TypeError: Cannot read property 'specifier' of undefined, instead of "A module cannot import itself"

[coni2k]

When using "rollup" with a combination with a module that is trying to import itself (in my case "breeze-client"), it cannot reach to "A module cannot import itself" error message and fails with "TypeError: Cannot read property 'specifier' of undefined" error message.

It happens in the following block, at return declaration.source === source line:

if ( resolvedId === module.id ) {
	// need to find the actual import declaration, so we can provide
	// a useful error message. Bit hoop-jumpy but what can you do
	var name = Object.keys( module.imports )
		.find( function (name) {
			var declaration = module.imports[ name ];
			return declaration.source === source;
		});

	var declaration = module.imports[ name ].specifier.parent;

	module.error({
		code: 'CANNOT_IMPORT_SELF',
		message: "A module cannot import itself"
	}, declaration.start );
}

And the values of these variables:
declaration.source: commonjs-proxy:breeze-client
source: breeze-client

This leads to name variable becoming null (or undefined?) and then next line fails with "TypeError: Cannot read property 'specifier' of undefined" error message:

var declaration = module.imports[ name ].specifier.parent;

I have created a small demo app that shows the error. I tried to make the app as simple as possible, however I saw your "Issue Guideline" after preparing the application, and unfortunately it still contains typescript and gulp steps to show you the error.

I already spent some time to prepare this demo app but if you think it's still too much, I can even try to make it simpler.

https://github.com/forCrowd/Labs-RollupJS-InvalidAliasesFix

• Download node packages
• Compile typescript files
• Run the the following gulp tasks to see each case:
• build-invalidSettings-buggy: Uses invalid settings (no alias defined for "breeze-client". Rollup should show "A module cannot import itself" error message, but cannot due to "TypeError: Cannot read property 'specifier' of undefined" error.
• build-invalidSettings-fixed: Again uses invalid settings, but experimentally fixed version of rollup and now rollup shows the correct error message.
• build-valid: This tasks is here just to show that rollup works as expected with the correct settings.

Experimental fix that I did is simply changing this line:

return declaration.source === source;

to this:

return declaration.source.endsWith(source);

Also the actual error message can be improved by mentioning the module name like this?:

message: "A module cannot import itself: " + source

Probably this is not correct way of fixing this error but in case if you think it's fine for the moment, I can send you a pull request.

Stack trace

TypeError: Cannot read property 'specifier' of undefined at ...\node_modules\rollup\dist\rollup.js:9557:47

[noamichael]

I had this exact same issue in my project - thank you ding finding this!

[ariporad]

Same here, this was causing me problems. Thanks so much!

[GordonSmith]

Me three..

[Rich-Harris]

Fixed in 0.42 — thanks all