Error: Tried to overwrite <package_path>.__ivy_ngcc_bak with an ngcc back up file, which is disallowed

Question

I have upgraded from Angular 8 to 9 and have enabled Ivy following all the steps here. When I run npm install a handful of my packages throw the error:

Tried to overwrite <package_path>.__ivy_ngcc_bak with an ngcc back up file, which is disallowed.

What does this mean and why is it happening? I'm having a hard time finding any info on it. I've installed the latest version for all of these packages throwing this error and I still get the error when I run npm install. Thanks!

Answer 1

This is an issue regarding the ivy compiler which is the default compiler from angular 9 onwards (read issue details). you can disable ivy compiler as below to avoid this error.

• Go to tsconfig.json and find angularCompilerOptions.

• Then add below

  "angularCompilerOptions": { "enableIvy": false }

Answer 2

This can happen when you have an ivy-compiled node package and you update the node package's files.

To fix, delete all of the compilation files for the node package (eg. in <package_path>) that have __ivy_ngcc_ in the filename or in the file extension, then restart Angular.