Deprecate string based actions

text/0632-deprecate-string-based-actions.md

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+- Start Date: 2020-05-23
+- Relevant Team(s): Ember.js
+- RFC PR: https://github.com/emberjs/rfcs/pull/632
+- Tracking: (leave this empty)
+
+# Deprecate String Based Actions
+
+## Motivation
+
+> In Ember 1.13 we introduced [closure actions](https://github.com/emberjs/rfcs/blob/00ac2685c86f27d41547012903f485a4ef338d27/active/0000-improved-actions.md), which have been recommended over string based actions. This officially deprecates string based actions in favor of closure actions,
+which provide many benefits such as
+
+1. simpler passing through components
+2. less need for an actions hash
+3. ability to return a value
+4. typing in TypeScript
+5. more in line with the Octane programming model
+
+## Detailed Design
+
+We will deprecate the following:
+
+1. The `send` api.
+2. The use of a string parameter to the `action` helper.
+3. The use of a string parameter to the `action` modifier.
+
+The `send` api may currently be used in components, controllers, and routes.
+It is used to target the `actions` hash. In calling the `actions` hash of the
+same object, `send` can be replaced by a function call once the method is
+moved outside the `actions` hash.
+
+For cases where `send` is used to go from a controller to a route or from
+a route to a parent route, no direct replacement for this "action bubbling"
+behavior will be provided.
+Instead, users are recommended to inject the router service.
+
+## Transition Path
+
+Users will transition to closure actions.
+
+While the action helper and modifiers are still supported with non-string arguments, the refactoring recommendation is to switch to the on modifier and @action decorator directly. It is possible that the action helpers and modifiers will be deprecated in future RFCs.
+
+For example, take this button that sends the foo action with the default click event:
+
+```js
+export default Component.extend({
+    someMethod() {
+        this.send('actionName');
+    },
+
+    actions: {
+        actionName() {
+            // do something
+        }
+    }
+});
+```
+
+```hbs
+<button {{action 'actionName'}}>Action Label</button>
+```
+
+Although this could be refactored to:
+
+
+```js
+export default Component.extend({
+    someMethod() {
+        this.actionName();
+    },
+
+    actionName() {
+        // do something
+    }
+});
+```
+
+```hbs
+<button {{action this.actionName}}>Action Label</button>
+```
+
+it is recommended that the code is refactored instead to:
+
+```js
+export default Component.extend({
+    someMethod() {
+        this.actionName();
+    },
+
+    actionName: action(function() {
+        // do something
+    })
+});
+```
+
+```hbs
+<button {{on "click" this.actionName}}>Action Label</button>
+```
+
+so that it can eventually become:
+
+```js
+export class extends Component {
+    someMethod() {
+        this.actionName();
+    }
+
+    @action
+    actionName() {
+        // do something
+    }
+}
+```
+
+```hbs
+<button {{on "click" this.actionName}}>Action Label</button>
+```
+
+## How We Teach This
+
+> We already teach closure actions exclusively in the guides. Other than a new
+deprecation guide, no additional material should be necessary.
+
+## Drawbacks
+
+> Some older applications have thousands of string based actions throughout their codebases.
+We should consider writing a codemod to ease the transition.
+
+## Alternatives
+
+> Closure actions are now the standard in Ember, so other alternatives have not been
+seriously considered.
+
+## Unresolved questions
+
+> Can we also deprecate the use of the `actions` hash? Can we also deprecate using `this.actions`?
+Can the `target` property of `@ember/controller` and `@ember/component` be deprecated?