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text/1009-move-deprecation-workflow-to-apps.md

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+---
+stage: accepted
+start-date: 2024-02-22T00:00:00.000Z 
+release-date: # In format YYYY-MM-DDT00:00:00.000Z
+release-versions:
+teams: # delete teams that aren't relevant
+  - cli
+  - data
+  - framework
+  - learning
+  - typescript
+prs:
+  accepted: https://github.com/emberjs/rfcs/pull/1009 
+project-link:
+suite: 
+---
+
+<!--- 
+Directions for above: 
+
+stage: Leave as is
+start-date: Fill in with today's date, 2032-12-01T00:00:00.000Z
+release-date: Leave as is
+release-versions: Leave as is
+teams: Include only the [team(s)](README.md#relevant-teams) for which this RFC applies
+prs:
+  accepted: Fill this in with the URL for the Proposal RFC PR
+project-link: Leave as is
+suite: Leave as is
+-->
+
+# Move the deprecation workflow library to be installed in apps by default 
+
+## Summary
+
+Historically, folks have benefitted from [ember-cli-deprecation-workflow](https://github.com/mixonic/ember-cli-deprecation-workflow). This behavior is _so useful_, that it should be built in to folks applications by default.
+
+## Motivation
+
+Everyone needs a deprecation-workflow, and yet `ember-cli-deprecation-workflow` is not part of the default blueprint. 
+
+This RFC proposes how we can ship deprecation workflow handling behavior in apps by default, which may give us a blessed path for better integrating with build time deprecations as well (though that is not the focus of this RFC).
+
+
+## Detailed design
+
+
+Have `ember-cli-deprecation-workflow` installed by default.
+
+1. applications must have `@embroider/macros` installed by default.
+2. the app.js or app.ts can conditionally import a file which sets up the deprecation workflow 
+    ```diff app/app.js
+      import Application from '@ember/application';
+    + import { importSync, isDevelopingApp, macroCondition } from '@embroider/macros';
+
+      import loadInitializers from 'ember-load-initializers';
+      import Resolver from 'ember-resolver';
+      import config from 'test-app/config/environment';
+
+    + if (macroCondition(isDevelopingApp())) {
+    +   importSync('./deprecation-workflow');
+    + }
+
+      export default class App extends Application {
+        modulePrefix = config.modulePrefix;
+        podModulePrefix = config.podModulePrefix;
+        Resolver = Resolver;
+      }
+
+      loadInitializers(App, config.modulePrefix);
+    ```
+3. then in `app/deprecation-workflow.js` would use the already public API, 
+    ```js
+    import setupDeprecationWorkflow from 'ember-cli-deprecation-workflow';
+
+    setupDeprecationWorkflow({
+    /**
+        false by default, but if a developer / team wants to be more aggressive about being proactive with
+        handling their deprecations, this should be set to "true"
+    */
+      throwOnUnhandled: false,
+      handlers: [
+        /* ... handlers ... */
+      ]
+    });
+    ```
+
+
+This follows the README of [ember-cli-deprecation-workflow](https://github.com/ember-cli/ember-cli-deprecation-workflow?tab=readme-ov-file#getting-started).
+
+
+
+## How we teach this
+
+We'd want to add a new section in the guides under [`Application Concerns`](https://guides.emberjs.com/release/applications/) that talks about deprecations, how and how to work through those deprecations.
+
+All of this content already exists using a similar strategy as above, here, [under "Configuring Ember"](https://guides.emberjs.com/release/configuring-ember/handling-deprecations/#toc_deprecation-workflow), and also walks through how to use `ember-cli-deprecation-workflow`. 
+
+This README of [ember-cli-deprecation-workflow](https://github.com/ember-cli/ember-cli-deprecation-workflow?tab=readme-ov-file#getting-started) also explains, in detail, how to use this tool / workflow, and that content can be copied in to the guides.
+
+## Drawbacks
+
+For older projects, this could be _a_ migration. But as it is additional blueprint boilerplate, it is optional.
+
+## Alternatives
+
+There are only a few features of `ember-cli-deprecation-workflow` that we need to worry about:
+- enabled or not - do we check deprecations at all, or ignore everything (current default)
+- `throwOnUnhandled` - this is the most aggressive way to stay on top of your deprecations, but can be frustrating for folks who may not be willing to fix things in `node_modules` when new deprecations are introduced.
