handling 5xx HTTP errors directly in the service worker (ref. #36)

plugins/fetch/index.js

@@ -32,13 +32,11 @@
             // run built-in regular fetch()
             return fetch(url, init)
                 .then((response) => {
-                    // 5xx? that's a paddlin'
-                    // we do want to pass 3xx and 4xx on back to the client though!
-                    if (response.status >= 500) {
-                        // throw an Error to fall back to LibResilient:
-                        throw new Error('HTTP Error: ' + response.status + ' ' + response.statusText);
-                    }
-                    // all good, it seems
+
+                    // we got something, it seems
+                    // it might be a 2xx; it might be a 3xx redirect
+                    // it might also be a 4xx or a 5xx error
+                    // the service worker will know how to deal with those
                     LR.log(pluginName, `fetched:\n+-- url: ${response.url}\n+-- http status: ${response.status} (${response.statusText})`);
                     
                     // we need to create a new Response object

service-worker.js

@@ -1045,7 +1045,18 @@ let libresilientFetch = (plugin, url, init, reqInfo) => {
         // starting the fetch...
         // if it errors out immediately, at least we don't have to deal
         // with a dangling promise timeout, set up below
-        let fetch_promise = plugin.fetch(url, init)
+        let fetch_promise = plugin
+                                .fetch(url, init)
+                                .then((response)=>{
+                                    // 5xx? that's a paddlin'
+                                    // we do want to pass 3xx and 4xx on back to the client though!
+                                    if (response.status >= 500) {
+                                        // throw an Error to fall back to LibResilient:
+                                        throw new Error('HTTP Error: ' + response.status + ' ' + response.statusText);
+                                    }
+                                    // ok, we're good
+                                    return response
+                                })
         
         let timeout_promise, timeout_id
         [timeout_promise, timeout_id] = promiseTimeout(
@@ -1256,7 +1267,7 @@ let getResourceThroughLibResilient = (url, init, clientId, useStashed=true, doSt
         })
         // a final catch... in case all plugins fail
         .catch((err)=>{
-            self.log('service-worker', "LibResilient failed completely: ", err,
+            self.log('service-worker', "all plugins failed: ", err,
                         '\n+-- URL    : ' + url)
 
             // cleanup
@@ -1264,7 +1275,17 @@ let getResourceThroughLibResilient = (url, init, clientId, useStashed=true, doSt
                 state: "failed",
                 error: err
             })
+            
             decrementActiveFetches(clientId)
+            
+            // print out all the errors from plugins in console for debugging purposes
+            self.log('service-worker', `request errored out:\n+-- url: ${reqInfo.url}\n+-- plugin errors:\n${
+                reqInfo
+                    .errors
+                    .reduce((acc, cur)=>{
+                        return acc + '    ' + cur.join(': ') + '\n'
+                    }, '')}`)
+            
             // rethrow
             throw err
         })