Deprecate Ember Vendor Bundles

text/1101-deprecate-ember-vendor-bundles.md

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+---
+stage: accepted
+start-date: 2025-05-13T00:00:00.000Z
+release-date: # In format YYYY-MM-DDT00:00:00.000Z
+release-versions:
+teams: # delete teams that aren't relevant
+  - cli
+  - framework
+  - learning
+prs:
+  accepted: https://github.com/emberjs/rfcs/pull/1101
+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
+-->
+
+<!-- Replace "RFC title" with the title of your RFC -->
+
+# Deprecate Ember Vendor Bundles
+
+## Summary
+
+The published `ember-source` package contains several AMD-specific bundled builds
+of Ember that are appended to `vendor.js` in the classic build system. 
+This RFC deprecates the following files:
+
+- `ember.debug.js`
+- `ember.prod.js`
+- `ember-testing.js`
+- `ember-template-compiler.js`
+
+Instead, Ember will be included in application builds as ES module library via `ember-auto-import`.
+
+## Motivation
+
+Maintaining the legacy AMD-specific bundled copies of Ember is no longer necessary. 
+Modern Ember applications should consume Ember as ES modules, which aligns with 
+the broader JavaScript ecosystem. This change simplifies the build pipeline and 
+reduces maintenance overhead.
+
+This deprecation will have no effect on applications using Embroider with 
+`staticEmberSource: true` or Embroider v4 (Vite). It only impacts applications 
+using the classic build system without Embroider.
+
+## Transition Path
+
+> This is the bulk of the RFC.
+
+> Explain the design in enough detail for somebody
+> familiar with the framework to understand, and for somebody familiar with the
+> implementation to implement. This should get into specifics and corner-cases,
+> and include examples of how the feature is used. Any new terminology should be
+> defined here.
+
+> Please keep in mind any implications within the Ember ecosystem, such as:
+>
+> - Lint rules (ember-template-lint, eslint-plugin-ember) that should be added, modified or removed
+> - Features that are replaced or made obsolete by this feature and should eventually be deprecated
+> - Ember Inspector and debuggability
+> - Server-side Rendering
+> - Ember Engines
+> - The Addon Ecosystem
+> - IDE Support
+> - Blueprints that should be added or modified
+
+
+### Classic Build System
+
+We will introduce a new optional feature for projects to opt into consuming 
+Ember as ES modules. Not having this optional feature enabled will result in 
+a deprecation warning.
+
+Addons that rely on accessing Ember from `treeForVendor` or on accessing Ember
+from vendor will need to update their implementation. 
+
+### Embroider v4 or with `staticEmberSource: true`
+
+This deprecation will have no effect on these projects. They already consume Ember as ES modules.
+
+## How we teach this
+
+> What names and terminology work best for these concepts and why? How is this
+> idea best presented? As a continuation of existing Ember patterns, or as a
+> wholly new one?
+
+> Would the acceptance of this proposal mean the Ember guides must be
+> re-organized or altered? Does it change how Ember is taught to new users
+> at any level?
+
+> How should this feature be introduced and taught to existing Ember
+> users?
+
+> Keep in mind the variety of learning materials: API docs, guides, blog posts, tutorials, etc.
+
+### Deprecation Guide
+
+Ember will no longer publish legacy AMD-specific Ember builds. To opt-in to 
+consuming Ember as ES modules and clear this deprecation, enable the 
+`ember-modules` optional feature by running `ember feature:enable ember-modules`.
+
+This applies only to the classic build system or to Embroider < 4.0 without the
+`staticEmberSource: true` option. If you see this deprecation warning in these 
+setups, please [open an issue](https://github.com/emberjs/ember.js/issues/new/choose).
+
+Alternatively, you can also clear the deprecation by moving to Embroider v4 by 
+running the [Ember Vite Codemod](https://github.com/mainmatter/ember-vite-codemod),
+but this may require additional changes to your project. 
+
+The AMD-specific Ember builds will no longer be published in next Ember major release 
+and no longer be bundled into `vendor.js`, even on the classic build system. These files are:
+- 
+- `ember.debug.js`
+- `ember.prod.js`
+- `ember-testing.js`
+- `ember-template-compiler.js`
+
+- In rare cases, Addons were relying on accessing Ember from `vendor`. If you have 
+addons that do so they will need to be updated to consume Ember as ES modules.
+
+A known addon that previously relied on accessing Ember from `vendor` is 
+[ember-cli-deprecation-workflow](https://github.com/ember-cli/ember-cli-deprecation-workflow). 
+Please ensure you are on the latest version of this addon as that reliance has 
+been removed.
+
+## Drawbacks
+
+> Why should we _not_ do this? Please consider the impact on teaching Ember,
+> on the integration of this feature with other existing and planned features,
+> on the impact of the API churn on existing apps, etc.
+
+> There are tradeoffs to choosing any path, please attempt to identify them here.
+
+## Alternatives
+
+> What other designs have been considered? What is the impact of not doing this?
+
+> This section could also include prior art, that is, how other frameworks in the same domain have solved this problem.
+
+## Unresolved questions
+
+> Optional, but suggested for first drafts. What parts of the design are still
+> TBD?