+
+- `window.flushDeprecations()` - prints the list of deprecations encountered since the last page refresh
+- Matchers - a fuzzier way to match deprecation messages rather than strictly matching on the deprecation id (sometimes deprecation messages have information about surrounding / relevant context, and these could be used to more fine-grainedly work through large-in-numbers deprecations)
+- Logging / Ignoring / Throwing - when encountering a matched deprecation (whether by id or by regex, how should it be handled?)
+
+
+However, folks can get a basic deprecation-handling workflow going in their apps without the above features,
+
+1. applications must have `@embroider/macros` installed by default.
+2. the app.js or app.ts can conditionally import a file which sets up the deprecation workflow 
+    ```diff app/app.js
+      import Application from '@ember/application';
+    + import { importSync, isDevelopingApp, macroCondition } from '@embroider/macros';
+
+      import loadInitializers from 'ember-load-initializers';
+      import Resolver from 'ember-resolver';
+      import config from 'test-app/config/environment';
+
+    + if (macroCondition(isDevelopingApp())) {
+    +   importSync('./deprecation-workflow');
+    + }
+
+      export default class App extends Application {
+        modulePrefix = config.modulePrefix;
+        podModulePrefix = config.podModulePrefix;
+        Resolver = Resolver;
+      }
+
+      loadInitializers(App, config.modulePrefix);
+    ```
+    this conditional import is now easily customizable for folks in their apps, so they could opt to _not_ strip deprecation messages in production, and see where deprecated code is being hit by users (reported via Sentry, BugSnag, or some other reporting tool) -- which may be handy for folks who have a less-than-perfect test suite (tests being the only current way to automatically detect where deprecated code lives).
+3. the `app/deprecation-workflow.js` would use the already public API, [`registerDeprecationHandler`](https://api.emberjs.com/ember/5.6/functions/@ember%2Fdebug/registerDeprecationHandler)
+    ```ts
+    import { registerDeprecationHandler } from '@ember/debug';
+
+    import config from '<app-moduleName>/config/environment';
+
+    const SHOULD_THROW = config.environment !== 'production';
+    const SILENCED_DEPRECATIONS: string[] = [
+      // Add ids of deprecations you temporarily want to silence here.
+    ];
+
+    registerDeprecationHandler((message, options, next) => {
+      if (!options) {
+        console.error('Missing options');
+        throw new Error(message);
+      }
+
+      if (SILENCED_DEPRECATIONS.includes(options.id)) {
+        return;
+      } else if (SHOULD_THROW) {
+        throw new Error(message);
+      }
+
+      next(message, options);
+    });
+    ```
+
+
+This simple implementation of deprecation workflow may work for libraries' test-apps, but it is not as robust as what `ember-cli-deprecation-workflow` offers, per the above-listed set of features that folks are used to.
+
+To get all of those features from `ember-cli-deprecation-workflow`, we could define a function, `setupDeprecationWorkflow`, taken from the [Modernization PR on ember-cli-deprecation-workflow](https://github.com/mixonic/ember-cli-deprecation-workflow/pull/159), this is what the deprecation-workflow file could look like:
+
+<details><summary>ember-cli-deprecation-workflow/index.js</summary>
+
+```js
+import { registerDeprecationHandler } from '@ember/debug';
+
+const LOG_LIMIT = 100;
+
+export default function setupDeprecationWorkflow(config) {
+  self.deprecationWorkflow = self.deprecationWorkflow || {};
+  self.deprecationWorkflow.deprecationLog = {
+    messages: {},
+  };
+
+  registerDeprecationHandler((message, options, next) =>
+    handleDeprecationWorkflow(config, message, options, next),
+  );
+
+  registerDeprecationHandler(deprecationCollector);
+
+  self.deprecationWorkflow.flushDeprecations = flushDeprecations;
+}
+
+let preamble = `import setupDeprecationWorkflow from 'ember-cli-deprecation-workflow';
+
+setupDeprecationWorkflow({
+  workflow: [
+`;
+
+let postamble = `  ]
+});`;
+
+export function detectWorkflow(config, message, options) {
+  if (!config || !config.workflow) {
+    return;
+  }
+
+  let i, workflow, matcher, idMatcher;
