linkcheck: add `HyperlinkCollector.find_url()` (#12213)

Signed-off-by: James Knight <james.d.knight@live.com>
Co-authored-by: Adam Turner <9087854+aa-turner@users.noreply.github.com>

sphinx/builders/linkcheck.py

@@ -178,41 +178,67 @@ class HyperlinkCollector(SphinxPostTransform):
     default_priority = 800
 
     def run(self, **kwargs: Any) -> None:
+        for node in self.document.findall():
+            if uri := self.find_uri(node):
+                self._add_uri(uri, node)
+
+    def find_uri(self, node: nodes.Element) -> str | None:
+        """Find a URI for a given node.
+
+        This call can be used to retrieve a URI from a provided node. If no
+        URI exists for a provided node, this call will return ``None``.
+
+        This method can be useful for extension developers who wish to
+        easily inject hyperlinks into a builder by only needing to override
+        this method.
+
+        :param node: A node class
+        :returns: URI of the node
+        """
+        # reference nodes
+        if isinstance(node, nodes.reference):
+            if 'refuri' in node:
+                return node['refuri']
+
+        # image nodes
+        if isinstance(node, nodes.image):
+            uri = node['candidates'].get('?')
+            if uri and '://' in uri:
+                return uri
+
+        # raw nodes
+        if isinstance(node, nodes.raw):
+            uri = node.get('source')
+            if uri and '://' in uri:
+                return uri
+
+        return None
+
+    def _add_uri(self, uri: str, node: nodes.Element) -> None:
+        """Registers a node's URI into a builder's collection of hyperlinks.
+
+        Provides the ability to register a URI value determined from a node
+        into the linkcheck's builder. URI's processed through this call can
+        be manipulated through a ``linkcheck-process-uri`` event before the
+        builder attempts to validate.
+
+        :param uri: URI to add
+        :param node: A node class where the URI was found
+        """
         builder = cast(CheckExternalLinksBuilder, self.app.builder)
         hyperlinks = builder.hyperlinks
         docname = self.env.docname
 
-        # reference nodes
-        for refnode in self.document.findall(nodes.reference):
-            if 'refuri' in refnode:
-                uri = refnode['refuri']
-                _add_uri(self.app, uri, refnode, hyperlinks, docname)
+        if newuri := self.app.emit_firstresult('linkcheck-process-uri', uri):
+            uri = newuri
 
-        # image nodes
-        for imgnode in self.document.findall(nodes.image):
-            uri = imgnode['candidates'].get('?')
-            if uri and '://' in uri:
-                _add_uri(self.app, uri, imgnode, hyperlinks, docname)
+        try:
+            lineno = get_node_line(node)
+        except ValueError:
+            lineno = -1
 
-        # raw nodes
-        for rawnode in self.document.findall(nodes.raw):
-            uri = rawnode.get('source')
-            if uri and '://' in uri:
-                _add_uri(self.app, uri, rawnode, hyperlinks, docname)
-
-
-def _add_uri(app: Sphinx, uri: str, node: nodes.Element,
-             hyperlinks: dict[str, Hyperlink], docname: str) -> None:
-    if newuri := app.emit_firstresult('linkcheck-process-uri', uri):
-        uri = newuri
-
-    try:
-        lineno = get_node_line(node)
-    except ValueError:
-        lineno = -1
-
-    if uri not in hyperlinks:
-        hyperlinks[uri] = Hyperlink(uri, docname, app.env.doc2path(docname), lineno)
+        if uri not in hyperlinks:
+            hyperlinks[uri] = Hyperlink(uri, docname, self.env.doc2path(docname), lineno)
 
 
 class Hyperlink(NamedTuple):