Use default redirect when nothing matches.

tests/test_handler.py

@@ -40,10 +40,10 @@ def test_redirect_with_mime_match(self, urihandler):
     def test_redirect_with_mime_no_match(self, urihandler):
         req = testing.DummyRequest(accept="application/pdf")
         req.host_url = "http://test.urihandler.org"
-        with pytest.raises(HTTPNotAcceptable):
-            urihandler.handle("http://test.urihandler.org/foobar/18", req)
+        res = urihandler.handle("http://test.urihandler.org/foobar/18", req)
+        assert res == "http://localhost:5555/foobar/18"
 
-    def test_redirect_default_mime(self, urihandler):
+    def test_redirect_default_set(self, urihandler):
         req = testing.DummyRequest()
         req.host_url = "http://test.urihandler.org"
         res = urihandler.handle("http://test.urihandler.org/pdf_default/18", req)
@@ -54,12 +54,17 @@ def test_redirect_default_mime(self, urihandler):
         res = urihandler.handle("http://test.urihandler.org/pdf_default/18", req)
         assert res == "http://localhost:5555/pdf_default/18.json"
 
-    def test_redirect_no_default_mime(self, urihandler):
+    def test_redirect_no_default(self, urihandler):
         req = testing.DummyRequest()
         req.host_url = "http://test.urihandler.org"
         with pytest.raises(HTTPNotAcceptable):
             urihandler.handle("http://test.urihandler.org/mime_no_default/18", req)
 
+        req = testing.DummyRequest(accept="application/pdf")
+        req.host_url = "http://test.urihandler.org"
+        with pytest.raises(HTTPNotAcceptable):
+            urihandler.handle("http://test.urihandler.org/mime_no_default/18", req)
+
     def test_unanchored_redirect(self, urihandler):
         req = testing.DummyRequest()
         req.host_url = "http://test.urihandler.org"

urihandler/handler.py

@@ -34,22 +34,39 @@ def handle(self, uri, request):
             if m:
                 redirect = u["redirect"]
                 if isinstance(redirect, dict):
-                    if isinstance(request.accept, AcceptNoHeader):
-                        redirect = redirect.get("default")
-                        if not redirect:
-                            raise HTTPNotAcceptable()
-                    else:
-                        for mime, redirect in redirect.items():
-                            if mime in request.accept:
-                                break
-                        else:
-                            # No matching mime was found.
-                            raise HTTPNotAcceptable()
+                    redirect = self._get_redirect_based_on_accept_header(
+                        request.accept, redirect
+                    )
                 redirect = redirect.format(**m.groupdict())
                 log.debug(f"Match found. Redirecting to {redirect}.")
                 return redirect
         return None
 
+    def _get_redirect_based_on_accept_header(self, accept_header, redirect_rule):
+        """
+        Return the redirect rule based on accept header.
+
+        At its core it simply looks for a matching mime between accept header
+        and the configured mime type redirects. But exceptions apply.
+
+        If there is no accept header specified or if no matching mime is found,
+        the default will be returned. If default is not set, HTTP 406 gets raised.
+        """
+        default = redirect_rule.get("default")
+        if isinstance(accept_header, AcceptNoHeader):
+            if not default:
+                raise HTTPNotAcceptable()
+            return default
+
+        for mime, redirect in redirect_rule.items():
+            if mime in accept_header:
+                return redirect
+
+        if not default:
+            raise HTTPNotAcceptable()
+
+        return default
+
 
 def _build_uri_handler(registry, handlerconfig):
     """