Feature Request: Discover build inputs automatically for Go apps based on imports

[alexrudd]

Hello,

I work in quite a large monorepo with many main funcs and shared packages. Figuring out if a Go app needs to be rebuilt is a bit of a pain and generally something I've found most build tools to be missing.

Bazel solves this by creating build files for every package in a repo and explicitly defining the dependencies between these packages (This is automated using Gazelle). I find this to be a bit messy and overly complicated.

It seems like in Bob I would manually list the directories of all module packages that a particular build needs to get this same behaviour?

There are tools that have been created (tainted, gta) that can determine for any package if its dependencies have changed (by crawling all imports). Point such a tool at a main package and it can tell whether that app needs to be rebuilt.

Would native support for such a capability be something that could be considered for Bob? I would imagine it would have to be a special kind of input:

build:
  my app:
    input: |-
      gopackage:cmd/myapp
    cmd: |-
      go build cmd/myapp

[Equanox]

Hi Alex,

it's a very good point you are bringing up. Thanks for pointing out gta, looking into it.

I see that this is very valuable for medium- or big repos like yours. As it's not really practical to update the inputs by hand. Especially if the main files share many libraries.

I have to investigate how to implement native support for tool-supported-gathering-of inputs and the implications on performance. I can already assure that we will have this on our longterm feature list.

Hint: For Go it's also necessary to track files like go.mod and go.sum to assure reproducible builds.

[Equanox]

WIP #346