AngularJS module loading error: missing dependency during bootstrap

Answer the exact question first

AngularJS will not start if any module listed in an angular.module dependency array has not been registered beforehand. There is no built‑in configuration to skip or defer a missing module, and this behavior is identical across minor releases (1.6, 1.7, 1.8). A custom bootstrap wrapper can catch the error and log a graceful message, but the application will still not be fully functional until the missing module is supplied.

Likely explanation

• The script that defines missingModule is either not included, is loaded after the main app script, or fails to execute due to an earlier error.
• Using async or defer on the module script can cause it to load after angular.bootstrap() or ng-app, triggering the injector error.
• If a module loader (RequireJS, SystemJS, etc.) is used, the loader may not be configured to expose the Angular module to the global namespace before bootstrap.

Steps to fix the error in this case

1. Verify script order: In the HTML, ensure the missingModule.js file appears before the file that creates the main app module or before the ng-app directive is processed.

   <script src="missingModule.js"></script>
   <script src="app.js"></script>

2. Check module name spelling: The dependency array must match the registered name exactly, including case.

   angular.module('app', ['missingModule']); // must match angular.module('missingModule', []);

3. Avoid async/defer on Angular modules unless the loader guarantees execution before bootstrap.

   <script src="missingModule.js" defer></script> 
   

4. For loader‑based projects, configure the loader to load the dependency first or shim it:

   require.config({
     shim: { 'missingModule': { deps: ['angular'] } }
   });

5. Test load order by adding a console.log('missingModule loaded'); at the top of the module file and checking the console before the bootstrap error appears.

Answers to your specific questions

1. Any documented pattern to skip or defer missing modules? No. AngularJS requires all dependencies to be registered before bootstrap; there is no fallback mechanism or configuration flag to ignore a missing module.
2. Differences between 1.6 and 1.8 on missing module handling? The injector error message and bootstrap behavior are consistent across these minor releases. Neither version introduced a graceful degradation path for missing modules.
3. Can a custom bootstrap trap provide graceful degradation? Yes, you can wrap angular.bootstrap() in a try/catch block or listen for the error event on angular.element(document) to log a user‑friendly message. However, the application will still lack the functionality that the missing module would have provided; the error cannot be silently ignored.

Ask for missing diagnostic detail (if needed)

If you are using a module loader or a build tool that bundles scripts, confirm whether the build output includes the missingModule file and that it is executed before the main app script. This detail can change the recommendation on whether to adjust the loader configuration or to add a shim.