Validate error path for addDependency() (#197)

[wabain]

Fixes #197, which is caused by undefined being passed to the loader addDependency method when handling errors. A Svelte CompileError doesn't have a file property, but it does have filename, so try either of those and call addDependency with the value if it is a string (and not equal to the path of the top-level resource being loaded).

In addition to updating tests, I've checked manually that error reporting and rebuilding after an error works in a webpack project that had been hitting ERR_INVALID_ARG_TYPE before this patch.

[bfanger]

this statement favors the err.filename value, is that intended?

[wabain]

It wasn't accidental, but it is arbitrary. I don't have a reason to favor either over the other.

[wabain]

Revisiting this, it occurs to me that one obvious reason to prefer err.file is that it maintains the status quo if there's an error value out there which has both properties. I'll push a change to switch the preference.

[basuke]

https://github.com/sveltejs/svelte/blob/dafbdc286eef3de2243088a9a826e6899e20465c/src/compiler/utils/error.ts#L9
The property of CompileError is filename, not file. Checking is good, but I don't think file should be cared.

[wabain]

It's been a while now, but I think I believed other error types were reachable here.

[basuke]

Why isn't this PR merged in? The crash is very annoying. I appreciate this merging-in pretty soon.

[pngwn]

Your potential appreciation of any 'pretty-soon' merging is duly noted. Thank you for informing us.

[basuke]

@pngwn I'm sorry if my comment made you feeling bad but I really do not get the reason why this PR is halting. Are there any issue or something unclear?

FYI: the crash won't happens when I don't use <script lang=ts>. The compilation error will be caught by the other error handler:

svelte-loader/index.js

Lines 87 to 89 in 79111a9

	// wrap error to provide correct
	// context when logging to console
	callback(new Error(`${err.name}: ${err.toString()}`));

[pngwn]

I'm sorry if my comment made you feeling bad but I really do not get the reason why this PR is halting. Are there any issue or something unclear?

No other reason that we are very busy. We'll get around to it as soon as we can.