Fix sdist build for multiple readme files

src/poetry/core/masonry/builders/sdist.py

@@ -14,6 +14,7 @@
 from posixpath import join as pjoin
 from pprint import pformat
 from typing import TYPE_CHECKING
+from typing import Iterable
 from typing import Iterator
 
 from poetry.core.masonry.builders.builder import Builder
@@ -322,17 +323,21 @@ def find_files_to_add(self, exclude_build: bool = False) -> set[BuildIncludeFile
         to_add = super().find_files_to_add(exclude_build)
 
         # add any additional files, starting with all LICENSE files
-        additional_files = set(self._path.glob("LICENSE*"))
+        additional_files: set[Path] = set(self._path.glob("LICENSE*"))
 
         # add script files
         additional_files.update(self.convert_script_files())
 
         # Include project files
         additional_files.add(Path("pyproject.toml"))
 
-        # add readme if it is specified
+        # add readme files if specified
         if "readme" in self._poetry.local_config:
-            additional_files.add(self._poetry.local_config["readme"])
+            readme: str | Iterable[str] = self._poetry.local_config["readme"]
+            if isinstance(readme, str):
+                additional_files.add(Path(readme))
+            else:
+                additional_files.update(Path(r) for r in readme)
 
         for additional_file in additional_files:
             file = BuildIncludeFile(

tests/fixtures/with_readme_files/pyproject.toml

@@ -1,5 +1,5 @@
 [tool.poetry]
-name = "single-python"
+name = "my-package"
 version = "0.1"
 description = "Some description."
 authors = [
@@ -16,4 +16,4 @@ homepage = "https://python-poetry.org/"
 
 
 [tool.poetry.dependencies]
-python = "2.7.15"
+python = "^2.7"

tests/masonry/builders/test_sdist.py

@@ -175,23 +175,37 @@ def test_find_files_to_add() -> None:
     poetry = Factory().create_poetry(project("complete"))
 
     builder = SdistBuilder(poetry)
-    result = [f.relative_to_source_root() for f in builder.find_files_to_add()]
+    result = {f.relative_to_source_root() for f in builder.find_files_to_add()}
+
+    assert result == {
+        Path("LICENSE"),
+        Path("README.rst"),
+        Path("bin/script.sh"),
+        Path("my_package/__init__.py"),
+        Path("my_package/data1/test.json"),
+        Path("my_package/sub_pkg1/__init__.py"),
+        Path("my_package/sub_pkg2/__init__.py"),
+        Path("my_package/sub_pkg2/data2/data.json"),
+        Path("my_package/sub_pkg3/foo.py"),
+        Path("pyproject.toml"),
+    }
 
-    assert sorted(result) == sorted(
-        [
-            Path("LICENSE"),
-            Path("README.rst"),
-            Path("bin/script.sh"),
-            Path("my_package/__init__.py"),
-            Path("my_package/data1/test.json"),
-            Path("my_package/sub_pkg1/__init__.py"),
-            Path("my_package/sub_pkg2/__init__.py"),
-            Path("my_package/sub_pkg2/data2/data.json"),
-            Path("my_package/sub_pkg3/foo.py"),
-            Path("pyproject.toml"),
-        ]
+
+def test_find_files_to_add_with_multiple_readme_files() -> None:
+    poetry = Factory().create_poetry(
+        Path(__file__).parent.parent.parent / "fixtures" / "with_readme_files"
     )
 
+    builder = SdistBuilder(poetry)
+    result = {f.relative_to_source_root() for f in builder.find_files_to_add()}
+
+    assert result == {
+        Path("README-1.rst"),
+        Path("README-2.rst"),
+        Path("my_package/__init__.py"),
+        Path("pyproject.toml"),
+    }
+
 
 def test_make_pkg_info_multi_constraints_dependency() -> None:
     poetry = Factory().create_poetry(