minor improvements, including fetch plugin now returning 4xx errors directly as Response objects (ref. #36)

plugins/delay/index.js

@@ -35,6 +35,11 @@
         // merge the defaults with settings from init
         let config = {...defaultConfig, ...init}
         
+        // reality check: if no wrapped plugin configured, or more than one, complain
+        if (config.uses.length != 1) {
+            throw new Error(`Expected exactly one plugin to wrap, but ${config.uses.length} configured.`)
+        }
+        
         /**
         * getting content using regular HTTP(S) fetch()
         */

plugins/fetch/index.js

@@ -32,13 +32,14 @@
             // run built-in regular fetch()
             return fetch(url, init)
                 .then((response) => {
-                    // 4xx? 5xx? that's a paddlin'
-                    if (response.status >= 400) {
+                    // 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
-                    LR.log(pluginName, `fetched successfully: ${response.url}`);
+                    LR.log(pluginName, `fetched:\n+-- url: ${response.url}\n+-- http status: ${response.status} (${response.statusText})`);
                     
                     // we need to create a new Response object
                     // with all the headers added explicitly,

service-worker.js

@@ -820,6 +820,8 @@ let LibResilientClient = class {
     
     constructor(clientId) {
         
+        self.log('service-worker', `new client: ${clientId}`)
+        
         // we often get the clientId long before
         // we are able to get a valid client out of it
         //