fix(caldav): use /dav/projects/ as home to make iOS/MacOS reminders work (#2417)

Resolves issue #475 by modifying CalDAV discovery so Apple Reminders can
use /dav/projects/ as the home set without exposing that synthetic path
as a real task list, preserving the existing principal-based flow. This
is because Apple Reminders defaults back to the /dav/projects/ URL,
rather than accepting the /dav/principals/username/ URL specified in
Vikunja.

Resolves #475

pkg/routes/caldav/handler.go

@@ -82,7 +82,7 @@ func ProjectHandler(c *echo.Context) error {
 	log.Debugf("[CALDAV] Request Headers: %v\n", c.Request().Header)
 
 	caldav.SetupStorage(storage)
-	caldav.SetupUser("dav/projects")
+	caldav.SetupUser(strings.TrimPrefix(ProjectHomeSetPath, "/"))
 	caldav.SetupSupportedComponents([]string{lib.VCALENDAR, lib.VTODO})
 	response := caldav.HandleRequest(c.Request())
 	response.Write(c.Response())
@@ -137,7 +137,7 @@ func PrincipalHandler(c *echo.Context) error {
 	log.Debugf("[CALDAV] Request Headers: %v\n", c.Request().Header)
 
 	caldav.SetupStorage(storage)
-	caldav.SetupUser("dav/principals/" + u.Username)
+	caldav.SetupUser(strings.TrimPrefix(principalPathForUser(u.Username), "/"))
 	caldav.SetupSupportedComponents([]string{lib.VCALENDAR, lib.VTODO})
 
 	response := caldav.HandleRequest(c.Request())
@@ -166,7 +166,7 @@ func EntryHandler(c *echo.Context) error {
 	log.Debugf("[CALDAV] Request Headers: %v\n", c.Request().Header)
 
 	caldav.SetupStorage(storage)
-	caldav.SetupUser("dav/principals/" + u.Username)
+	caldav.SetupUser(strings.TrimPrefix(principalPathForUser(u.Username), "/"))
 	caldav.SetupSupportedComponents([]string{lib.VCALENDAR, lib.VTODO})
 
 	response := caldav.HandleRequest(c.Request())

pkg/routes/caldav/listStorageProvider.go

@@ -35,10 +35,16 @@ import (
 )
 
 // DavBasePath is the base url path
-const DavBasePath = `/dav/`
+const DavBasePath = `/dav`
 
 // ProjectBasePath is the base path for all projects resources
-const ProjectBasePath = DavBasePath + `projects`
+const ProjectBasePath = DavBasePath + `/projects`
+
+// PrincipalBasePath is the base path for all principal resources
+const PrincipalBasePath = DavBasePath + `/principals`
+
+// ProjectHomeSetPath is the CalDAV home-set path Apple clients use after discovery.
+const ProjectHomeSetPath = ProjectBasePath + `/`
 
 // VikunjaCaldavProjectStorage represents a project storage
 type VikunjaCaldavProjectStorage struct {
@@ -68,7 +74,7 @@ func (vcls *VikunjaCaldavProjectStorage) GetResources(rpath string, withChildren
 	// and not /dav/projects. I'm not sure if thats a bug in the client or in caldav-go.
 
 	if vcls.isEntry {
-		r := data.NewResource(rpath, &VikunjaProjectResourceAdapter{
+		r := data.NewResource(withTrailingSlash(rpath), &VikunjaProjectResourceAdapter{
 			isPrincipal:  true,
 			isCollection: true,
 		})
@@ -77,7 +83,7 @@ func (vcls *VikunjaCaldavProjectStorage) GetResources(rpath string, withChildren
 
 	// If the request wants the principal url, we'll return that and nothing else
 	if vcls.isPrincipal {
-		r := data.NewResource(DavBasePath+`/projects/`, &VikunjaProjectResourceAdapter{
+		r := data.NewResource(ProjectHomeSetPath, &VikunjaProjectResourceAdapter{
 			isPrincipal:  true,
 			isCollection: true,
 		})
@@ -128,6 +134,14 @@ func (vcls *VikunjaCaldavProjectStorage) GetResources(rpath string, withChildren
 	}
 	projects := theprojects.([]*models.Project)
 
+	if !withChildren {
+		r := data.NewResource(withTrailingSlash(rpath), &VikunjaProjectResourceAdapter{
+			isPrincipal:  true,
+			isCollection: true,
+		})
+		return []data.Resource{r}, nil
+	}
+
 	var resources []data.Resource
 	for _, l := range projects {
 		rr := VikunjaProjectResourceAdapter{
@@ -144,6 +158,20 @@ func (vcls *VikunjaCaldavProjectStorage) GetResources(rpath string, withChildren
 	return resources, nil
 }
 
