Support for PEP508

[escaped]

With PEP508 you can limit certain package to a specific platforms, e.g. waitress==1.0.2;platform_system=="Windows" to install waitress only on Windows.

It seem like poetry doesn't support this feature at all or at least i wasn't able to specify the constraint from above. Neither poetry add waitress==1.0.2;platform_system=="Windows" nor writing waitress = "=1.0.2;platform_system=Windows" to the pyproject.toml works.

[sdispater]

Thanks for your interest in Poetry!

As of now, neither the add command nor the pyproject.toml support PEP 508 when specifying dependencies. And while the pyproject.toml might support it in the future, the add command will most likely not.

The reason for it is that PEP 508 is not really readable when you have markers:

waitress==1.0.2;platform_system="Windows"

is, in my opinion, less readable than:

waitress = { version = "1.0.2", system = "Windows" }  # pyproject.tml

or for the add command:

poetry add waitress=1.0.2 --system Windows

Note that this is not yet supported but this is an idea of what one might expect in a near future for Poetry.

[escaped]

Hey @sdispater,

i wonder why you closed this issue. I checked the recent release and could not find anything related to this issue except for extras, which does not include plattform specific identifiers. I still think it would be really nice to automatically decide whether a required dependency should be installed. Examples for such packages would be:

• pyinotify, which works only on linux
• enum34, which is required for python <3.4

[jacebrowning]

I would use this for pync, which only works on macOS.

And I agree that { version = "*", system = "macOS" } is much more readable that what it would need to map to for PEP508 (sys_platform="darwin").

[sdispater]

The sys_platform constraint is supported by writing your dependency like this:

my-dependency = { version: "*",  "platform": "darwin"}

Note, however, that due to a bug it will be lost if/when packaging/publishing your project. This will likely be fixed in the 0.10.0 release.

[jacebrowning]

With 0.10.0-alpha.1, this line in pyproject.toml:

pync = { version = '*', platform = 'darwin' }

causes this error with $ poetry lock:

[InvalidProjectFile]
[dev-dependencies.pync] {'version': '*', 'platform': 'darwin'} is not valid under any of the given schemas

[sdispater]

@jacebrowning It should be fixed in the latest 0.10.0a2 prerelease.

[github-actions]

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