Make the template contexts a bit more clear

crates/core/src/handlers/views/reauth.rs

@@ -27,7 +27,7 @@ use crate::{
         with_templates, CsrfToken,
     },
     storage::SessionInfo,
-    templates::{TemplateContext, Templates},
+    templates::{EmptyContext, TemplateContext, Templates},
 };
 
 #[derive(Deserialize, Debug)]
@@ -63,7 +63,7 @@ async fn get(
     csrf_token: CsrfToken,
     session: SessionInfo,
 ) -> Result<impl Reply, Rejection> {
-    let ctx = ().with_session(session).with_csrf(&csrf_token);
+    let ctx = EmptyContext.with_session(session).with_csrf(&csrf_token);
 
     let content = templates.render_reauth(&ctx)?;
     let reply = html(content);

crates/core/src/handlers/views/register.rs

@@ -31,7 +31,7 @@ use crate::{
         with_templates, CsrfToken,
     },
     storage::{register_user, user::start_session, SessionInfo},
-    templates::{TemplateContext, Templates},
+    templates::{EmptyContext, TemplateContext, Templates},
 };
 
 #[derive(Serialize, Deserialize)]
@@ -115,7 +115,7 @@ async fn get(
     if maybe_session.is_some() {
         Ok(Box::new(query.redirect()?))
     } else {
-        let ctx = ().with_csrf(&csrf_token);
+        let ctx = EmptyContext.with_csrf(&csrf_token);
         let content = templates.render_register(&ctx)?;
         let reply = html(content);
         let reply = cookie_saver.save_encrypted(&csrf_token, reply)?;

crates/core/src/templates/context.rs

@@ -19,22 +19,31 @@ use url::Url;
 use crate::{errors::ErroredForm, filters::CsrfToken, storage::SessionInfo};
 
 /// Helper trait to construct context wrappers
-pub trait TemplateContext: Sized {
-    fn with_session(self, current_session: SessionInfo) -> WithSession<Self> {
+pub trait TemplateContext {
+    fn with_session(self, current_session: SessionInfo) -> WithSession<Self>
+    where
+        Self: Sized,
+    {
         WithSession {
             current_session,
             inner: self,
         }
     }
 
-    fn maybe_with_session(self, current_session: Option<SessionInfo>) -> WithOptionalSession<Self> {
+    fn maybe_with_session(self, current_session: Option<SessionInfo>) -> WithOptionalSession<Self>
+    where
+        Self: Sized,
+    {
         WithOptionalSession {
             current_session,
             inner: self,
         }
     }
 
-    fn with_csrf(self, token: &CsrfToken) -> WithCsrf<Self> {
+    fn with_csrf(self, token: &CsrfToken) -> WithCsrf<Self>
+    where
+        Self: Sized,
+    {
         WithCsrf {
             csrf_token: token.form_value(),
             inner: self,
@@ -42,13 +51,13 @@ pub trait TemplateContext: Sized {
     }
 }
 
-impl TemplateContext for () {}
+impl TemplateContext for EmptyContext {}
 impl TemplateContext for IndexContext {}
 impl TemplateContext for LoginContext {}
-impl<T: Sized> TemplateContext for FormPostContext<T> {}
-impl<T: Sized> TemplateContext for WithSession<T> {}
-impl<T: Sized> TemplateContext for WithOptionalSession<T> {}
-impl<T: Sized> TemplateContext for WithCsrf<T> {}
+impl<T> TemplateContext for FormPostContext<T> {}
+impl<T> TemplateContext for WithSession<T> {}
+impl<T> TemplateContext for WithOptionalSession<T> {}
+impl<T> TemplateContext for WithCsrf<T> {}
 
 /// Context with a CSRF token in it
 #[derive(Serialize)]
@@ -77,6 +86,10 @@ pub struct WithOptionalSession<T> {
     inner: T,
 }
 
+/// An empty context used for composition
+#[derive(Serialize)]
+pub struct EmptyContext;
+
 // Context used by the `index.html` template
 #[derive(Serialize)]
 pub struct IndexContext {

crates/core/src/templates/mod.rs

@@ -27,8 +27,8 @@ mod context;
 mod macros;
 
 pub use self::context::{
-    ErrorContext, FormPostContext, IndexContext, LoginContext, LoginFormField, TemplateContext,
-    WithCsrf, WithOptionalSession, WithSession,
+    EmptyContext, ErrorContext, FormPostContext, IndexContext, LoginContext, LoginFormField,
+    TemplateContext, WithCsrf, WithOptionalSession, WithSession,
 };
 
 #[derive(Clone)]
@@ -163,13 +163,13 @@ register_templates! {
     pub fn render_login(WithCsrf<LoginContext>) { "login.html" }
 
     /// Render the registration page
-    pub fn render_register(WithCsrf<()>) { "register.html" }
+    pub fn render_register(WithCsrf<EmptyContext>) { "register.html" }
 
     /// Render the home page
     pub fn render_index(WithCsrf<WithOptionalSession<IndexContext>>) { "index.html" }
 
     /// Render the re-authentication form
-    pub fn render_reauth(WithCsrf<WithSession<()>>) { "reauth.html" }
+    pub fn render_reauth(WithCsrf<WithSession<EmptyContext>>) { "reauth.html" }
 
     /// Render the form used by the form_post response mode
     pub fn render_form_post<T: Serialize>(FormPostContext<T>) { "form_post.html" }