Feature Dependencies - installsAfter not respected

[virtualstaticvoid]

Hello,

I've written a couple of features for a project I'm working on and I've ran into situations where I'm not sure what the best approach to take is.

For example, I have a feature which involves installing a CLI tool using npm. Now, I'm not sure whether this feature should also install Node.js so that it is able to install the CLI tool, since I have no control over the base image, nor the included features in the devcontainer.json file.

The power of features, as I understand, is that they can be composed together; making each serve one purpose (installing the given feature) thus providing a simple way to handle all the tooling permutations for many different developers and/or teams whilst avoiding "golden container images"; and similar perhaps in concept to buildpacks.

So it occurred to me that since devcontainers/features already provide features for installing Node.js (and other language runtimes), it would be beneficial to make my feature dependant on the node feature. Then I wouldn't need to worry about which base image a developer is using, and the node feature would be automatically included before mine, so my feature would install reliably.

Additional scenarios include:

• a Ruby gem which needs to build a native extension and thus requires build-essential to be installed.
• a Python package, installed via pip, needing to ensure Python and pip are installed.
• a Go CLI tool, which doesn't have a binary distribution, installed using go install, needing go to be installed.
• a tflint ruleset for AWS, which requires Terraform and tflint to be installed.

I realise installing packages using a postCreateCommand script can work, but it places the onus on the developer to know what features to include to install the given package. For example, I'm building features which install Python packages (e.g. mkdocs) for C# .Net developers, who wouldn't know to include the python feature.

I imagine a devcontainer-feature.json file including a dependsOn property, in the same schema as the devcontainer.json features object.

I.e.

"dependsOn": {
  "ghcr.io/user/repo/go": {},
  "ghcr.io/user/repo1/go:1": {},
  "ghcr.io/user/repo2/go:latest": {},
  "https://github.com/user/repo/releases/devcontainer-feature-go.tgz": { 
        "optionA": "value" 
  },
  "./myGoFeature": { 
        "optionA": true,
        "optionB": "hello",
        "version" : "1.0.0"
  }
}

[joshspicer]

Thank you for your insights. The extend in which we want to incorporate some notion of loose/strong dependencies (if any) has been a topic of discussion for a while now. This is a valuable perspective.

The reference implementation and proposed spec provides an installsAfter attribute that can be added to a feature's devcontainer-feature.json.

installsAfter is an array of ID’s of Features that should execute before this one. Allows control for feature authors on soft dependencies between different Features

[virtualstaticvoid]

Ah, I wasn't aware of the installsAfter feature. Not sure how I missed that.

Thanks for the reply!

[joshspicer]

Please feel free to update us on whether installsAfter works for your use case. We would love the feedback (good and bad!)

[virtualstaticvoid]

Will do. I do have further feedback, related to installations into the user's home directory and also secrets, but I'll raise those with separate issues.

[virtualstaticvoid]

Has installsAfter been implemented in cli?.

I updated my feature JSON and it doesn't seem to work as expected.

Surprisingly, a search of Github for installsAfter contains very few results; and without any code which suggests it is implemented.

[joshspicer]

Yep, looks like a small typo after some refactoring. We'll be pushing changes shortly, and then afterwards please let us know your feedback :)

[Chuxel]

Transferred issue to CLI repo since this is a bug verses a spec change at the moment.