Add error message for missing content-type header

[brandones]

Currently, if the Content-Type header is missing from the response, the error that appears in the console is TypeError: Cannot read property 'match' of null. I'd like to preempt that error with a more helpful one, reusing the existing Error #4.

[joeldenning]

This looks good, and I think it's worth the few extra bytes to help people diagnose issues loading modules. I've added one suggestion

[joeldenning]

If you could add a test for this, that would also be great, too. However, I won't block approval on it.

[joeldenning]

Thanks! I'll plan on merging and publishing tomorrow.

[brandones]

Sorry about the slow response. If you don't mind waiting, I could take a crack at writing a test tomorrow.

It looks like it should go in test/browser/core.js?

[joeldenning]

It looks like it should go in test/browser/core.js?

Yes. Additionally, you'll need to configure the server to omit the content-type header from its response - see

systemjs/test/server.cjs

Lines 12 to 19 in d37f7ca

	const mimes = {
	'.html': 'text/html',
	'.css': 'text/css',
	'.js': 'application/javascript',
	'.mjs': 'application/javascript',
	'.json': 'application/json',
	'.wasm': 'application/wasm'
	};

as a starting point. Perhaps it would make sense to make an exception to those mime types for a specific fixture that you create for this test.

[joeldenning]

The tests look good to me. I'll plan on merging and publishing this in the next day or so.

[joeldenning]

Released in https://github.com/systemjs/systemjs/releases/tag/6.3.3