optional-deps.md

handling optional dependencies failures

If optional dependencies fail to install, we should remove the optional dep from the disk, but keep them included in the lockfile. If they are unresolveable, then they should be removed from the idealTree.

Types of failure:

1. Optional dependency metadata failure (404, etc.) optional-dep-missing
2. Optional dependency tgz download failure optional-dep-tgz-missing
3. Optional dependency version not satisfiable optional-dep-enotarget
4. Optional dependency build failure optional-dep-postinstall-fail
5. Optional dependency specifies unsupported engine or platform optional-platform-specification
6. Optional dependency depends on any failure above
   1. optional-metadep-missing
   2. optional-metadep-tgz-missing
   3. optional-metadep-enotarget
   4. optional-metadep-postinstall-fail

These failures can occur in one of three places:

1. buildIdealTree (unresolveable or failed metadata optional dep/meta-dep)

2. reifyNode (failure to download/unpack tgz, engine/platform unsupported)

3. lifecycle scripts

After taking the diff, get the list of modules to remove trashList

Also add the retired folders to the trash list when they're ready to be removed

If a dep fails, and it has optional: true, then we have to find the entry point into the optional tree. Eg, a -> b -OPT-> c -> d, if d fails, then we need to remove c, as well as any dependencies of c that are not depended upon by any modules outside of the set.

• Gather the set of nodes linking into the node that are not optional: true. We know this won't be unbounded, because the node is optional in the first place.

• Add the set of dependencies from that root node that don't have any edgesIn from outside the set.

• Add the nodes in the set to the trashList.