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+# Commands
+
+Commands are singletons, which can be easily used by any frontend code.
+They are meant to be exposed widely to the frontend so that any code can easily call any of their methods.
+
+Commands classes expose static methods, which:
+* route to the right Front/Actor's method
+* handle backward compatibility
+* map to many target's actor if needed
+
+These classes are instantiated once per descriptor
+and may have inner state, emit events, fire callbacks,...
+
+A transient backward compat need, required by Fission refactorings will be to have some code checking a trait, and either:
+* call a single method on a parent process actor (like BreakpointListActor.setBreakpoint)
+* otherwise, call a method on each target's scoped actor (like ThreadActor.setBreakpoint, that, for each available target)
+
+Without such layer, we would have to put such code here and there in the frontend code.
+This will be harder to remove later, once we get rid of old pre-fission-refactoring codepaths.
+
+This layer already exists in some panels, but we are using slightly different names and practices:
+* Debugger uses "client" (devtools/client/debugger/src/client/) and "commands" (devtools/client/debugger/src/client/firefox/commands.js)
+ Debugger's commands already bundle the code to dispatch an action to many target's actor.
+ They also contain some backward compat code.
+ Today, we pass around a `client` object via thunkArgs, which is mapped to commands.js,
+ instead we could pass a debugger command object.
+* Network Monitor uses "connector" (devtools/client/netmonitor/src/connector)
+ Connectors also bundles backward compat and dispatch to many target's actor.
+ Today, we pass the `connector` to all middlewares from configureStore,
+ we could instead pass the netmonitor command object.
+* Web Console has:
+ * devtools/client/webconsole/actions/input.js:handleHelperResult(), where we have to put some code, which is a duplicate of Netmonitor Connector,
+ and could be shared via a netmonitor command class.
+* Inspector is probably the panel doing the most dispatch to many target's actor.
+ Codes using getAllInspectorFronts could all be migrated to an inspector command class:
+ https://searchfox.org/mozilla-central/search?q=symbol:%23getAllInspectorFronts&redirect=false
+ and simplify a bit the frontend.
+ It is also one panel, which still register listener to each target's inspector/walker fronts.
+ Because inspector isn't using resources.
+ But this work, registering listeners for each target might be done by such layer and translate the many actor's event into a unified one.
+
+Last, but not least, this layer may allow us to slowly get rid of protocol.js.
+Command classes aren't Fronts, nor are they particularly connected to protocol.js.
+If we make it so that all the Frontend code using Fronts uses Commands instead, we might more easily get away from protocol.js.