move header injection to FormSubmission

src/core/drive/form_submission.ts

@@ -78,7 +78,7 @@ export class FormSubmission {
   // Fetch request delegate
 
   additionalHeadersForRequest(request: FetchRequest) {
-    const headers: FetchRequestHeaders = {}
+    const headers: FetchRequestHeaders = { Accept: "text/html; turbo-stream" }
     if (this.method != FetchMethod.get) {
       const token = getCookieValue(getMetaContent("csrf-param")) || getMetaContent("csrf-token")
       if (token) {

src/observers/stream_observer.ts

@@ -1,4 +1,3 @@
-import { FormSubmission } from "../core/drive/form_submission"
 import { FetchResponse } from "../http/fetch_response"
 import { StreamMessage } from "../core/streams/stream_message"
 import { StreamSource } from "../core/types"
@@ -19,15 +18,13 @@ export class StreamObserver {
   start() {
     if (!this.started) {
       this.started = true
-      addEventListener("turbo:submit-start", this.prepareFormSubmission, true)
       addEventListener("turbo:before-fetch-response", this.inspectFetchResponse, false)
     }
   }
 
   stop() {
     if (this.started) {
       this.started = false
-      removeEventListener("turbo:submit-start", this.prepareFormSubmission, true)
       removeEventListener("turbo:before-fetch-response", this.inspectFetchResponse, false)
     }
   }
@@ -50,15 +47,6 @@ export class StreamObserver {
     return this.sources.has(source)
   }
 
-  prepareFormSubmission = <EventListener>((event: CustomEvent) => {
-    const formSubmission: FormSubmission = event.detail?.formSubmission
-    const headers: any = formSubmission.fetchRequest.fetchOptions.headers
-
-    if (headers) {
-      headers.Accept = [ "text/html; turbo-stream", headers.Accept ].join(", ")
-    }
-  })
-
   inspectFetchResponse = <EventListener>((event: CustomEvent) => {
     const response = fetchResponseFromEvent(event)
     if (response && fetchResponseIsStream(response)) {