[FEATURE] make affected.defaultBase configurable in nx.json

[ktfleming]

Describe the feature

Right now affected.defaultBase in the generated nx.json is hardcoded to mainline:

https://github.com/aws/aws-prototyping-sdk/blob/4881808bdccb2f3e53df5fc96acc186612634bed/packages/nx-monorepo/src/nx-monorepo.ts#L300-L302

It would be nice if this could be configured in the projen config file.

Use Case

When not using a mainline branch, some nx commands will fail. For example, npx nx print-affected fails with

Error: Command failed: git merge-base --fork-point "mainline" "HEAD"
fatal: No such ref: 'mainline'

Proposed Solution

The branch could be specified as a new parameter in the projen file, or it could be set to options.defaultReleaseBranch (I'm new to nx and not sure which is more appropriate).

Other Information

No response

Acknowledgements

• [ ] I may be able to implement this feature request
• [ ] This feature might incur a breaking change

PDK version used

v0.11.1

What languages will this feature affect?

No response

Environment details (OS name and version, etc.)

Mac OS 12.3.1

[cogwirrel]

Hey, thanks for the feature request!

I can definitely see it being useful to set the affected branch :) defaultReleaseBranch could be a good candidate, though it could also be added to the nxConfig option so it's colocated with other NX options. I'll discuss with dimecha@ when he's back!

As a workaround you can actually customise your nx.json (or other projen managed files) prior to the call to synth(). For example:

const monorepo = new NxMonorepoProject({
  ...
});

monorepo.tryFindObjectFile('nx.json')!.addOverride('affected.defaultBase', 'my-branch');

monorepo.synth();

Hope that helps!

Thanks, Jack