check for error earlier in matchingWalker.Walk to avoid nil deref

[mslynch]

Intent

Related to #3180.

When deploying in this situation, it results in an internal server error due to a nil pointer dereference. We're not checking the error we get from walking the filesystem soon enough.

Type of Change

• • Bug Fix
• • New Feature
• • Breaking Change
• • Documentation
• • Refactor
• • Tooling

Approach

Moved the error handling up so it can catch this case.

User Impact

Users won't hit an internal server error in this case; the filesystem walk will complete successfully and an error will be logged about the file that caused an error.

Automated Tests

Added a test to verify this case.

Directions for Reviewers

Use steps in linked ticket and hit deploy.

Checklist

• I have updated the root CHANGELOG.md to cover notable changes.

[marcosnav]

Moving up the error checking is a good move, although not sure this is the complete solution.

I tried this out and a dir with permissions 600 that is selected in the files tree is still included in the bundle as an empty dir.

There's a UX problem here too. If there are files in the configuration file for which the directory permissions change, it is not possible to de-select from the files tree since the dir won't expand. This is a very contrived issue and maybe not worth solving the UX side of it, specially if we manage to not include the directory on the deployment, which sounds like a good enough solution.