Validate the names of directory children, and normalize output directory/file names

[stuhood]

Problem

As explained in #10802 (comment), Pants does not currently normalize Process::{output_files,output_directories} as relative paths, which caused us to send an invalid path to the server. Additionally, the server managed to return a "nearly valid" output where a child path for a directory had an empty name, which we should validate for in order to fail faster.

Solution

In two commits: 1) validate that Directory protos returned by remoting do not contain empty child names, 2) switch the Process::{output_files,output_directories} fields to holding RelativePaths, which are normalized to strip trailing slashes, and validated as not escaping their root.

Result

Fixes #10802. Opened bazelbuild/remote-apis#175 to track upstreaming the additional "must be non-empty" constraint.

[ci skip-build-wheels]

[stuhood]

Commits are useful to review independently.

[tdyas]

So probably no need for my short-term fix in #10849 then?

[stuhood]

So probably no need for my short-term fix in #10849 then?

Happy to land both of them. Yours is likely to go green first, but this change will normalize that path in the Process definition.

[Eric-Arellano]

Thanks! Good call to use RelativePath.

[tdyas]

lgtm. I ran the example-python reproduction of the bug with this change and issue is fixed.

[tdyas]

So probably no need for my short-term fix in #10849 then?

Happy to land both of them. Yours is likely to go green first, but this change will normalize that path in the Process definition.

Good to land both. This will ensure normalization while my change will ensure no need to normalize in that spot.

[coveralls]

Coverage remained the same at 0.0% when pulling 438f390 on stuhood:stuhood/verify-and-normalize-names into 703a509 on pantsbuild:master.