Relationship between cache and store and offline "update"

[Chardrazle]

When working with offline modes for some commands, a fully populated cache seems mandatory.
Is there some reason to this? In other words, wouldn't the store contain the required packages anyway?

As a demonstration:

mkdir /tmp/pnpm_test
cd /tmp/pnpm_test
pnpm add @types/react  # Arbitrary package
# This^ might be the state for a while, then at some later point the cache might be removed, say a different user's development env.
# We can simulate this by using:
pnpm cache delete
# Now try an offline update:
pnpm update --offline
 ERR_PNPM_NO_OFFLINE_META  Failed to resolve @types/react@>=19.0.1 <20.0.0-0 in package mirror <...>/.cache/pnpm/metadata-v1.3/registry.npmjs.org/@types/react.json

If we then try adding the package back:

pnpm add @types/react 
Already up to date
pnpm update --offline
 ERR_PNPM_NO_OFFLINE_META  Failed to resolve @types/react@>=19.0.1 <20.0.0-0 in package mirror /home/richard/.cache/pnpm/metadata-v1.3/registry.npmjs.org/@types/react.json

OK, let's try adding direct to the store:

pnpm store add @types/react 
+ @types/[email protected]
pnpm update --offline
 ERR_PNPM_NO_OFFLINE_META  Failed to resolve csstype@>=3.0.2 <4.0.0-0 in package mirror <...>/.cache/pnpm/metadata-v1.3/registry.npmjs.org/csstype.json

That^ actually worked, as it's moved on to the next package. Similarly adding that one (direct to the store) would resolve that error, too.

Is there an explanation for this behaviour?
It seems that restoring files to the "store" also fixes the "cache" (metadata), but it's not obvious in how to achieve that.

[zkochan]

pnpm add @types/react

Did nothing because @types/react was already in the lockfile.

pnpm store add @types/react

This had to download @types/react metadata to resolve the latest version of @types/react.

[Chardrazle]

Thanks for the follow up. That directed me to try understand why our system was getting into a stuck state.
It turns out it’s the permissions on the cache directory.

A simulation:

# A custom cache location is set up by “something else”, with wrong perms, so:
mkdir -p /tmp/pnpm-cache
sudo chown root /tmp/pnpm-cache
pnpm config set cache-dir /tmp/pnpm-cache

# Elsewhere, normal init:
mkdir /tmp/pnpm-perms
cd /tmp/pnpm-perms
pnpm add csstype  # Looks good, !but! the cache dir cannot be updated 
# Then this fails (it would succeed if cache had been updated):
pnpm update --offline

What would be useful here is if pnpm could emit a diagnostic to report that the cache dir could not be updated. The add action is silently progressing (and same for store add).