Creating an alias for the node_modules cache doesn't regard the correct checksum


I noticed an interesting bug when using aliases with our new CircleCI 2.0 config:

I set an alias

        node_cache_key: &node_cache_key
        npm-{{ checksum "package.json" }}

This is part of the job:

           - restore_cache:
               key: *node_cache_key
           - run: npm install
           - save_cache:
               key: *node_cache_key
                   - node_modules

And when it would try to recover the cache from previous builds

No cache is found for key: npm-hcMXzcM5ob9jB8+PrSdqJNcMF3MwZ1YrS0RAfe4Zghg=

And then later saving the new cache

Skipping cache generation, cache already exists for key: npm-dH_AZxhZiD+Hh8VLfIJGHMIa4Uh+sbJCwZSUWbG1RaI=
Found one created at 2018-09-05 05:26:30 +0000 UTC0000 UTC

I went ahead and removed the alias and set the commands to just directly reference npm-{{ checksum "package.json" }} and voila, the cache was recognized, and :tada: speedy builds.

I’m not sure if it has something to do with where the checkout step happens (after the alias is created).