test: Allow custom find-links in pip_install_local()

Author: ichard26

tests/lib/__init__.py

@@ -725,13 +725,26 @@ def pip(
     def pip_install_local(
         self,
         *args: StrPath,
+        find_links: StrPath | list[StrPath] = pathlib.Path(DATA_DIR, "packages"),
         **kwargs: Any,
     ) -> TestPipResult:
+        """Invoke pip install without PyPI access. By default, only local
+        packages are included via --find-links."""
+        # Convert find links paths to absolute file: URIs
+        if not isinstance(find_links, list):
+            find_links = [find_links]
+        find_links_args: list[StrPath] = []
+        for folder in find_links:
+            if isinstance(folder, str) and folder.startswith("file:"):
+                find_links_args.extend(("--find-links", folder))
+            else:
+                path = pathlib.Path(folder).resolve()
+                find_links_args.extend(("--find-links", path.as_uri()))
+
         return self.pip(
             "install",
             "--no-index",
-            "--find-links",
-            pathlib.Path(DATA_DIR, "packages").as_uri(),
+            *find_links_args,
             *args,
             **kwargs,
         )