feat: Enable the browser agent to run in extension background contexts (#1206)

Thanks for contributing @jspivack !

Author: jspivack

src/common/harvest/harvest.js

@@ -144,6 +144,25 @@ export class Harvest extends SharedContext {
         }
         cbFinished(cbResult)
       }, eventListenerOpts(false))
+    } else if (!opts.unload && cbFinished && submitMethod === submitData.xhrFetch) {
+      const harvestScope = this
+      result.then(async function (response) {
+        const status = response.status
+        const cbResult = { sent: true, status, fullUrl, fetchResponse: response }
+
+        if (response.status === 429) {
+          cbResult.retry = true
+          cbResult.delay = harvestScope.tooManyRequestsDelay
+        } else if (status === 408 || status === 500 || status === 503) {
+          cbResult.retry = true
+        }
+
+        if (opts.needResponse) {
+          cbResult.responseText = await response.text()
+        }
+
+        cbFinished(cbResult)
+      })
     }
 
     return result

src/common/util/submit-data.js

@@ -17,11 +17,44 @@ import { isBrowserScope } from '../constants/runtime'
  * a final harvest within the agent.
  */
 export function getSubmitMethod ({ isFinalHarvest = false } = {}) {
-  return isFinalHarvest && isBrowserScope
+  if (isFinalHarvest && isBrowserScope) {
     // Use sendBeacon for final harvest
-    ? beacon
-    // If not final harvest, or not browserScope, always use xhr post
-    : xhr
+    return beacon
+  }
+
+  // If not final harvest, or not browserScope, use XHR post if available
+  if (typeof XMLHttpRequest !== 'undefined') {
+    return xhr
+  }
+
+  // Fallback for web workers where XMLHttpRequest is not available
+  return xhrFetch
+}
+
+/**
+ *
+ * @param url
+ * @param body
+ * @param method
+ * @param headers
+ * @returns {Promise<Response>}
+ */
+export function xhrFetch ({
+  url,
+  body = null,
+  method = 'POST',
+  headers = [{
+    key: 'content-type',
+    value: 'text/plain'
+  }]
+}) {
+  const objHeaders = {}
+
+  for (const header of headers) {
+    objHeaders[header.key] = header.value
+  }
+
+  return fetch(url, { headers: objHeaders, method, body, credentials: 'include' })
 }
 
 /**

src/common/wrap/wrap-events.js

@@ -37,8 +37,8 @@ export function wrapEvents (sharedEE) {
   // Guard against instrumenting environments w/o necessary features
   if ('getPrototypeOf' in Object) {
     if (isBrowserScope) findEventListenerProtoAndCb(document, wrapNode)
+    if (XHR) findEventListenerProtoAndCb(XHR.prototype, wrapNode)
     findEventListenerProtoAndCb(globalScope, wrapNode)
-    findEventListenerProtoAndCb(XHR.prototype, wrapNode)
   }
 
   ee.on(ADD_EVENT_LISTENER + '-start', function (args, target) {

src/common/wrap/wrap-xhr.js

@@ -28,6 +28,8 @@ export function wrapXhr (sharedEE) {
   var baseEE = sharedEE || contextualEE
   const ee = scopedEE(baseEE)
 
+  if (typeof globalScope.XMLHttpRequest === 'undefined') return ee
+
   // Notice if our wrapping never ran yet, the falsy NaN will not early return; but if it has,
   // then we increment the count to track # of feats using this at runtime.
   if (wrapped[ee.debugId]++) return ee