fix: support editable install with multiple roots

Python packages may have multiple root modules where
each is installed to its own folder under `site-packages`.

When using new setuptools editable install in such cases
griffe, when used by mkdocstrings fails to find the
correct paths.

The root cause it that griffe assumed a variable named
`MAPPING` in the `.py` file created by the editable install,
and assumed that this variable is a dict with single entry.

When a package has multiple roots - then this dictionary
contain multiple entries.

This PR aims to handle such cases.

I have no knowledge about `editables` so I could not fix
that case.

The unit test added simulates the case, and this has been tested
against a real complex package with multiple roots using setuptools
65 editable install.

src/griffe/finder.py

@@ -2,6 +2,7 @@
 
 from __future__ import annotations
 
+import ast
 import os
 import re
 import sys
@@ -268,8 +269,12 @@ def _extend_from_editable_modules(self):
         for path in self.search_paths:  # noqa: WPS440
             for item in self._contents(path):
                 if item.stem.startswith(("__editables_", "__editable__")) and item.suffix == ".py":
-                    with suppress(UnhandledEditableModuleError):
-                        self._append_search_path(_handle_editable_module(item))
+                    self._extend_from_an_editable_module(item)
+
+    def _extend_from_an_editable_module(self, item: Path):
+        with suppress(UnhandledEditableModuleError):
+            for editable_path in _handle_editable_module(item):
+                self._append_search_path(editable_path)
 
     def _filter_py_modules(self, path: Path) -> Iterator[Path]:
         for root, dirs, files in os.walk(path, topdown=True):
@@ -338,22 +343,21 @@ def _handle_editable_module(path: Path):  # noqa: WPS231
         editable_lines = path.read_text(encoding="utf8").splitlines(keepends=False)
     except FileNotFoundError:
         raise UnhandledEditableModuleError(path)
+
     if path.name.startswith("__editables_"):
         # support for how 'editables' writes these files:
         # example line: F.map_module('griffe', '/media/data/dev/griffe/src/griffe/__init__.py')
         new_path = Path(editable_lines[-1].split("'")[3])
         if new_path.exists():  # TODO: could remove existence check
             if new_path.name.startswith("__init__"):
-                return new_path.parent.parent
-            return new_path
+                return [new_path.parent.parent]
+            return [new_path]
     elif path.name.startswith("__editable__"):
         # support for how 'setuptools' writes these files:
-        # example line: MAPPING = {'griffe': '/media/data/dev/griffe/src/griffe'}
+        # example line: MAPPING = {'griffe': '/media/data/dev/griffe/src/griffe', 'briffe': '/media/data/dev/griffe/src/briffe'}
         for line in editable_lines:
-            match = _re_mapping_line.match(line)
-            if match:
-                new_path = Path(match.group(1))
-                if new_path.exists():  # TODO: could remove existence check
-                    return new_path.parent
-                break
+            if line.startswith("MAPPING"):
+                paths = ast.literal_eval(line.split(" = ", 1)[1])
+                assert isinstance(paths, dict)
+                return [Path(pt).parent for pt in paths.values()]
     raise UnhandledEditableModuleError(path)

tests/test_finder.py

@@ -94,7 +94,7 @@ def test_editables_file_handling(tmp_path):
     """
     pth_file = tmp_path / "__editables_whatever.py"
     pth_file.write_text("hello\nF.map_module('griffe', 'src/griffe/__init__.py')")
-    assert _handle_editable_module(pth_file) == Path("src")
+    assert list(_handle_editable_module(pth_file)) == [Path("src")]
 
 
 def test_setuptools_file_handling(tmp_path):
@@ -105,4 +105,15 @@ def test_setuptools_file_handling(tmp_path):
     """
     pth_file = tmp_path / "__editable__whatever.py"
     pth_file.write_text("hello\nMAPPING = {'griffe': 'src/griffe'}")
-    assert _handle_editable_module(pth_file) == Path("src")
+    assert list(_handle_editable_module(pth_file)) == [Path("src")]
+
+
+def test_setuptools_file_handling_multiple_paths(tmp_path):
+    """Assert editable modules by `setuptools` are handled when multiple packages are installed in the same editable.
+
+    Parameters:
+        tmp_path: Pytest fixture.
+    """
+    pth_file = tmp_path / "__editable__whatever.py"
+    pth_file.write_text("hello\nMAPPING = {'griffe': 'src1/griffe', 'briffe':'src2/briffe'}")
+    assert list(_handle_editable_module(pth_file)) == [Path("src1"), Path("src2")]