[rush] rush build --from does not build transitive dependencies

[mikeharder]

Overview

Consider a dependency graph where B depends on A, and D depends on both B and C:

A <- B <- D
     C <- D

Say I am making changes to B, and want to verify that B and all its downstream dependencies can build correctly. I use the following command:

rush build --to B --from B

Expected

Rush should build all projects downstream of B, including their transitive dependencies (which are required for them to build). D is downstream of B so it must be built, and C is upstream of D so it must also be built.

Actual

Rush does not build C.

Workarounds

Without building the transitive dependencies of downstream projects, the only workaround I see is to build all projects in the monorepo.

Repo

https://github.com/mikeharder/rush-to-from

[iclanton]

Looking into this. So the dependency graph for your repro repo is:

D --> C (not built)
  `--> B --> A

This illustrates a weirdness with the --from parameter, where Rush doesn't ensure the dependencies of projects it's building are built. I think we have two options for addressing this:

• Change the behavior of the --from parameter to also include all other dependencies of projects that are to be built. This will be a breaking change.
• Add the aforementioned behavior with an additional flag (something like --ensure-dependencies-are-built, but with a better name) to avoid making a breaking change.

I'm not sure which approach I prefer, or if there are any additional options.

@octogonz, @apostolisms - thoughts?

[mikeharder]

@iclanton: Thanks for taking a look. I just noticed the title of this issue incorrectly said --to instead of --from (now corrected), but you are correct the issue is with --from not ensuring dependencies are built.

We would be fine with either option (changing --from or additional flag). If one option could be implemented more quickly (say the additional flag since it's a non-breaking change), we would prefer that option.

[octogonz]

@nickpape FYI

[octogonz]

This picture looks exactly correct for rush build --to B --from B:

D --> C (not built)
  `--> B --> A

• --to B means "build B, plus the things that B depends on". That set is { A, B }.
• --from B means "build B, plus all the things that depend on B" That set is { B, D }.

When you specify both parameters, you get the union { A, B, D }.

That union is meaningful and useful. For example, suppose I did a clean clone of the repo, and I made some changes to B. The --to B ensures that I build all the prerequisites for building B. The --from B ensures that I run all the unit tests that could possibly by broken by my change. In this scenario, building C is irrelevant and potentially would waste a lot of time.

[octogonz]

Ohhhh... wait a sec, I get it. The problem is that D fails to build because C wasn't built. Duh. :-P

[octogonz]

Yeah, let's fix this.

[antl3x]

No updates?

[arikon]

What is the progress?

[octogonz]

This will be fixed by PR #2422

[mikeharder]

Closing issue since PR #2422 has been merged