caldav, carddav: redirect on wrong path

it is much more user-friendly to redirect to the correct
principalPath/homeSetPath when possible

carddav/carddav_test.go

@@ -194,6 +194,43 @@ func TestAddressBookDiscovery(t *testing.T) {
 	}
 }
 
+func TestRedirections(t *testing.T) {
+	ctx := context.Background()
+
+	h := Handler{&testBackend{}, ""}
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		ctx := r.Context()
+		ctx = context.WithValue(ctx, currentUserPrincipalKey, "/principal/")
+		ctx = context.WithValue(ctx, homeSetPathKey, "/principal/contacts/")
+		ctx = context.WithValue(ctx, addressBookPathKey, "/principal/contacts/default")
+		r = r.WithContext(ctx)
+		(&h).ServeHTTP(w, r)
+	}))
+	defer ts.Close()
+
+	client, err := NewClient(nil, ts.URL)
+	if err != nil {
+		t.Fatalf("error creating client: %s", err)
+	}
+	hsp, err := client.FindAddressBookHomeSet(ctx, "/must-be-redirected/")
+	if err != nil {
+		t.Fatalf("error finding home set path: %s", err)
+	}
+	if want := "/principal/contacts/"; hsp != want {
+		t.Fatalf("Found home set path '%s', expected '%s'", hsp, want)
+	}
+	abs, err := client.FindAddressBooks(ctx, "/must-be-redirected/again/")
+	if err != nil {
+		t.Fatalf("error finding address books: %s", err)
+	}
+	if len(abs) != 1 {
+		t.Fatalf("Found %d address books, expected 1", len(abs))
+	}
+	if want := "/principal/contacts/default"; abs[0].Path != want {
+		t.Fatalf("Found address book at %s, expected %s", abs[0].Path, want)
+	}
+}
+
 var mkcolRequestBody = `
 <?xml version="1.0" encoding="utf-8" ?>
    <D:mkcol xmlns:D="DAV:"

carddav/server.go

@@ -332,7 +332,7 @@ func (b *backend) HeadGet(w http.ResponseWriter, r *http.Request) error {
 	return nil
 }
 
-func (b *backend) PropFind(r *http.Request, propfind *internal.PropFind, depth internal.Depth) (*internal.MultiStatus, error) {
+func (b *backend) PropFind(w http.ResponseWriter, r *http.Request, propfind *internal.PropFind, depth internal.Depth) error {
 	resType := b.resourceTypeAtPath(r.URL.Path)
 
 	var dataReq AddressDataRequest
@@ -342,86 +342,92 @@ func (b *backend) PropFind(r *http.Request, propfind *internal.PropFind, depth i
 	case resourceTypeRoot:
 		resp, err := b.propFindRoot(r.Context(), propfind)
 		if err != nil {
-			return nil, err
+			return err
 		}
 		resps = append(resps, *resp)
 	case resourceTypeUserPrincipal:
 		principalPath, err := b.Backend.CurrentUserPrincipal(r.Context())
 		if err != nil {
-			return nil, err
+			return err
 		}
 		if r.URL.Path == principalPath {
 			resp, err := b.propFindUserPrincipal(r.Context(), propfind)
 			if err != nil {
-				return nil, err
+				return err
 			}
 			resps = append(resps, *resp)
 			if depth != internal.DepthZero {
 				resp, err := b.propFindHomeSet(r.Context(), propfind)
 				if err != nil {
-					return nil, err
+					return err
 				}
 				resps = append(resps, *resp)
 				if depth == internal.DepthInfinity {
 					resps_, err := b.propFindAllAddressBooks(r.Context(), propfind, true)
 					if err != nil {
-						return nil, err
+						return err
 					}
 					resps = append(resps, resps_...)
 				}
 			}
+		} else {
+			http.Redirect(w, r, principalPath, http.StatusPermanentRedirect) // keep http method
+			return nil
 		}
 	case resourceTypeAddressBookHomeSet:
 		homeSetPath, err := b.Backend.AddressBookHomeSetPath(r.Context())
 		if err != nil {
-			return nil, err
+			return err
 		}
 		if r.URL.Path == homeSetPath {
 			resp, err := b.propFindHomeSet(r.Context(), propfind)
 			if err != nil {
-				return nil, err
+				return err
 			}
 			resps = append(resps, *resp)
 			if depth != internal.DepthZero {
 				recurse := depth == internal.DepthInfinity
 				resps_, err := b.propFindAllAddressBooks(r.Context(), propfind, recurse)
 				if err != nil {
-					return nil, err
+					return err
 				}
 				resps = append(resps, resps_...)
 			}
+		} else {
+			http.Redirect(w, r, homeSetPath, http.StatusPermanentRedirect) // keep http method
+			return nil
 		}
 	case resourceTypeAddressBook:
 		ab, err := b.Backend.GetAddressBook(r.Context(), r.URL.Path)
 		if err != nil {
-			return nil, err
+			return err
 		}
 		resp, err := b.propFindAddressBook(r.Context(), propfind, ab)
 		if err != nil {
-			return nil, err
+			return err
 		}
 		resps = append(resps, *resp)
 		if depth != internal.DepthZero {
 			resps_, err := b.propFindAllAddressObjects(r.Context(), propfind, ab)
 			if err != nil {
-				return nil, err
+				return err
 			}
 			resps = append(resps, resps_...)
 		}
 	case resourceTypeAddressObject:
 		ao, err := b.Backend.GetAddressObject(r.Context(), r.URL.Path, &dataReq)
 		if err != nil {
-			return nil, err
+			return err
 		}
 
 		resp, err := b.propFindAddressObject(r.Context(), propfind, ao)
 		if err != nil {
-			return nil, err
+			return err
 		}
 		resps = append(resps, *resp)
 	}
 
-	return internal.NewMultiStatus(resps...), nil
+	return internal.ServeMultiStatus(w, internal.NewMultiStatus(resps...))
 }
 
 func (b *backend) propFindRoot(ctx context.Context, propfind *internal.PropFind) (*internal.Response, error) {