• 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: macOS Mojave 10.14.6
• Poetry version: 1.1.3
• Link of a Gist with the contents of your pyproject.toml file:

[[tool.poetry.source]]
name = 'foobar'
url = 'http://repository.intranet.foobar.com/artifactory/api/pypi/pypi-virtual/simple'

[build-system]
requires = ["poetry_core>=1.0.0"]
build-backend = "poetry.core.masonry.api"

Issue

In docs we can read:

Any custom repository will have precedence over PyPI.

In the above example, foobar is a proxy repo incl. both internal packages and the public ones from PyPI. Running poetry install should cause a creation of poetry.lock, where all the packages have foobar in their source field. However, it's completely opposite - none of the packages has a source field, which means all of them are downloaded directly from PyPI.

When I add default = true to the above source element, which means PyPI is disabled, everything works properly - generated poetry.lock includes foobar as a source for all packages and installation doesn't break, so it's not a problem with repository itself.

It's especially frustrating when you want to use poetry export (for any reason), because then the final requirements.txt doesn't include neither --index-url nor --extra-index-url (it seems it depends on the actually used sources, not the pyproject.toml content).