Check for valid script as content is received

src/bg/user-script-detect.js

@@ -16,6 +16,20 @@ const userScriptTypes = {
 };
 
 
+// Check if enough content is available to open an install message
+function checkScript(userScriptContent, url, tabId) {
+  let scriptDetails = parseUserScript(userScriptContent, url, true);
+  if (scriptDetails) {
+    let installUrl = browser.runtime.getURL('src/content/install-dialog.html')
+        + '?' + escape(JSON.stringify(scriptDetails));
+    browser.tabs.update(tabId, {'url': installUrl, 'loadReplace': true});
+    return true;
+  } else {
+    return false;
+  }
+}
+
+
 function detectUserScriptOnHeadersReceived(details) {
   let hasContentType = false;
   for (header of details.responseHeaders) {
@@ -38,35 +52,26 @@ function detectUserScriptOnHeadersReceived(details) {
   let userScriptUrl = details.url;
   let userScriptContent = '';
 
-  // Not sure if this is called more than once. If it's only called once
-  // then just use event.data directly rather than concatenating and then
-  // doing the checks in onstop.
   filter.ondata = event => {
     userScriptContent = userScriptContent
                       + decoder.decode(event.data, {'stream': true});
+    if (checkScript(userScriptContent, details.url, details.tabId)) {
+      // We have enough for the details. Since a entire tab is currently used
+      // for the install dialog, close the filter so the request stops
+      // processing.
+      filter.close();
+    }
   };
   filter.onstop = event => {
-    let userScriptDetails;
-    try {
-      userScriptDetails = parseUserScript(userScriptContent, userScriptUrl, true);
-    } catch (err) {
-      console.log('Error parsing user script:', userScriptUrl, err);
+    // One last check to see if we have a valid script.
+    if (checkScript(userScriptContent, details.url, details.tabId)) {
+      // Close the filter without further processing.
+      filter.close();
+    } else {
+      // No script, flush our content to the filter and close.
       filter.write(encoder.encode(userScriptContent));
-      filter.disconnect();
-      return;
+      filter.close();
     }
-
-    if (userScriptDetails === null) {
-      console.log('User script details were null:', userScriptUrl);
-      filter.write(encoder.encode(userScriptContent));
-      filter.disconnect();
-      return;
-    }
-
-    let installUrl = browser.runtime.getURL('src/content/install-dialog.html')
-        + '?' + escape(JSON.stringify(userScriptDetails));
-    browser.tabs.update(details.tabId, {'url': installUrl, 'loadReplace': true});
-    filter.close();
   };
 
   return {};