feat: Refactor request to make sure we only use available transports

src/extensions/toolbar.ts

@@ -82,7 +82,7 @@ export class Toolbar {
                         location.hash = state['desiredHash']
                     } else if (history) {
                         // second param is unused see https://developer.mozilla.org/en-US/docs/Web/API/History/replaceState
-                        history.replaceState(history.state, "", location.pathname + location.search) // completely remove hash
+                        history.replaceState(history.state, '', location.pathname + location.search) // completely remove hash
                     } else {
                         location.hash = '' // clear hash (but leaves # unfortunately)
                     }

src/posthog-core.ts

@@ -116,7 +116,6 @@ let ENQUEUE_REQUESTS = !SUPPORTS_REQUEST && userAgent?.indexOf('MSIE') === -1 &&
 
 export const defaultConfig = (): PostHogConfig => ({
     api_host: 'https://us.i.posthog.com',
-    api_transport: 'XHR',
     ui_host: null,
     token: '',
     autocapture: true,

src/request.ts

@@ -1,4 +1,4 @@
-import { _base64Encode, each } from './utils'
+import { _base64Encode, each, find } from './utils'
 import Config from './config'
 import { Compression, RequestOptions, RequestResponse } from './types'
 import { formDataToQuery } from './utils/request-utils'
@@ -19,36 +19,6 @@ type EncodedBody = {
     body: string | BlobPart
 }
 
-// This is the entrypoint. It takes care of sanitizing the options and then calls the appropriate request method.
-export const request = (_options: RequestOptions) => {
-    // Clone the options so we don't modify the original object
-    const options = { ..._options }
-    options.timeout = options.timeout || 60000
-
-    options.url = extendURLParams(options.url, {
-        _: new Date().getTime().toString(),
-        ver: Config.LIB_VERSION,
-        compression: options.compression,
-    })
-
-    if (options.transport === 'sendBeacon' && navigator?.sendBeacon) {
-        return _sendBeacon(options)
-    }
-
-    // NOTE: Until we are confident with it, we only use fetch if explicitly told so
-    // At some point we will make it the default over xhr
-    if (options.transport === 'fetch' && fetch) {
-        return _fetch(options)
-    }
-
-    if (XMLHttpRequest || !document) {
-        return xhr(options)
-    }
-
-    // Final fallback if everything else fails...
-    scriptRequest(options)
-}
-
 export const extendURLParams = (url: string, params: Record<string, any>): string => {
     const [baseUrl, search] = url.split('?')
     const newParams = { ...params }
@@ -225,3 +195,57 @@ const scriptRequest = (options: RequestOptions) => {
     const s = document.getElementsByTagName('script')[0]
     s.parentNode?.insertBefore(script, s)
 }
+
+const AVAILABLE_TRANSPORTS: { transport: RequestOptions['transport']; method: (options: RequestOptions) => void }[] = []
+
+// We add the transports in order of preference
+
+if (XMLHttpRequest) {
+    AVAILABLE_TRANSPORTS.push({
+        transport: 'XHR',
+        method: xhr,
+    })
+}
+
+if (fetch) {
+    AVAILABLE_TRANSPORTS.push({
+        transport: 'fetch',
+        method: _fetch,
+    })
+}
+
+if (navigator?.sendBeacon) {
+    AVAILABLE_TRANSPORTS.push({
+        transport: 'sendBeacon',
+        method: _sendBeacon,
+    })
+}
+
+AVAILABLE_TRANSPORTS.push({
+    transport: undefined,
+    method: scriptRequest,
+})
+
+// This is the entrypoint. It takes care of sanitizing the options and then calls the appropriate request method.
+export const request = (_options: RequestOptions) => {
+    // Clone the options so we don't modify the original object
+    const options = { ..._options }
+    options.timeout = options.timeout || 60000
+
+    options.url = extendURLParams(options.url, {
+        _: new Date().getTime().toString(),
+        ver: Config.LIB_VERSION,
+        compression: options.compression,
+    })
+
+    const transport = options.transport ?? 'XHR'
+
+    const transportMethod =
+        find(AVAILABLE_TRANSPORTS, (t) => t.transport === transport)?.method ?? AVAILABLE_TRANSPORTS[0].method
+
+    if (!transportMethod) {
+        throw new Error('No available transport method')
+    }
+
+    transportMethod(options)
+}

src/utils/index.ts

@@ -444,3 +444,12 @@ export function isCrossDomainCookie(documentLocation: Location | undefined) {
 export function isDistinctIdStringLike(value: string): boolean {
     return ['distinct_id', 'distinctid'].includes(value.toLowerCase())
 }
+
+export function find<T>(value: T[], predicate: (value: T) => boolean): T | undefined {
+    for (let i = 0; i < value.length; i++) {
+        if (predicate(value[i])) {
+            return value[i]
+        }
+    }
+    return undefined
+}