+func withTrailingSlash(path string) string {
+	if path == "" {
+		return ProjectHomeSetPath
+	}
+	if strings.HasSuffix(path, "/") {
+		return path
+	}
+	return path + "/"
+}
+
+func principalPathForUser(username string) string {
+	return withTrailingSlash(PrincipalBasePath + `/` + username)
+}
+
 // GetResourcesByList fetches a list of resources from a slice of paths
 func (vcls *VikunjaCaldavProjectStorage) GetResourcesByList(rpaths []string) (resources []data.Resource, err error) {
 

pkg/routes/routes.go

@@ -806,6 +806,7 @@ func registerCalDavRoutes(c *echo.Group) {
 	// THIS is the entry point for caldav clients, otherwise projects will show up double
 	c.Any("", caldav.EntryHandler)
 	c.Any("/", caldav.EntryHandler)
+	c.Any("/principals/*", caldav.PrincipalHandler)
 	c.Any("/principals/*/", caldav.PrincipalHandler)
 	c.Any("/projects", caldav.ProjectHandler)
 	c.Any("/projects/", caldav.ProjectHandler)

pkg/webtests/caldav_test.go

@@ -27,6 +27,7 @@ import (
 	"code.vikunja.io/api/pkg/routes/caldav"
 
 	ics "github.com/arran4/golang-ical"
+	"github.com/labstack/echo/v5"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
@@ -85,6 +86,96 @@ END:VCALENDAR`
 	})
 }
 
+func TestCaldavDiscovery(t *testing.T) {
+	t.Run("Project home set depth 1 includes child projects but not itself", func(t *testing.T) {
+		e, _ := setupTestEnv()
+
+		propfindBody := `<?xml version="1.0" encoding="utf-8" ?>
+<A:propfind xmlns:A="DAV:" xmlns:B="urn:ietf:params:xml:ns:caldav">
+	<A:prop>
+		<A:current-user-principal />
+		<B:calendar-home-set />
+		<A:resourcetype />
+	</A:prop>
+</A:propfind>`
+
+		c, rec := createRequest(e, "PROPFIND", propfindBody, nil, nil)
+		c.Request().Header.Set(echo.HeaderContentType, echo.MIMETextXML)
+		c.Request().Header.Set("Depth", "1")
+		c.Request().URL.Path = caldav.ProjectBasePath + "/"
+		c.Request().RequestURI = caldav.ProjectBasePath + "/"
+
+		result, _ := caldav.BasicAuth(c, testuser15.Username, "12345678")
+		require.True(t, result)
+
+		err := caldav.ProjectHandler(c)
+		require.NoError(t, err)
+		assert.Equal(t, 207, rec.Result().StatusCode)
+
+		responseBody := rec.Body.String()
+		assert.Contains(t, responseBody, "/dav/projects/36")
+		assert.NotContains(t, responseBody, "<d:href>/dav/projects/</d:href>")
+		assert.NotContains(t, responseBody, "<D:href>/dav/projects/</D:href>")
+	})
+
+	t.Run("Project home set depth 0 returns the home set itself", func(t *testing.T) {
+		e, _ := setupTestEnv()
+
+		propfindBody := `<?xml version="1.0" encoding="utf-8" ?>
+<A:propfind xmlns:A="DAV:" xmlns:B="urn:ietf:params:xml:ns:caldav">
+	<A:prop>
+		<A:current-user-principal />
+		<B:calendar-home-set />
+		<A:resourcetype />
+	</A:prop>
+</A:propfind>`
+
+		c, rec := createRequest(e, "PROPFIND", propfindBody, nil, nil)
+		c.Request().Header.Set(echo.HeaderContentType, echo.MIMETextXML)
+		c.Request().Header.Set("Depth", "0")
+		c.Request().URL.Path = caldav.ProjectBasePath + "/"
+		c.Request().RequestURI = caldav.ProjectBasePath + "/"
+
+		result, _ := caldav.BasicAuth(c, testuser15.Username, "12345678")
+		require.True(t, result)
+
+		err := caldav.ProjectHandler(c)
+		require.NoError(t, err)
+		assert.Equal(t, 207, rec.Result().StatusCode)
+
+		responseBody := rec.Body.String()
+		assert.Contains(t, responseBody, "/dav/projects/")
+	})
+
+	t.Run("Principal discovery points to normalized project home set path", func(t *testing.T) {
+		e, _ := setupTestEnv()
+
+		propfindBody := `<?xml version="1.0" encoding="utf-8" ?>
+<A:propfind xmlns:A="DAV:" xmlns:B="urn:ietf:params:xml:ns:caldav">
+	<A:prop>
+		<A:current-user-principal />
+		<B:calendar-home-set />
+	</A:prop>
+</A:propfind>`
+
+		c, rec := createRequest(e, "PROPFIND", propfindBody, nil, nil)
+		c.Request().Header.Set(echo.HeaderContentType, echo.MIMETextXML)
+		c.Request().URL.Path = caldav.PrincipalBasePath + "/user15/"
+		c.Request().RequestURI = caldav.PrincipalBasePath + "/user15/"
+
+		result, _ := caldav.BasicAuth(c, testuser15.Username, "12345678")
+		require.True(t, result)
+
+		err := caldav.PrincipalHandler(c)
+		require.NoError(t, err)
+		assert.Equal(t, 207, rec.Result().StatusCode)
+
+		responseBody := rec.Body.String()
+		assert.Contains(t, responseBody, "<D:href>/dav/projects</D:href>")
+		assert.NotContains(t, responseBody, "/dav//projects/")
+	})
+}
+
 func TestCaldavSubtasks(t *testing.T) {
 	const vtodoHeader = `BEGIN:VCALENDAR
 VERSION:2.0