bootstrap` property is missing (or is an empty array) in the `@NgModule` annotation and there is no `ngDoBootstrap` lifecycle hook defined on that NgModule class.
+
+More information about the bootstrapping process can be found in [this guide](guide/bootstrapping).
+
+The following examples will trigger the error.
+
+```typescript
+@NgModule({
+  declarations: [AppComponent],
+  imports: [BrowserModule, AppRoutingModule],
+  providers: [],
+})
+export class AppModule {}
+
+// The `AppModule` is used for bootstrapping, but the `@NgModule.bootstrap` field is missing.
+platformBrowser().bootstrapModule(AppModule);
+```
+
+```typescript
+@NgModule({
+  declarations: [AppComponent],
+  imports: [BrowserModule, AppRoutingModule],
+  providers: [],
+  bootstrap: [],
+})
+export class AppModule {}
+
+// The `AppModule` is used for bootstrapping, but the `@NgModule.bootstrap` field contains an empty array.
+platformBrowser().bootstrapModule(AppModule);
+```
+
+@debugging
+Please make sure that the NgModule that is used for bootstrapping is setup correctly:
+- either the `bootstrap` property exists (and contains a non-empty array) in the `@NgModule` annotation
+- or the `ngDoBootstrap` method exists on the NgModule class

goldens/public-api/core/errors.md

@@ -21,7 +21,7 @@ export const enum RuntimeErrorCode {
     // (undocumented)
     ASYNC_INITIALIZERS_STILL_RUNNING = 405,
     // (undocumented)
-    BOOTSTRAP_COMPONENTS_NOT_FOUND = 403,
+    BOOTSTRAP_COMPONENTS_NOT_FOUND = -403,
     // (undocumented)
     CYCLIC_DI_DEPENDENCY = -200,
     // (undocumented)

packages/core/src/errors.ts

@@ -53,7 +53,7 @@ export const enum RuntimeErrorCode {
   MULTIPLE_PLATFORMS = 400,
   PLATFORM_NOT_FOUND = 401,
   ERROR_HANDLER_NOT_FOUND = 402,
-  BOOTSTRAP_COMPONENTS_NOT_FOUND = 403,
+  BOOTSTRAP_COMPONENTS_NOT_FOUND = -403,
   PLATFORM_ALREADY_DESTROYED = 404,
   ASYNC_INITIALIZERS_STILL_RUNNING = 405,
   APPLICATION_REF_ALREADY_DESTROYED = 406,

packages/core/test/application_ref_spec.ts

@@ -456,8 +456,10 @@ class SomeComponent {
          waitForAsync(async () => {
            defaultPlatform.bootstrapModule(await createModule({ngDoBootstrap: false}))
                .then(() => expect(false).toBe(true), (e) => {
-                 const expectedErrMsg =
-                     `NG0403: The module MyModule was bootstrapped, but it does not declare "@NgModule.bootstrap" components nor a "ngDoBootstrap" method. Please define one of these.`;
+                 const expectedErrMsg = `NG0403: The module MyModule was bootstrapped, ` +
+                     `but it does not declare "@NgModule.bootstrap" components nor a "ngDoBootstrap" method. ` +
+                     `Please define one of these. ` +
+                     `Find more at https://angular.io/errors/NG0403`;
                  expect(e.message).toEqual(expectedErrMsg);
                  expect(mockConsole.res[0].join('#')).toEqual('ERROR#Error: ' + expectedErrMsg);
                });