refactor(fetch): Pass Request construction errors to the caller

Author: TatriX

src/browser/fetch.rs

@@ -30,6 +30,7 @@
 
 use crate::util::window;
 use serde_json;
+use std::convert::TryInto;
 use wasm_bindgen_futures::JsFuture;
 use web_sys;
 
@@ -72,7 +73,8 @@ pub type Result<T> = std::result::Result<T, FetchError>;
 /// even if you get `Ok` from this function, you still need to check
 /// `Response` status for HTTP errors.
 pub async fn fetch<'a>(request: impl Into<Request<'a>>) -> Result<Response> {
-    let promise = window().fetch_with_request(&request.into().into());
+    let request = request.into();
+    let promise = window().fetch_with_request(&request.try_into()?);
 
     let raw_response = JsFuture::from(promise)
         .await
@@ -89,6 +91,8 @@ pub enum FetchError {
     DomException(web_sys::DomException),
     PromiseError(wasm_bindgen::JsValue),
     NetworkError(wasm_bindgen::JsValue),
+    /// Request construction failed.
+    RequestError(wasm_bindgen::JsValue),
     StatusError(Status),
 }
 

src/browser/fetch/request.rs

@@ -4,7 +4,7 @@ use super::{FetchError, Header, Headers, Method, Result};
 use crate::browser::Url;
 use gloo_timers::callback::Timeout;
 use serde::Serialize;
-use std::{borrow::Cow, cell::RefCell, rc::Rc};
+use std::{borrow::Cow, cell::RefCell, convert::TryFrom, rc::Rc};
 use wasm_bindgen::JsValue;
 
 /// Its methods configure the request, and handle the response. Many of them return the original
@@ -174,16 +174,17 @@ impl<'a> From<Url> for Request<'a> {
     }
 }
 
-impl From<Request<'_>> for web_sys::Request {
-    fn from(request: Request) -> Self {
+impl TryFrom<Request<'_>> for web_sys::Request {
+    type Error = FetchError;
+    fn try_from(request: Request) -> std::result::Result<Self, Self::Error> {
         let mut init = web_sys::RequestInit::new();
 
         // headers
-        let headers = web_sys::Headers::new().expect("fetch: cannot create headers");
+        let headers = web_sys::Headers::new().map_err(FetchError::RequestError)?;
         for header in request.headers {
             headers
                 .append(&header.name, &header.value)
-                .expect("fetch: cannot create header")
+                .map_err(FetchError::RequestError)?;
         }
         init.headers(&headers);
 
@@ -250,7 +251,7 @@ impl From<Request<'_>> for web_sys::Request {
         //
         // See https://developer.mozilla.org/en-US/docs/Web/API/Request/Request#Errors
         web_sys::Request::new_with_str_and_init(&request.url, &init)
-            .expect("fetch: Cannot create request")
+            .map_err(FetchError::RequestError)
     }
 }