How can I specify differing sets of dependency extras for each of my project's extras?

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Question

How can I specify differing sets of dependency extras for each of my project’s extras? This is something that is relatively trivial to do with setup.py. To clarify, I would like to be able to specify the following dependency graph:

myproject[feature-a] depends on [dependency-one, dependency-two[feature-a]] myproject[feature-b] depends on [dependency-one, dependency-two[feature-b]]

I’ll propose a couple ways that pyproject.toml might model these graphs, but the core value of these examples is to highlight an apparent deficiency with the current model.

1. By allowing dependency aliases that specify distinct sets of extras. For example:

[tool.poetry.dependencies]
…
dependency-two-a = { git = "git+ssh://[e-mail]/projects/dependency-two.git",optional = true,extras = ["feature-a"], provides="dependency-two" }
dependency-two-b = { git = "git+ssh://[e-mail]/projects/dependency-two.git",optional = true,extras = ["feature-b"], provides="dependency-two" }
…

[tool.poetry.extras]
feature-a = ["dependency-one", "dependency-two-a"]
feature-b = ["dependency-one", "dependency-two-b"]

1. By treating the set of extras in the dependencies section as a superset that can be further filtered down when the dependency is referenced in the extras section. For example:

[tool.poetry.dependencies]
…
dependency-two = { git = "git+ssh://[e-mail]/projects/dependency-two.git",optional = true,extras = ["feature-a", "feature-b"]}
…

[tool.poetry.extras]
feature-a = ["dependency-one", "dependency-two[feature-a]"]
feature-b = ["dependency-one", "dependency-two[feature-b]"]

Thanks for your time!

[micuda]

Thanks for creating this issue, @kurtiss. We have the same problem. I would prefer option (2) proposed by @kurtiss, because it feels more intuitive - this was the first thing I tried.

What do you think, @sdispater?

@wshayes you are describing a different use-case here.

[blaise17]

I have a subtly different use case, which I’m not sure works with the currently proposed solutions without some modification. Specifically, I need the dependency without extras to not be optional, but the dependency with extras to be optional. I also need one or more of the extras for the dependency to not be optional, while one or more still are optional. Would it be possible to specify the optional flag per extra?

For example:

[tool.poetry.dependencies]
…
dependency-one = {version = "^1.2.0", extras = [{extra="feature-a", optional = true}, "feature-b"] }
dependency-two = {version = "^1.2.0", extras = [{extra="feature-a", optional = true}] }
…

[tool.poetry.extras]
feature-a = ["dependency-one[feature-a]", "dependency-two[feature-a]"]