+  for (i = 0; i < config.workflow.length; i++) {
+    workflow = config.workflow[i];
+    matcher = workflow.matchMessage;
+    idMatcher = workflow.matchId;
+
+    if (typeof idMatcher === 'string' && options && idMatcher === options.id) {
+      return workflow;
+    } else if (typeof matcher === 'string' && matcher === message) {
+      return workflow;
+    } else if (matcher instanceof RegExp && matcher.exec(message)) {
+      return workflow;
+    }
+  }
+}
+
+export function flushDeprecations() {
+  let messages = self.deprecationWorkflow.deprecationLog.messages;
+  let logs = [];
+
+  for (let message in messages) {
+    logs.push(messages[message]);
+  }
+
+  let deprecations = logs.join(',\n') + '\n';
+
+  return preamble + deprecations + postamble;
+}
+
+export function handleDeprecationWorkflow(config, message, options, next) {
+  let matchingWorkflow = detectWorkflow(config, message, options);
+  if (!matchingWorkflow) {
+    if (config && config.throwOnUnhandled) {
+      throw new Error(message);
+    } else {
+      next(message, options);
+    }
+  } else {
+    switch (matchingWorkflow.handler) {
+      case 'silence':
+        // no-op
+        break;
+      case 'log': {
+        let key = (options && options.id) || message;
+
+        if (!self.deprecationWorkflow.logCounts) {
+          self.deprecationWorkflow.logCounts = {};
+        }
+
+        let count = self.deprecationWorkflow.logCounts[key] || 0;
+        self.deprecationWorkflow.logCounts[key] = ++count;
+
+        if (count <= LOG_LIMIT) {
+          console.warn('DEPRECATION: ' + message);
+          if (count === LOG_LIMIT) {
+            console.warn(
+              'To avoid console overflow, this deprecation will not be logged any more in this run.',
+            );
+          }
+        }
+
+        break;
+      }
+      case 'throw':
+        throw new Error(message);
+      default:
+        next(message, options);
+        break;
+    }
+  }
+}
+
+export function deprecationCollector(message, options, next) {
+  let key = (options && options.id) || message;
+  let matchKey = options && key === options.id ? 'matchId' : 'matchMessage';
+
+  self.deprecationWorkflow.deprecationLog.messages[key] =
+    '    { handler: "silence", ' + matchKey + ': ' + JSON.stringify(key) + ' }';
+
+  next(message, options);
+}
+```
+
+</details>
+
+and at this point, we may as well build it into `ember` and not use an additional library at all, **and this is what the primary proposal of this RFC: build the deprecation workflow setup function in to ember**, so re-running through the setup steps:
+
+1. applications must have `@embroider/macros` installed by default.
+2. the app.js or app.ts can conditionally import a file which sets up the deprecation workflow 
+    ```diff app/app.js
+      import Application from '@ember/application';
+    + import { importSync, isDevelopingApp, macroCondition } from '@embroider/macros';
+
+      import loadInitializers from 'ember-load-initializers';
+      import Resolver from 'ember-resolver';
+      import config from 'test-app/config/environment';
+
+    + if (macroCondition(isDevelopingApp())) {
+    +   importSync('<app-moduleName>/deprecation-workflow');
+    + }
+
+      export default class App extends Application {
+        modulePrefix = config.modulePrefix;
+        podModulePrefix = config.podModulePrefix;
+        Resolver = Resolver;
+      }
+
+      loadInitializers(App, config.modulePrefix);
+    ```
+    this conditional import is now easily customizable for folks in their apps, so they could opt to _not_ strip deprecation messages in production, and see where deprecated code is being hit by users (reported via Sentry, BugSnag, or some other reporting tool) -- which may be handy for folks who have a less-than-perfect test suite (tests being the only current way to automatically detect where deprecated code lives).
+3. the `app/deprecation-workflow.js` would use the already public API, [`registerDeprecationHandler`](https://api.emberjs.com/ember/5.6/functions/@ember%2Fdebug/registerDeprecationHandler)
+    ```js
+    import { setupDeprecationWorkflow } from '@ember/debug';
+
+    setupDeprecationWorkflow({
+      throwOnUnhandled: true,
+      handlers: [
+        /* ... handlers ... */
+      ]
+    });
+    ```
+
+
+
+## Unresolved questions
+
+n/a