optional=true not respected for local `file` dependency, but works with local `path` dependency

Description

Here's a really small reproducible test:

First, grab a .whl to depend on. For simplicity, I'm using six because it has no dependencies:

$ wget https://www.piwheels.org/simple/six/six-1.17.0-py2.py3-none-any.whl#sha256=cb514bebb7be30e172d571b0e5035990437dd202f3c9f6e911d9406254151b92

Now, make a pyproject.toml like this:

[tool.poetry]
name = "test-optional"
version = "0.0.1"

[tool.poetry.dependencies]
python = "^3.9"
six = {optional = true, file = "six-1.17.0-py2.py3-none-any.whl"}

[tool.poetry.extras]
myextra = ["six"]

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

Now generate the lock file:

$ ~/.local/bin/poetry lock
Updating dependencies
Resolving dependencies... (0.1s)

Writing lock file

Note there was no warning or error. Now look at the lock file and see that six is not considered optional:

$ cat poetry.lock
# This file is automatically @generated by Poetry 2.1.3 and should not be changed by hand.

[[package]]
name = "six"
version = "1.17.0"
description = "Python 2 and 3 compatibility utilities"
optional = false
python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*"
groups = ["main"]
markers = "extra == \"myextra\""
files = [
    {file = "six-1.17.0-py2.py3-none-any.whl", hash = "sha256:cb514bebb7be30e172d571b0e5035990437dd202f3c9f6e911d9406254151b92"},
]

[package.source]
type = "file"
url = "six-1.17.0-py2.py3-none-any.whl"

[extras]
myextra = ["six"]

[metadata]
lock-version = "2.1"
python-versions = "^3.9"
content-hash = "3453e3714689a598766b5adad5524b8718b1cc55dc17b28c63922df187265330"

Note that it contains optional = false, which is an error.

Workarounds

If the pyproject.toml file uses path instead of file, everything works:

[tool.poetry]
name = "test-optional"
version = "0.0.1"

[tool.poetry.dependencies]
python = "^3.9"
six = {optional = true, path = "six-1.17.0-py2.py3-none-any.whl"}

[tool.poetry.extras]
myextra = ["six"]

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

$ ~/.local/bin/poetry lock
Resolving dependencies... (0.1s)

Writing lock file

$ cat poetry.lock 
# This file is automatically @generated by Poetry 2.1.3 and should not be changed by hand.

[[package]]
name = "six"
version = "1.17.0"
description = "Python 2 and 3 compatibility utilities"
optional = true
python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*"
groups = ["main"]
markers = "extra == \"myextra\""
files = [
    {file = "six-1.17.0-py2.py3-none-any.whl", hash = "sha256:cb514bebb7be30e172d571b0e5035990437dd202f3c9f6e911d9406254151b92"},
]

[package.source]
type = "file"
url = "six-1.17.0-py2.py3-none-any.whl"

[extras]
myextra = ["six"]

[metadata]
lock-version = "2.1"
python-versions = "^3.9"
content-hash = "a7c28ec18952f6253307197c341fbf63ce14c757acdc3d1481b70335e1c1ff06"

Poetry Installation Method

install.python-poetry.org

Operating System

Ubuntu

Poetry Version

Poetry (version 2.1.3)

Poetry Configuration

cache-dir = "/home/chucky/.cache/pypoetry"
data-dir = "/home/chucky/.local/share/pypoetry"
installer.max-workers = null
installer.no-binary = null
installer.only-binary = null
installer.parallel = true
installer.re-resolve = true
keyring.enabled = true
python.installation-dir = "{data-dir}/python"  # /home/chucky/.local/share/pypoetry/python
requests.max-retries = 0
solver.lazy-wheel = true
system-git-client = false
virtualenvs.create = true
virtualenvs.in-project = null
virtualenvs.options.always-copy = false
virtualenvs.options.no-pip = false
virtualenvs.options.system-site-packages = false
virtualenvs.path = "{cache-dir}/virtualenvs"  # /home/chucky/.cache/pypoetry/virtualenvs
virtualenvs.prompt = "{project_name}-py{python_version}"
virtualenvs.use-poetry-python = false

Python Sysconfig

Platform: "linux-x86_64"
Python version: "3.12"

Example pyproject.toml

[tool.poetry]
name = "test-optional"
version = "0.0.1"

[tool.poetry.dependencies]
python = "^3.9"
six = {optional = true, file = "six-1.17.0-py2.py3-none-any.whl"}

[tool.poetry.extras]
myextra = ["six"]

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

Poetry Runtime Logs

$ ~/.local/bin/poetry lock -vvv
...
Resolving dependencies...
 1: fact: test-optional is 0.0.1
 1: derived: test-optional
 1: fact: test-optional depends on six (*)
 1: selecting test-optional (0.0.1)
 1: derived: six (*) @ file:///home/chucky/poetry-bug/six-1.17.0-py2.py3-none-any.whl
 1: selecting six (1.17.0 /home/chucky/poetry-bug/six-1.17.0-py2.py3-none-any.whl)
 1: Version solving took 0.003 seconds.
 1: Tried 1 solutions.

Reproduce the issue with the provided pyproject.toml using poetry lock, then compare the generated poetry.lock for file and path dependencies. Trace the dependency-resolution and lock-generation entry points responsible for the optional flag. Done means the file dependency records optional = true consistently with the path dependency, with regression coverage for the reported configuration.