fix: CompilerHost.getSourceFile is being called for odd filenames

[alan-agius4]

Would love to add some Unit Tests but kinda can't find a way where to test it. If any one is willing to give me pointers on how do you guy usually test this. I'll happily add them

Ignore falsy file names from getSourceFileFromReferenceWorker

Closes: #13629

[mhegazy]

@alan-agius4 we will need a unit test to go with this change. i would say you need a new file, since we do not have any existing unit test files that cover this area.
you can look at https://github.com/Microsoft/TypeScript/blob/master/src/harness/unittests/hostNewLineSupport.ts for reference for testing compilerHost use.

[alan-agius4]

@mhegazy, thanks for the example, that was helpful.

I added the some tests.

[mhegazy]

how about doing this check on the call to getDefaultLibraryFileName instead. it is making me a bit nervous to have it in this general utility function, just to handle the return of getDefaultLibraryFileName.

[alan-agius4]

Making you nervous is not a good sign.

You mean here: https://github.com/alan-agius4/TypeScript/blob/a27cd8f9a2e83d4b6fbf4e77c5041d94b01d86f6/src/compiler/program.ts#L611

Change it to something like

   const defaultLibraryFileName = getDefaultLibraryFileName();
                if (!options.lib && defaultLibraryFileName) {
                    processRootFile(defaultLibraryFileName, /*isDefaultLib*/ true);
                }

Ps: I make the change already, and if you are not too convinced about this. I don't mind closing the PR, just leave a comment in the original issue :)

[mhegazy]

thanks. this seems much targeted now. sorry for the back and forth.