Allow for inheritance of devcontainer spec

[benjaminbauer]

Use case

Working on a project that utilizes devcontainer with a team. The preferences wrt to tooling differs among team members (zsh vs fish, vim vs neovim, etc.).

Current solution

make the devcontainer a union of all the requirments. I.e. install all tools, that any developer in the team favors.

Challenges

1. Container will become bloated
2. potential conflicts between requirements

Potential Solution

include property

add an optional property include to thee devcontainer spec. The value is a valid devcontainer file. When defined, the container described in that file will be the base for the focal definition. I.e. I can add my own tools on top of that definition.

Base file: checked in the project repo, contains the project-wide standards (runtime, linting tools, etc.)
extending file: developer preferences, e.g. certain vscode plugins, editors, shells, etc.

Challenges

conflicts between base and extending definition (e.g. different image)

devcontainer extension file

To avoid the complexity of inheritance as above a special extension file format can be defined. This would be a subset of the devcontainer spec. The properties would only be able to append entries to the base file

example:

{
      "parent": "./devcontainer.json"
      "customizations": {
		"vscode": {
			"extensions": [
				"ms-azuretools.vscode-docker"
			]
		}
	}
}

This would add ms-azuretools.vscode-docker to the parent

[Chuxel]

Great suggestion! There's a proposal for this at devcontainers/spec#22. See what you think!

[benjaminbauer]

Exactly the problem that I am raising here. Thanks for the hint!

[Chuxel]

Great! There's even a PR out for it right now in the reference implementation: devcontainers/cli#311

[benjaminbauer]

When working with devcontainers in VS Code (which is probably true for most users), the described use case can be partially solved with:

1. https://code.visualstudio.com/docs/devcontainers/containers#_always-installed-extensions
2. and the analogous setting for features dev.containers.defaultFeatures

What I would like in the same spirit is: microsoft/vscode-dev-containers#1221

Aside of devcontainers/cli#311, this seems to support this use case too: microsoft/vscode-remote-release#3279