Introduce Turbo.config object

The initial implementation aims to replace the ad hoc configurations
spread across `window.Turbo` and `Turbo.session`. Those objects
shouldn't be considered part of the public interface, especially for
extension.

This commit exports a single object from `src/core/config` to serve as a
centralized, user-facing repository for configuration values.

The main `src/core/config` object is composed of two constituent parts:

* `src/core/config/drive`
* `src/core/config/forms`

In the future, the directory structure can be expanded upon to suit the
needs of the project.

Any user-facing configuration outside of `Turbo.config` is deprecated.

src/core/config/drive.js

@@ -0,0 +1,4 @@
+export const drive = {
+  enabled: true,
+  progressBarDelay: 500
+}

src/core/config/forms.js

@@ -0,0 +1,3 @@
+export const forms = {
+  mode: "on"
+}

src/core/config/index.js

@@ -0,0 +1,7 @@
+import { drive } from "./drive"
+import { forms } from "./forms"
+
+export const config = {
+  drive,
+  forms
+}

src/core/drive/form_submission.js

@@ -3,6 +3,7 @@ import { expandURL } from "../url"
 import { clearBusyState, dispatch, getAttribute, getMetaContent, hasAttribute, markAsBusy } from "../../util"
 import { StreamMessage } from "../streams/stream_message"
 import { prefetchCache } from "./prefetch_cache"
+import { config } from "../config"
 
 export const FormSubmissionState = {
   initialized: "initialized",
@@ -22,7 +23,7 @@ export const FormEnctype = {
 export class FormSubmission {
   state = FormSubmissionState.initialized
 
-  static confirmMethod(message, _element, _submitter) {
+  static confirmMethod(message) {
     return Promise.resolve(confirm(message))
   }
 
@@ -78,7 +79,11 @@ export class FormSubmission {
     const confirmationMessage = getAttribute("data-turbo-confirm", this.submitter, this.formElement)
 
     if (typeof confirmationMessage === "string") {
-      const answer = await FormSubmission.confirmMethod(confirmationMessage, this.formElement, this.submitter)
+      const confirmMethod = typeof config.forms.confirm === "function" ?
+        config.forms.confirm :
+        FormSubmission.confirmMethod
+
+      const answer = await confirmMethod(confirmationMessage, this.formElement, this.submitter)
       if (!answer) {
         return
       }

src/core/index.js

@@ -2,12 +2,12 @@ import { Session } from "./session"
 import { PageRenderer } from "./drive/page_renderer"
 import { PageSnapshot } from "./drive/page_snapshot"
 import { FrameRenderer } from "./frames/frame_renderer"
-import { FormSubmission } from "./drive/form_submission"
 import { fetch, recentRequests } from "../http/fetch"
+import { config } from "./config"
 
 const session = new Session(recentRequests)
 const { cache, navigator } = session
-export { navigator, session, cache, PageRenderer, PageSnapshot, FrameRenderer, fetch }
+export { navigator, session, cache, PageRenderer, PageSnapshot, FrameRenderer, fetch, config }
 
 /**
  * Starts the main session.
@@ -97,13 +97,22 @@ export function clearCache() {
  * @param delay Time to delay in milliseconds
  */
 export function setProgressBarDelay(delay) {
-  session.setProgressBarDelay(delay)
+  console.warn(
+    "Please replace `Turbo.setProgressBarDelay(delay)` with `Turbo.config.drive.progressBarDelay = delay`. The top-level function is deprecated and will be removed in a future version of Turbo.`"
+  )
+  config.drive.progressBarDelay = delay
 }
 
 export function setConfirmMethod(confirmMethod) {
-  FormSubmission.confirmMethod = confirmMethod
+  console.warn(
+    "Please replace `Turbo.setConfirmMethod(confirmMethod)` with `Turbo.config.forms.confirm = confirmMethod`. The top-level function is deprecated and will be removed in a future version of Turbo.`"
+  )
+  config.forms.confirm = confirmMethod
 }
 
 export function setFormMode(mode) {
-  session.setFormMode(mode)
+  console.warn(
+    "Please replace `Turbo.setFormMode(mode)` with `Turbo.config.forms.mode = mode`. The top-level function is deprecated and will be removed in a future version of Turbo.`"
+  )
+  config.forms.mode = mode
 }

src/core/session.js

@@ -18,6 +18,7 @@ import { PageView } from "./drive/page_view"
 import { FrameElement } from "../elements/frame_element"
 import { Preloader } from "./drive/preloader"
 import { Cache } from "./cache"
+import { config } from "./config"
 
 export class Session {
   navigator = new Navigator(this)
@@ -37,11 +38,8 @@ export class Session {
   streamMessageRenderer = new StreamMessageRenderer()
   cache = new Cache(this)
 
-  drive = true
   enabled = true
-  progressBarDelay = 500
   started = false
-  formMode = "on"
   #pageRefreshDebouncePeriod = 150
 
   constructor(recentRequests) {
@@ -135,7 +133,10 @@ export class Session {
   }
 
   setFormMode(mode) {
-    this.formMode = mode
+    console.warn(
+      "Please replace `Turbo.session.formMode = mode` with `Turbo.config.forms.mode = mode`. The `Turbo.session.formMode` property is deprecated and will be removed in a future version of Turbo.`"
+    )
+    config.forms.mode = mode
   }
 
   get location() {
@@ -425,12 +426,12 @@ export class Session {
   // Helpers
 
   submissionIsNavigatable(form, submitter) {
-    if (this.formMode == "off") {
+    if (config.forms.mode == "off") {
       return false
     } else {
       const submitterIsNavigatable = submitter ? this.elementIsNavigatable(submitter) : true
 
-      if (this.formMode == "optin") {
+      if (config.forms.mode == "optin") {
         return submitterIsNavigatable && form.closest('[data-turbo="true"]') != null
       } else {
         return submitterIsNavigatable && this.elementIsNavigatable(form)
@@ -443,7 +444,7 @@ export class Session {
     const withinFrame = findClosestRecursively(element, "turbo-frame")
 
     // Check if Drive is enabled on the session or we're within a Frame.
-    if (this.drive || withinFrame) {
+    if (config.drive.enabled || withinFrame) {
       // Element is navigatable by default, unless `data-turbo="false"`.
       if (container) {
         return container.getAttribute("data-turbo") != "false"
@@ -460,6 +461,33 @@ export class Session {
     }
   }
 
+  get drive() {
+    return config.drive.enabled
+  }
+
+  set drive(value) {
+    console.warn(
+      "Please replace `Turbo.session.drive = value` with `Turbo.config.drive = value`. The `Turbo.session.drive` property is deprecated and will be removed in a future version of Turbo.`"
+    )
+    config.drive.enabled = value
+  }
+
+  get progressBarDelay() {
+    return config.drive.progressBarDelay
+  }
+
+  set progressBarDelay(value) {
+    config.drive.progressBarDelay = value
+  }
+
+  get formMode() {
+    return config.forms.mode
+  }
+
+  set formMode(value) {
+    config.forms.mode = value
+  }
+
   // Private
 
   getActionForLink(link) {

src/tests/unit/export_tests.js

@@ -15,6 +15,7 @@ test("Turbo interface", () => {
   assert.equal(typeof Turbo.setConfirmMethod, "function")
   assert.equal(typeof Turbo.setFormMode, "function")
   assert.equal(typeof Turbo.cache, "object")
+  assert.equal(typeof Turbo.config, "object")
   assert.equal(typeof Turbo.cache.clear, "function")
   assert.equal(typeof Turbo.navigator, "object")
   assert.equal(typeof Turbo.session, "object")