`poetry check` command validates readme (files must exist) (#7444)

docs/pyproject.md

@@ -114,6 +114,12 @@ The file(s) can be of any format, but if you intend to publish to PyPI keep the
 https://packaging.python.org/en/latest/guides/making-a-pypi-friendly-readme/) in
 mind. README paths are implicitly relative to `pyproject.toml`.
 
+{{% note %}}
+Whether paths are case-sensitive follows platform defaults, but it is recommended to keep cases.
+
+To be specific, you can set `readme = "rEaDmE.mD"` for `README.md` on macOS and Windows, but Linux users can't `poetry install` after cloning your repo. This is because macOS and Windows are case-insensitive and case-preserving.
+{{% /note %}}
+
 The contents of the README file(s) are used to populate the [Description
 field](https://packaging.python.org/en/latest/specifications/core-metadata/#description-optional)
 of your distribution's metadata (similar to `long_description` in setuptools).

src/poetry/console/commands/check.py

 from __future__ import annotations
 
+from typing import TYPE_CHECKING
+
 from cleo.helpers import option
 
 from poetry.console.commands.command import Command
 
 
+if TYPE_CHECKING:
+    from pathlib import Path
+
+
 class CheckCommand(Command):
     name = "check"
     description = (
@@ -23,7 +29,7 @@ class CheckCommand(Command):
         ),
     ]
 
-    def validate_classifiers(
+    def _validate_classifiers(
         self, project_classifiers: set[str]
     ) -> tuple[list[str], list[str]]:
         """Identify unrecognized and deprecated trove classifiers.
@@ -73,6 +79,17 @@ class CheckCommand(Command):
 
         return errors, warnings
 
+    def _validate_readme(self, readme: str | list[str], poetry_file: Path) -> list[str]:
+        """Check existence of referenced readme files"""
+
+        readmes = [readme] if isinstance(readme, str) else readme
+
+        errors = []
+        for name in readmes:
+            if not (poetry_file.parent / name).exists():
+                errors.append(f"Declared README file does not exist: {name}")
+        return errors
+
     def handle(self) -> int:
         from poetry.factory import Factory
         from poetry.pyproject.toml import PyProjectTOML
@@ -84,10 +101,15 @@ class CheckCommand(Command):
 
         # Validate trove classifiers
         project_classifiers = set(config.get("classifiers", []))
-        errors, warnings = self.validate_classifiers(project_classifiers)
+        errors, warnings = self._validate_classifiers(project_classifiers)
         check_result["errors"].extend(errors)
         check_result["warnings"].extend(warnings)
 
+        # Validate readme (files must exist)
+        if "readme" in config:
+            errors = self._validate_readme(config["readme"], poetry_file)
+            check_result["errors"].extend(errors)
+
         # Verify that lock file is consistent
         if self.option("lock") and not self.poetry.locker.is_locked():
             check_result["errors"] += ["poetry.lock was not found."]

tests/console/commands/test_check.py

@@ -81,6 +81,7 @@ def test_check_invalid(
 Error: 'description' is a required property
 Error: Project name (invalid) is same as one of its dependencies
 Error: Unrecognized classifiers: ['Intended Audience :: Clowns'].
+Error: Declared README file does not exist: never/exists.md
 Error: poetry.lock was not found.
 Warning: A wildcard Python dependency is ambiguous.\
  Consider specifying a more explicit one.

tests/fixtures/invalid_pyproject/pyproject.toml

@@ -4,6 +4,7 @@ version = "1.0.0"
 authors = [
     "Foo <foo@bar.com>"
 ]
+readme = "never/exists.md"
 license = "INVALID"
 classifiers = [
     "Environment :: Console",