Treat [data-turbo-stream] as boolean attribute

Replace equality checks for `[data-turbo-stream="true"]` with presence
checks for `[data-turbo-stream]` to more closely match the canonical
behavior for [boolean HTML attributes][].

Turbo already supports other boolean attributes like
`[data-turbo-permanent]` and `[data-turbo-confirm]`, so
`[data-turbo-stream]` should match the precedent.

[boolean HTML attributes]: https://developer.mozilla.org/en-US/docs/Web/HTML/Attributes#boolean_attributes

src/core/drive/form_submission.ts

@@ -1,7 +1,7 @@
 import { FetchRequest, FetchMethod, fetchMethodFromString, FetchRequestHeaders } from "../../http/fetch_request"
 import { FetchResponse } from "../../http/fetch_response"
 import { expandURL } from "../url"
-import { attributeTrue, dispatch } from "../../util"
+import { dispatch } from "../../util"
 import { StreamMessage } from "../streams/stream_message"
 
 export interface FormSubmissionDelegate {
@@ -219,7 +219,7 @@ export class FormSubmission {
   }
 
   requestAcceptsTurboStreamResponse(request: FetchRequest) {
-    return !request.isIdempotent || attributeTrue(this.formElement, "data-turbo-stream")
+    return !request.isIdempotent || this.formElement.hasAttribute("data-turbo-stream")
   }
 }
 

src/core/frames/frame_controller.ts

@@ -7,7 +7,7 @@ import {
 import { FetchMethod, FetchRequest, FetchRequestDelegate, FetchRequestHeaders } from "../../http/fetch_request"
 import { FetchResponse } from "../../http/fetch_response"
 import { AppearanceObserver, AppearanceObserverDelegate } from "../../observers/appearance_observer"
-import { clearBusyState, getAttribute, parseHTMLDocument, markAsBusy, attributeTrue } from "../../util"
+import { clearBusyState, getAttribute, parseHTMLDocument, markAsBusy } from "../../util"
 import { FormSubmission, FormSubmissionDelegate } from "../drive/form_submission"
 import { Snapshot } from "../snapshot"
 import { ViewDelegate } from "../view"
@@ -149,7 +149,7 @@ export class FrameController
   // Link interceptor delegate
 
   shouldInterceptLinkClick(element: Element, _url: string) {
-    if (element.hasAttribute("data-turbo-method") || attributeTrue(element, "data-turbo-stream")) {
+    if (element.hasAttribute("data-turbo-method") || element.hasAttribute("data-turbo-stream")) {
       return false
     } else {
       return this.shouldInterceptNavigation(element)

src/core/session.ts

@@ -12,7 +12,7 @@ import { ScrollObserver } from "../observers/scroll_observer"
 import { StreamMessage } from "./streams/stream_message"
 import { StreamObserver } from "../observers/stream_observer"
 import { Action, Position, StreamSource, isAction } from "./types"
-import { attributeTrue, clearBusyState, dispatch, markAsBusy } from "../util"
+import { clearBusyState, dispatch, markAsBusy } from "../util"
 import { PageView, PageViewDelegate } from "./drive/page_view"
 import { Visit, VisitOptions } from "./drive/visit"
 import { PageSnapshot } from "./drive/page_snapshot"
@@ -174,7 +174,7 @@ export class Session
 
   convertLinkWithMethodClickToFormSubmission(link: Element) {
     const linkMethod = link.getAttribute("data-turbo-method")
-    const useTurboStream = attributeTrue(link, "data-turbo-stream")
+    const useTurboStream = link.hasAttribute("data-turbo-stream")
 
     if (linkMethod || useTurboStream) {
       const form = document.createElement("form")

src/tests/fixtures/form.html

@@ -25,7 +25,7 @@ <h1>Form</h1>
         <input type="hidden" name="greeting" value="Hello from a redirect">
         <input id="standard-get-form-submit" type="submit" value="form[method=get]">
       </form>
-      <form action="/__turbo/redirect" method="get" data-turbo-stream="true" class="redirect">
+      <form action="/__turbo/redirect" method="get" data-turbo-stream class="redirect">
         <input type="hidden" name="path" value="/src/tests/fixtures/form.html">
         <input type="hidden" name="greeting" value="Hello from a redirect">
         <input id="standard-get-form-with-stream-opt-in-submit" type="submit" value="form[method=get]">
@@ -259,8 +259,8 @@ <h2>Frame: Form</h2>
       <a href="/src/tests/fixtures/frames/hello.html" data-turbo-method="get" data-turbo-frame="_top" id="link-method-inside-frame-target-top">Break-out of frame with method link inside frame</a><br />
       <a href="/src/tests/fixtures/frames/hello.html" data-turbo-method="get" data-turbo-frame="hello" id="link-method-inside-frame-with-target">Method link inside frame targeting another frame</a><br />
       <a href="/__turbo/messages?content=Link!&type=stream" data-turbo-method="post" id="stream-link-method-inside-frame">Stream link inside frame</a>
-      <a href="/__turbo/messages?content=Link!&type=stream" data-turbo-method="get" data-turbo-stream="true" id="stream-link-get-method-inside-frame">Stream link GET inside frame</a>
-      <a href="/__turbo/messages?content=Link!&type=stream" data-turbo-stream="true" id="stream-link-inside-frame">Stream link (no method) inside frame</a>
+      <a href="/__turbo/messages?content=Link!&type=stream" data-turbo-method="get" data-turbo-stream id="stream-link-get-method-inside-frame">Stream link GET inside frame</a>
+      <a href="/__turbo/messages?content=Link!&type=stream" data-turbo-stream id="stream-link-inside-frame">Stream link (no method) inside frame</a>
       <a href="/__turbo/messages?content=Link!&type=stream" data-turbo-method="post" data-turbo-confirm="Are you sure?" id="link-method-inside-frame-with-confirmation"data-turbo-confirm="Are you sure?">Stream link inside frame with confirmation</a>
       <form>
         <a href="/src/tests/fixtures/frames/frame.html" data-turbo-method="get" id="method-link-within-form-inside-frame">Method link within form inside frame</a><br />
@@ -290,7 +290,7 @@ <h2>Frame: Form</h2>
     </turbo-frame>
     <a href="/src/tests/fixtures/frames/hello.html" data-turbo-method="get" id="link-method-outside-frame">Method link outside frame</a><br />
     <a href="/__turbo/messages?content=Link!&type=stream" data-turbo-method="post" id="stream-link-method-outside-frame">Stream link outside frame</a>
-    <a href="/__turbo/messages?content=Link!&type=stream" data-turbo-stream="true" id="stream-link-outside-frame">Stream link (no method) outside frame</a>
+    <a href="/__turbo/messages?content=Link!&type=stream" data-turbo-stream id="stream-link-outside-frame">Stream link (no method) outside frame</a>
     <form>
       <a href="/src/tests/fixtures/frames/hello.html" data-turbo-method="get" id="link-method-within-form-outside-frame">Method link within form outside frame</a><br />
       <a href="/__turbo/messages?content=Link!&type=stream" data-turbo-method="post" id="stream-link-method-within-form-outside-frame">Stream link within form outside frame</a>

src/util.ts

@@ -95,7 +95,3 @@ export function clearBusyState(...elements: Element[]) {
     element.removeAttribute("aria-busy")
   }
 }
-
-export function attributeTrue(element: Element, attributeName: string) {
-  return element.getAttribute(attributeName) === "true"
-}