[NullVoxPopuli-ai-agent]

RenderAdapter is a new interface that has every operation the VM does on the output tree. All code in @glimmer/runtime and @glimmer/node now calls it, and does not read or write a member of a node.

Start with packages/@glimmer/interfaces/lib/render-adapter.d.ts. It is the full interface in about 140 lines.

Names

A renderer and a render adapter are two different things:

• A renderer owns the roots and the render loop: BaseRenderer, the classic Renderer, and the one that renderComponent makes.
• A render adapter does the output operations for a renderer. RenderAdapter is the interface. DOMRenderAdapter implements it for the DOM. A terminal output would be a different adapter, with the same renderers.

Why

A different output, for example a terminal, needs one interface to implement. Before this PR, the VM called the DOM in two ways:

• Some calls went through DOMTreeConstruction and DOMChanges.
• About 100 other calls were direct, for example node.nextSibling, element.setAttribute(), and element[name] = value.

What the interface has

Group	Methods
Create	createElement, createElementNS, createTextNode, createComment
Change the tree	insertBefore, insertHTMLBefore, removeChild, clearChildren
Read the tree	parentNode, firstChild, lastChild, nextSibling, previousSibling, querySelector
Read a node	isNode, isFragment, isElement, isText, isComment, tagName, namespaceURI, nodeValue, setNodeValue
Attributes and properties	attributeNames, getAttribute, setAttribute, removeAttribute, hasProperty, getProperty, setProperty
Events	addEventListener, removeEventListener

The interface does not have getProp, toBool, toIterator, lookups, or managers. Those are the same for each output.

What uses it

• DOMRenderAdapter in @glimmer/runtime/lib/dom/render-adapter.ts is the adapter for a browser document and for a SimpleDOM document. It replaces DOMOperations, DOMTreeConstruction, and DOMChanges. NodeDOMRenderAdapter in @glimmer/node extends it.
• Environment#adapter holds the adapter. EnvironmentImpl and runtimeOptions take a RenderAdapter as argument 1.
• The client builder, the rehydration builder, the serialize builder, the updating VM, the dynamic attributes, the bounds helpers, and the on modifier all call env.adapter.
• BaseRenderer, BaseRenderer.strict, and the classic Renderer take a RenderAdapter.
• renderComponent accepts env.adapter. This is the Ember entry point for a different adapter.

Proof that the VM uses only the interface

packages/@glimmer-workspace/integration-tests/test/render-adapter-test.ts has a RenderAdapter on plain objects with no DOM member. A direct DOM access by the VM fails on these objects. The test calls Ember's renderComponent with env: { adapter }, and the run loop does the updates. It renders and updates:

• elements, static and dynamic attributes, and text
• {{#if}} and {{#each}}, with add, move, and remove
• the on modifier

Changes to private API

• Environment#adapter replaces getDOM() and getAppendOperations().
• EnvironmentImpl and runtimeOptions take a RenderAdapter in place of the EnvironmentOptions object. EnvironmentOptions (document, appendOperations, updateOperations) is removed.
• DOMRenderAdapter replaces DOMTreeConstruction and DOMChanges. NodeDOMRenderAdapter replaces NodeDOMTreeConstruction. The exports of @ember/-internals/glimmer have the new names.
• InternalModifierManager#create gets the environment as argument 5. The on modifier needs it.
• normalizeProperty, dynamicAttribute, clear, and move take the adapter as argument 1.
• sanitizeAttributeValue takes the tag name, not the element.
• BaseRenderer, BaseRenderer.strict, and the classic Renderer take a RenderAdapter in place of a document. Only the private env.document option of renderComponent still takes a document, and it becomes a DOMRenderAdapter before the renderer is made.

Not in this PR

• The classic Renderer (applications, {{outlet}}) makes its adapter from the -document service. Remove the service:-document registration #21772 removes that service.
• The node types are still SimpleNode and SimpleElement. A different adapter must cast its nodes.
• The rules for attribute against property, and the URL sanitization by tag name, stay in the VM. They are DOM rules.
• Classic Component (appendTo, readDOMAttr, this.element) and the event dispatcher call the DOM directly.
• isSerializationFirstNode and the debug checks in @glimmer/debug read nodeType and nodeValue directly.

Checks

• pnpm type-check and pnpm lint:eslint and pnpm lint:format pass.
• pnpm test passes: 9221 tests, 0 failures, 21 skipped.
• Performance is not measured. Each direct member access is now one method call on one class.

🤖 Generated with Claude Code

[NullVoxPopuli]

this is a lot 🙈