Bug 1539764 - Add a targetFront attribute to the Front class to retrieve the target front. r=ochameau

Differential Revision: https://phabricator.services.mozilla.com/D39130

--HG--
extra : moz-landing-system : lando

devtools/client/framework/test/browser_target_get-front.js

@@ -3,8 +3,8 @@
 
 add_task(async function() {
   gBrowser.selectedTab = BrowserTestUtils.addTab(gBrowser);
-  const tab = await addTab("about:blank");
 
+  const tab = await addTab("about:blank");
   const target = await TargetFactory.forTab(tab);
   await target.attach();
 
@@ -12,6 +12,14 @@ add_task(async function() {
   const target2 = await TargetFactory.forTab(tab2);
   await target2.attach();
 
+  info("Test the targetFront attribute for the root");
+  const { client } = target;
+  is(
+    client.mainRoot.targetFront,
+    null,
+    "got null from the targetFront attribute for the root"
+  );
+
   info("Test getting a front twice");
   const getAccessibilityFront = await target.getFront("accessibility");
   const getAccessibilityFront2 = await target.getFront("accessibility");
@@ -20,6 +28,16 @@ add_task(async function() {
     getAccessibilityFront2,
     "got the same front when calling getFront twice"
   );
+  is(
+    getAccessibilityFront.targetFront,
+    target,
+    "got the correct targetFront attribute from the front"
+  );
+  is(
+    getAccessibilityFront2.targetFront,
+    target,
+    "got the correct targetFront attribute from the front"
+  );
 
   info("Test getting a front on different targets");
   const target1Front = await target.getFront("accessibility");
@@ -29,6 +47,16 @@ add_task(async function() {
     true,
     "got different fronts when calling getFront on different targets"
   );
+  is(
+    target1Front.targetFront !== target2Front.targetFront,
+    true,
+    "got different targetFront from different fronts from different targets"
+  );
+  is(
+    target2Front.targetFront,
+    target2,
+    "got the correct targetFront attribute from the front"
+  );
 
   info("Test async front retrieval");
   // use two fronts that are initialized one after the other.

devtools/shared/fronts/targets/target-mixin.js

@@ -202,7 +202,8 @@ function TargetMixin(parentClass) {
       this._inspector = await getFront(
         this.client,
         "inspector",
-        this.targetForm
+        this.targetForm,
+        this
       );
       this.emit("inspector", this._inspector);
       return this._inspector;
@@ -229,7 +230,7 @@ function TargetMixin(parentClass) {
       ) {
         return front;
       }
-      front = getFront(this.client, typeName, this.targetForm);
+      front = getFront(this.client, typeName, this.targetForm, this);
       this.fronts.set(typeName, front);
       // replace the placeholder with the instance of the front once it has loaded
       front = await front;

devtools/shared/protocol/Front.js

@@ -40,6 +40,9 @@ class Front extends Pool {
   constructor(conn = null) {
     super(conn);
     this.actorID = null;
+    // The targetFront attribute represents the debuggable context. Only target-scoped
+    // fronts and their children fronts will have the targetFront attribute set.
+    this.targetFront = null;
     this._requests = [];
 
     // Front listener functions registered via `onFront` get notified

devtools/shared/protocol/types.js

@@ -317,7 +317,6 @@ types.addActorType = function(name) {
       let front = ctx.conn.getActor(actorID);
       if (!front) {
         // If front isn't instantiated yet, create one.
-
         // Try lazy loading front if not already loaded.
         // The front module will synchronously call `FrontClassWithSpec` and
         // augment `type` with the `frontClass` attribute.
@@ -330,7 +329,11 @@ types.addActorType = function(name) {
         const Class = type.frontClass;
         front = new Class(ctx.conn);
         front.actorID = actorID;
-        ctx.marshallPool().manage(front);
+        const parentFront = ctx.marshallPool();
+        // If this is a child of a target-scoped front, propagate the target front to the
+        // child front that it manages.
+        front.targetFront = parentFront.targetFront;
+        parentFront.manage(front);
       }
 
       // When the type `${name}#actorid` is used, `v` is a string refering to the
@@ -490,8 +493,11 @@ exports.registerFront = function(cls) {
  * @param json form
  *    If we want to instantiate a global actor's front, this is the root front's form,
  *    otherwise we are instantiating a target-scoped front from the target front's form.
+ * @param [Target|null] target
+ *    If we are instantiating a target-scoped front, this is a reference to the front's
+ *    Target instance, otherwise this is null.
  */
-function getFront(client, typeName, form) {
+function getFront(client, typeName, form, target = null) {
   const type = types.getType(typeName);
   if (!type) {
     throw new Error(`No spec for front type '${typeName}'.`);
@@ -503,6 +509,8 @@ function getFront(client, typeName, form) {
   // a capital letter for all constructors.
   const Class = type.frontClass;
   const instance = new Class(client);
+  // Set the targetFront for target-scoped fronts.
+  instance.targetFront = target;
   const { formAttributeName } = instance;
   if (!formAttributeName) {
     throw new Error(`Can't find the form attribute name for ${typeName}`);