• I am on the latest Poetry version.
• I have searched the issues of this repo and believe that this is not a duplicate.
• If an exception occurs when executing a command, I executed it again in debug mode (-vvv option).

• OS version and name: Ubuntu 18.04
• Poetry version: 1.0.0a5
• Link of a Gist with the contents of your pyproject.toml file: mimal example inline below

Issue

Background

I use the extras section to describe additional clusters of packages, as documented in the readme:

# ~~ snip ~~

[tool.poetry.dependencies]
attrs = "~=19.1"
black = { version = "==18.9b0", optional = true }

[tool.poetry.extras]
lint = ["black"]

When I run poetry install, only attrs is installed, and when I run poetry install --extras lint, both attrs and black are installed. So far this is all expected behaviour.

Issue

When I run poetry export -f requirements.txt, all main packages are exported, including all optional packages.

I would expect that the default output of export excludes optional packages, and that these have to be added by an --extras flag.

I'm happy to write up a PR for this, should be something by the end of today.