Improve error message for packages in src folder

src/poetry/core/factory.py

@@ -12,6 +12,7 @@
 from packaging.utils import canonicalize_name
 
 from poetry.core.utils.helpers import combine_unicode
+from poetry.core.utils.helpers import module_name
 from poetry.core.utils.helpers import readme_content_type
 
 
@@ -50,6 +51,10 @@ def create_poetry(
 
         # Checking validity
         check_result = self.validate(pyproject.data)
+        src_check_results = self.validate_project_in_src(pyproject.data, cwd)
+        check_result["errors"].extend(src_check_results["errors"])
+        check_result["warnings"].extend(src_check_results["warnings"])
+
         if check_result["errors"]:
             message = ""
             for error in check_result["errors"]:
@@ -582,6 +587,47 @@ def validate(
 
         return result
 
+    @classmethod
+    def validate_project_in_src(
+        cls, toml_data: dict[str, Any], base_path: Path | None
+    ) -> dict[str, list[str]]:
+        """
+        Checks the validity of projects located under src/ subdirectory.
+        """
+        result: dict[str, list[str]] = {"errors": [], "warnings": []}
+
+        project_name = toml_data.get("project", {}).get("name") or toml_data.get(
+            "tool", {}
+        ).get("poetry", {}).get("name")
+
+        if project_name is None or base_path is None:
+            return result
+
+        project_name = module_name(project_name)
+
+        project_dir = base_path / project_name
+        src_project_dir = base_path / "src" / project_name
+
+        project_dir_empty = (
+            project_dir.exists()
+            and project_dir.is_dir()
+            and not any(project_dir.iterdir())
+        )
+        src_dir_not_empty = (
+            src_project_dir.exists()
+            and src_project_dir.is_dir()
+            and any(src_project_dir.iterdir())
+        )
+
+        if project_dir_empty and src_dir_not_empty:
+            result["warnings"].append(
+                f"Found empty directory '{project_name}' in project root while the actual package is in "
+                f"'src/{project_name}'. This may cause issues with package installation. "
+                "Consider removing the empty directory."
+            )
+
+        return result
+
     @classmethod
     def _validate_legacy_vs_project(
         cls, toml_data: dict[str, Any], result: dict[str, list[str]]

tests/fixtures/project_with_src_folder/pyproject.toml

@@ -0,0 +1,9 @@
+[tool.poetry]
+name = "project-with-src-folder"
+version = "1.2.3"
+description = "This is a description"
+authors = ["Your Name <[email protected]>"]
+license = "MIT"
+
+[tool.poetry.dependencies]
+python = "*"

tests/test_factory.py

@@ -533,6 +533,25 @@ def test_create_poetry_empty_readme(tmp_path: Path) -> None:
     assert not poetry.package.readmes
 
 
+def test_create_poetry_src_folder(tmp_path: Path) -> None:
+    cwd = fixtures_dir / "project_with_src_folder"
+
+    (cwd / "project_with_src_folder").mkdir(exist_ok=True)
+
+    pyproject = cwd / "pyproject.toml"
+    with pyproject.open("rb") as f:
+        content = tomllib.load(f)
+
+    assert Factory.validate_project_in_src(content, cwd) == {
+        "errors": [],
+        "warnings": [
+            "Found empty directory 'project_with_src_folder' in project root while the actual package is in "
+            "'src/project_with_src_folder'. This may cause issues with package installation. "
+            "Consider removing the empty directory."
+        ],
+    }
+
+
 def test_validate() -> None:
     complete = fixtures_dir / "complete.toml"
     with complete.open("rb") as f: