inlineDynamicImports: true and moduleSideEffects: 'no-treeshake' causes a hard-to-diagnose error

[lemonmade]

• Rollup Version: 2.49.0
• Operating System (or Browser): macOS 11.3.1
• Node Version (if applicable):
• Link to reproduction (IMPORTANT, read below): https://replit.com/@lemonmade/rollup-tree-shaking-error-reproduction (repo version: https://github.com/lemonmade/rollup-treeshaking-issue)

Expected Behavior

I can set inlineDynamicImports: true, and resolve a module with moduleSideEffects: 'no-treeshake', and have the build complete without an error (in the example, removing moduleSideEffects or inlineDynamicImports both work, and neither changes the output, but my real project requires both to be enabled).

Actual Behavior

The following error is thrown:

[!] TypeError: Cannot read property 'suggestedVariableName' of undefined
TypeError: Cannot read property 'suggestedVariableName' of undefined
    at Object.deconflictImportsOther (/home/runner/rollup-repro/node_modules/rollup/dist/shared/rollup.js:11071:80)
    at deconflictChunk (/home/runner/rollup-repro/node_modules/rollup/dist/shared/rollup.js:11038:52)
    at Chunk.setIdentifierRenderResolutions (/home/runner/rollup-repro/node_modules/rollup/dist/shared/rollup.js:12323:9)
    at Chunk.preRender (/home/runner/rollup-repro/node_modules/rollup/dist/shared/rollup.js:11707:14)
    at Bundle.prerenderChunks (/home/runner/rollup-repro/node_modules/rollup/dist/shared/rollup.js:13027:19)
    at Bundle.generate (/home/runner/rollup-repro/node_modules/rollup/dist/shared/rollup.js:12892:18)
    at processTicksAndRejections (internal/process/task_queues.js:97:5)
    at async handleGenerateWrite (/home/runner/rollup-repro/node_modules/rollup/dist/shared/rollup.js:20623:23)
    at async Promise.all (index 0)
    at async build (/home/runner/rollup-repro/node_modules/rollup/dist/bin/rollup:1533:5)

I tracked this down a little bit, and noticed that we add the offending undefineds in

rollup/src/utils/getStaticDependencies.ts

Lines 42 to 46 in d73b2ac

	const dependencyChunk = chunkByModule.get(dependency)!;
	if (dependencyChunk !== chunk) {
	staticDependencies.push(dependencyChunk);
	continue;
	}

. Interestingly, the module that gets added here (e.g., has chunkByModule.get(dependency) == null) was always an index file that just re-exports other parts of the module being imported (I used a library from my real example, @remote-ui/core, but it was not specific to this library in my larger example).

Thanks in advance for your help, and for the amazing work on Rollup!

[lukastaegert]

Thanks for spotting, fix at #4104

[lemonmade]

@lukastaegert Thank you so much for the quick fix!