refactor: Support fallback method returning multiple identifiers

Issue #11: #11
PR #12: #12
PR mkdocstrings#350: mkdocstrings/mkdocstrings#350

src/mkdocs_autorefs/plugin.py

@@ -10,9 +10,10 @@
 and fixes them using the previously stored identifier-URL mapping.
 """
 
+import contextlib
 import functools
 import logging
-from typing import Callable, Dict, Optional
+from typing import Callable, Dict, Optional, Sequence
 
 from mkdocs.config import Config
 from mkdocs.plugins import BasePlugin
@@ -68,14 +69,14 @@ def register_url(self, identifier: str, url: str):
         self._abs_url_map[identifier] = url
 
     def get_item_url(
-        self, identifier: str, from_url: Optional[str] = None, fallback: Optional[Callable[[str], Optional[str]]] = None
+        self, identifier: str, from_url: Optional[str] = None, fallback: Optional[Callable[[str], Sequence[str]]] = None
     ) -> str:
         """Return a site-relative URL with anchor to the identifier, if it's present anywhere.
 
         Arguments:
             identifier: The anchor (without '#').
             from_url: The URL of the base page, from which we link towards the targeted pages.
-            fallback: An optional function to suggest an alternative anchor to try on failure.
+            fallback: An optional function to suggest alternative anchors to try on failure.
 
         Returns:
             A site-relative URL.
@@ -90,10 +91,12 @@ def get_item_url(
                 return self._abs_url_map[identifier]
 
             if fallback:
-                new_identifier = fallback(identifier)
-                if new_identifier:
-                    return self.get_item_url(new_identifier, from_url)
-
+                new_identifiers = fallback(identifier)
+                for new_identifier in new_identifiers:
+                    with contextlib.suppress(KeyError):
+                        url = self.get_item_url(new_identifier, from_url)
+                        self._url_map[identifier] = url  # update the map to avoid doing all this again
+                        return url
             raise
 
         if from_url is not None:

tests/test_plugin.py

@@ -34,9 +34,14 @@ def test_url_registration_with_fallback():
     plugin.register_anchor(identifier="foo", page="foo1.html")
     plugin.register_url(identifier="bar", url="https://example.org/bar.html")
 
-    assert plugin.get_item_url("baz", fallback=lambda s: "foo") == "foo1.html#foo"
-    assert plugin.get_item_url("baz", fallback=lambda s: "bar") == "https://example.org/bar.html"
+    # URL map will be updated with baz -> foo1.html#foo
+    assert plugin.get_item_url("baz", fallback=lambda s: ("foo",)) == "foo1.html#foo"
+    # as expected, baz is now known as foo1.html#foo
+    assert plugin.get_item_url("baz", fallback=lambda s: ("bar",)) == "foo1.html#foo"
+    # unknown identifiers correctly fallback: qux -> https://example.org/bar.html
+    assert plugin.get_item_url("qux", fallback=lambda s: ("bar",)) == "https://example.org/bar.html"
+
     with pytest.raises(KeyError):
-        plugin.get_item_url("baz", fallback=lambda s: "baaaa")
+        plugin.get_item_url("foobar", fallback=lambda s: ("baaaa",))
     with pytest.raises(KeyError):
-        plugin.get_item_url("baz", fallback=lambda s: None)
+        plugin.get_item_url("foobar", fallback=lambda s: ())