reuse existing usercss installer tab

A few additional checks were needed to circumvent FF bugs
so openURL was refactored to keep the code readable

background/usercss-helper.js

@@ -116,6 +116,7 @@ var usercssHelper = (() => {
         (direct ? '&direct=yes' : ''),
       index: tab.index + 1,
       openerTabId: tab.id,
+      currentWindow: null,
     }));
   }
 

install-usercss/install-usercss.js

@@ -9,6 +9,7 @@
   let installed = false;
 
   const tabId = Number(params.get('tabId'));
+  let tabUrl;
   let port;
 
   if (params.has('direct')) {
@@ -35,7 +36,7 @@
           break;
       }
     });
-    port.onDisconnect.addListener(closeCurrentTab);
+    port.onDisconnect.addListener(onPortDisconnected);
   }
 
   const cm = CodeMirror($('.main'), {readOnly: true});
@@ -49,6 +50,12 @@
     }
   }, 200);
 
+  getTab(tabId).then(tab => (tabUrl = tab.url));
+  chrome.tabs.onUpdated.addListener((id, {url}) =>
+    id === tabId &&
+    url && url !== tabUrl &&
+    closeCurrentTab());
+
   function liveReloadUpdate(sourceCode) {
     liveReloadPending = liveReloadPending.then(() => {
       const scrollInfo = cm.getScrollInfo();
@@ -391,4 +398,14 @@
         .catch(err => messageBox.alert(t('styleInstallFailed', String(err))));
     });
   }
+
+  function onPortDisconnected() {
+    chrome.tabs.get(tabId, tab => {
+      if (chrome.runtime.lastError) {
+        closeCurrentTab();
+      } else if (tab.url === tabUrl) {
+        location.reload();
+      }
+    });
+  }
 })();

js/messaging.js

@@ -210,43 +210,63 @@ function getTabRealURL(tab) {
   });
 }
 
-
+/**
-// opens a tab or activates the already opened one,
+ * Opens a tab or activates an existing one,
-// reuses the New Tab page if it's focused now
+ * reuses the New Tab page or about:blank if it's focused now
-function openURL({url, index, active, currentWindow = true}) {
+ * @param {Object} params - or just a string e.g. openURL('foo')
-  if (!url.includes('://')) {
+ * @param {string} params.url - if relative, it's auto-expanded to the full extension URL
-    url = chrome.runtime.getURL(url);
+ * @param {number} [params.index] - move the tab to this index in the tab strip, -1 = last
-  }
+ * @param {Boolean} [params.active=tue] - true to activate the tab, false to open in background
-  return new Promise(resolve => {
+ * @param {?Boolean} [params.currentWindow=true] - pass null to check all windows
+ * @returns {Promise}
+ */
+function openURL({
+  url = arguments[0],
+  index,
+  active,
+  currentWindow = true,
+}) {
+  url = url.includes('://') ? url : chrome.runtime.getURL(url);
   // [some] chromium forks don't handle their fake branded protocols
   url = url.replace(/^(opera|vivaldi)/, 'chrome');
   // FF doesn't handle moz-extension:// URLs (bug)
+  // FF decodes %2F in encoded parameters (bug)
   // API doesn't handle the hash-fragment part
-    const urlQuery = url.startsWith('moz-extension') ? undefined : url.replace(/#.*/, '');
+  const urlQuery = url.startsWith('moz-extension') ? undefined :
-    queryTabs({url: urlQuery, currentWindow}).then(tabs => {
+    FIREFOX && url.includes('%2F') ?
-      for (const tab of tabs) {
+      url.replace(/%2F.*/, '*').replace(/#.*/, '') :
-        if (tab.url === url) {
+      url.replace(/#.*/, '');
-          activateTab(tab).then(resolve);
+  return queryTabs({url: urlQuery, currentWindow}).then(maybeSwitch);
-          return;
+
+  function maybeSwitch(tabs = []) {
+    const urlFF = FIREFOX && url.replace(/%2F/g, '/');
+    const tab = tabs.find(tab => tab.url === url || tab.url === urlFF);
+    if (!tab) {
+      return getActiveTab().then(maybeReplace);
     }
+    if (index !== undefined && tab.index !== index) {
+      chrome.tabs.move(tab.id, {index});
     }
-      getActiveTab().then(tab => {
+    return activateTab(tab);
+  }
+
+  // update current NTP or about:blank
+  // except when 'url' is chrome:// or chrome-extension:// in incognito
+  function maybeReplace(tab) {
     const chromeInIncognito = tab && tab.incognito && url.startsWith('chrome');
-        if (tab && (tab.url === 'chrome://newtab/' || tab.url === 'about:newtab') && !chromeInIncognito) {
+    const emptyTab = tab && (tab.url === 'chrome://newtab/' || tab.url === 'about:newtab');
-          // update current NTP, except for chrome:// or chrome-extension:// in incognito
+    if (emptyTab && !chromeInIncognito) {
-          chrome.tabs.update({url}, resolve);
+      return new Promise(resolve =>
-        } else {
+        chrome.tabs.update({url}, resolve));
-          // create a new tab
+    }
     const options = {url, index, active};
     // FF57+ supports openerTabId, but not in Android (indicated by the absence of chrome.windows)
     if (tab && (!FIREFOX || FIREFOX >= 57 && chrome.windows) && !chromeInIncognito) {
       options.openerTabId = tab.id;
     }
-          chrome.tabs.create(options, resolve);
+    return new Promise(resolve =>
+      chrome.tabs.create(options, resolve));
   }
-      });
-    });
-  });
 }