feat: 🥅 set up proper error handling

Author: arctic-hen7

examples/showcase/app/src/lib.rs

@@ -3,7 +3,7 @@ pub mod pages;
 use sycamore::prelude::*;
 use sycamore_router::{Route, BrowserRouter};
 use wasm_bindgen::prelude::*;
-use perseus::shell::app_shell;
+use perseus::shell::{app_shell, ErrorPages};
 
 // Define our routes
 #[derive(Route)]
@@ -30,6 +30,20 @@ enum AppRoute {
     NotFound
 }
 
+fn get_error_pages() -> ErrorPages {
+    let mut error_pages = ErrorPages::new(Box::new(|_, _, _| template! {
+        p { "Another error occurred." }
+    }));
+    error_pages.add_page(404, Box::new(|_, _, _| template! {
+        p { "Page not found." }
+    }));
+    error_pages.add_page(400, Box::new(|_, _, _| template! {
+        p { "Client error occurred..." }
+    }));
+
+    error_pages
+}
+
 // This is deliberately purely client-side rendered
 #[wasm_bindgen]
 pub fn run() -> Result<(), JsValue> {
@@ -47,34 +61,42 @@ pub fn run() -> Result<(), JsValue> {
         ||
             template! {
                 BrowserRouter(|route: AppRoute| {
+                    // TODO improve performance rather than naively copying error pages for every template
                     match route {
                         AppRoute::Index => app_shell(
                             "index".to_string(),
-                            pages::index::template_fn()
+                            pages::index::template_fn(),
+                            get_error_pages()
                         ),
                         AppRoute::About => app_shell(
                             "about".to_string(),
-                            pages::about::template_fn()
+                            pages::about::template_fn(),
+                            get_error_pages()
                         ),
                         AppRoute::Post { slug } => app_shell(
                             format!("post/{}", slug),
-                            pages::post::template_fn()
+                            pages::post::template_fn(),
+                            get_error_pages()
                         ),
                         AppRoute::NewPost => app_shell(
                             "post/new".to_string(),
-                            pages::new_post::template_fn()
+                            pages::new_post::template_fn(),
+                            get_error_pages()
                         ),
                         AppRoute::Ip => app_shell(
                             "ip".to_string(),
-                            pages::ip::template_fn()
+                            pages::ip::template_fn(),
+                            get_error_pages()
                         ),
                         AppRoute::Time { slug } => app_shell(
                             format!("timeisr/{}", slug),
-                            pages::time::template_fn()
+                            pages::time::template_fn(),
+                            get_error_pages()
                         ),
                         AppRoute::TimeRoot => app_shell(
                             "time".to_string(),
-                            pages::time_root::template_fn()
+                            pages::time_root::template_fn(),
+                            get_error_pages()
                         ),
                         AppRoute::NotFound => template! {
                             p {"Not Found."}

examples/showcase/app/src/pages/ip.rs

@@ -3,6 +3,7 @@
 use serde::{Serialize, Deserialize};
 use sycamore::prelude::{template, component, GenericNode, Template as SycamoreTemplate};
 use perseus::template::Template;
+use perseus::errors::ErrorCause;
 
 #[derive(Serialize, Deserialize)]
 pub struct IpPageProps {
@@ -26,7 +27,8 @@ pub fn get_page<G: GenericNode>() -> Template<G> {
         .template(template_fn())
 }
 
-pub async fn get_request_state(_path: String) -> Result<String, String> {
+pub async fn get_request_state(_path: String) -> Result<String, (String, ErrorCause)> {
+    // Err(("this is a test error!".to_string(), ErrorCause::Client(None)))
     Ok(serde_json::to_string(
         &IpPageProps {
             ip: "x.x.x.x".to_string()

examples/showcase/app/src/pages/post.rs

@@ -44,7 +44,7 @@ pub async fn get_static_props(path: String) -> Result<String, String> {
         }
     ).unwrap())
 }
-// TODO
+
 pub async fn get_static_paths() -> Result<Vec<String>, String> {
     Ok(vec![
         "test".to_string()

examples/showcase/server/src/main.rs

@@ -1,12 +1,14 @@
-use actix_web::{web, App, HttpRequest, HttpServer, Result as ActixResult, error};
+use actix_web::{web, App, HttpRequest, HttpServer, HttpResponse, http::StatusCode};
 use actix_files::{NamedFile};
 use sycamore::prelude::SsrNode;
 use std::collections::HashMap;
 
 use perseus::{
     serve::{get_render_cfg, get_page},
     config_manager::FsConfigManager,
-    template::TemplateMap
+    template::TemplateMap,
+    errors::ErrorKind as PerseusErr,
+    errors::err_to_status_code
 };
 use perseus_showcase_app::pages;
 
@@ -53,12 +55,15 @@ async fn page_data(
     templates: web::Data<TemplateMap<SsrNode>>,
     render_cfg: web::Data<HashMap<String, String>>,
     config_manager: web::Data<FsConfigManager>
-) -> ActixResult<String> {
+) -> HttpResponse {
     let path = req.match_info().query("filename");
-    // TODO match different types of errors here
-    let page_data = get_page(path, &render_cfg, &templates, config_manager.get_ref()).await.map_err(error::ErrorNotFound)?;
+    let page_data = get_page(path, &render_cfg, &templates, config_manager.get_ref()).await;
+    let http_res = match page_data {
+        Ok(page_data) => HttpResponse::Ok().body(
+            serde_json::to_string(&page_data).unwrap()
+        ),
+        Err(err) => HttpResponse::build(StatusCode::from_u16(err_to_status_code(&err)).unwrap()).body(err.to_string()),
+    };
 
