Current .npmrc will keep keys with not replaced Environment variables. However values are replaced. So it may confuse somebody & has no option to solve this problem

.npmrc example

registry=${NPM_REGISTRY_URL}
//${NPM_REGISTRY_HOST}/:_authToken=${NPM_AUTH_TOKEN}
always-auth=true

With env.vars:

export NPM_REGISTRY_URL=http://my.registry.com/
export NPM_REGISTRY_HOST=my.registry.com
export NPM_AUTH_TOKEN=xxxxxxxxxxxxxxx

NOW it will produce bellow options:

registry=http://my.registry.com/
//${NPM_REGISTRY_HOST}/:_authToken=xxxxxxxxxxxxxxx
always-auth=true

But expected options are:

registry=http://my.registry.com/
//my.registry.com/:_authToken=xxxxxxxxxxxxxxx
always-auth=true

Probably it is expected state & it would be very helpful when it will be merged for private registries which are using CI for publishing npm packages. For example: Then no more "npm login | answer_input $AUTH_TOKEN ... # etc. constructions" are necessary.