-    Ok(
-        serde_json::to_string(&page_data).unwrap()
-    )
+    http_res
 }

src/errors.rs

@@ -3,39 +3,64 @@
 pub use error_chain::bail;
 use error_chain::error_chain;
 
+/// Defines who caused an ambiguous error message so we can reliably create an HTTP status code. Specific status codes may be provided
+/// in either case, or the defaults (400 for client, 500 for server) will be used.
+#[derive(Debug)]
+pub enum ErrorCause {
+    Client(Option<u16>),
+    Server(Option<u16>)
+}
+
+// TODO disclose what information may be revealed over the network through these errors in docs
 // The `error_chain` setup for the whole crate
 error_chain! {
     // The custom errors for this crate (very broad)
     errors {
-        /// For indistinct JavaScript errors.
+        /// For indistinct JavaScript errors (potentially sensitive, but only generated on the client-side).
         JsErr(err: String) {
             description("an error occurred while interfacing with javascript")
             display("the following error occurred while interfacing with javascript: {:?}", err)
         }
+        /// For when a fetched URL didn't return a string, which it must.
+        AssetNotString(url: String) {
+            description("the fetched asset wasn't a string")
+            display("the fetched asset at '{}' wasn't a string", url)
+        }
+        /// For when the server returned a non-200 error code (not including 404, that's handled separately).
+        AssetNotOk(url: String, status: u16, err: String) {
+            description("the asset couldn't be fecthed with a 200 OK")
+            display("the asset at '{}' returned status code '{}' with payload '{}'", url, status, err)
+        }
 
+        /// For when a necessary template feautre was expected but not present. This just pertains to rendering strategies, and shouldn't
+        /// ever be sensitive.
         TemplateFeatureNotEnabled(name: String, feature: String) {
             description("a template feature required by a function called was not present")
             display("the template '{}' is missing the feature '{}'", name, feature)
         }
+        /// For when the given path wasn't found, a 404 should never be sensitive.
         PageNotFound(path: String) {
             description("the requested page was not found")
             display("the requested page at path '{}' was not found", path)
         }
-        NoRenderOpts(template_path: String) {
-            description("a template had no rendering options for use at request-time")
-            display("the template '{}' had no rendering options for use at request-time", template_path)
-        }
+        /// For when the user misconfigured their revalidation length, which should be caught at build time, and hence shouldn't be
+        /// sensitive.
         InvalidDatetimeIntervalIndicator(indicator: String) {
             description("invalid indicator in timestring")
             display("invalid indicator '{}' in timestring, must be one of: s, m, h, d, w, M, y", indicator)
         }
+        /// For when a template defined both build and request states when it can't amalgamate them sensibly, which indicates a misconfiguration.
+        /// Revealing the rendering strategies of a template in this way should never be sensitive. Due to the execution context, this
+        /// doesn't disclose the offending template.
         BothStatesDefined {
             description("both build and request states were defined for a template when only one or fewer were expected")
             display("both build and request states were defined for a template when only one or fewer were expected")
         }
-        RenderFnFailed(fn_name: String, template: String, err_str: String) {
+        /// For when a render function failed. Only request-time functions can generate errors that will be transmitted over the network,
+        /// so **render functions must not disclose sensitive information in errors**. Other information shouldn't be sensitive.
+        RenderFnFailed(fn_name: String, template: String, cause: ErrorCause, err_str: String) {
             description("error while calling render function")
-            display("an error occurred while calling render function '{}' on template '{}': '{}'", fn_name, template, err_str)
+            display("an error caused by '{:?}' occurred while calling render function '{}' on template '{}': '{}'", cause, fn_name, template, err_str)
         }
     }
     links {
@@ -48,3 +73,31 @@ error_chain! {
         ChronoParse(::chrono::ParseError);
     }
 }
+
+pub fn err_to_status_code(err: &Error) -> u16 {
+    match err.kind() {
+        // Misconfiguration
+        ErrorKind::TemplateFeatureNotEnabled(_, _) => 500,
+        // Bad request
+        ErrorKind::PageNotFound(_) => 404,
+        // Misconfiguration
+        ErrorKind::InvalidDatetimeIntervalIndicator(_) => 500,
+        // Misconfiguration
+        ErrorKind::BothStatesDefined => 500,
+        // Ambiguous, we'll rely on the given cause
+        ErrorKind::RenderFnFailed(_, _, cause, _) => match cause {
+            ErrorCause::Client(code) => code.unwrap_or(400),
+            ErrorCause::Server(code) => code.unwrap_or(500),
+        },
+        // We shouldn't be generating JS errors on the server...
+        ErrorKind::JsErr(_) => panic!("function 'err_to_status_code' is only intended for server-side usage"),
+        // These are nearly always server-induced
+        ErrorKind::ConfigManager(_) => 500,
+        ErrorKind::Io(_) => 500,
+        ErrorKind::ChronoParse(_) => 500,
+        // JSON errors can be caused by the client, but we don't have enough information
+        ErrorKind::Json(_) => 500,
+        // Any other errors go to a 500
+        _ => 500
+    }
+}