compilePackages: inline `export default class Name { … }` (ESM) drops the prototype method table — only `constructor` survives (ESM sibling of #4933; blocks ink render)

[proggeramlug]

Summary

An inline export default class Name { … } declaration in a compilePackages (ESM) module loses its entire method table: Class.prototype ends up with only constructor. All prototype methods and class-field initializers are dropped, so instances have none of their methods.

The equivalent class written as a named declaration then default-exported works fine. So this is purely the inline export default class emit path — the ESM sibling of #4933 (module.exports = class, fixed in #4947 for CJS).

Minimal repro

node_modules/edcpkg/index.js ("type":"module", in perry.compilePackages + allow.compilePackages):

export default class Widget {
  field1;
  arrow = () => 'arrow';
  greet() { return 'hello'; }
}

node_modules/edcpkg2/index.js:

class Widget2 { greet() { return 'hi2'; } }
export default Widget2;     // named, then default-export

import Widget from 'edcpkg';
import Widget2 from 'edcpkg2';
console.log(Object.getOwnPropertyNames(Widget.prototype), typeof Widget.prototype.greet);
console.log(Object.getOwnPropertyNames(Widget2.prototype), typeof Widget2.prototype.greet);

Output:

export default class Widget:   proto keys = constructor            | greet = undefined   ✗
                               new Widget().greet = undefined  arrow = undefined         ✗
class X; export default X:     proto keys = constructor,greet      | greet = function    ✓

Node prints constructor,greet / function for both. User-code (non-compilePackages) classes of every shape (methods-only, bare-field+method, arrow-field+method, mixed) all work — confirmed — so the trigger is specifically inline export default class inside a compiled package.

How it surfaced (ink, #348)

This is the first render-execution wall (the React hook-dispatcher #4950 is fixed; full init + render() now run). ink/build/ink.js:128 is export default class Ink { … render(node){…} … }. Under Perry Ink.prototype = {constructor} only, so ink's render() does:

const instance = new Ink(inkOptions);
instance.render(node);   // TypeError: render is not a function

Confirmed via a runtime probe at that call site: Ink.prototype = object, Ink.prototype.render = undefined, ownKeys(proto) = ['constructor'].

Scope / suggested fix

• Mirror the fix(cjs_wrap): flat-emit module.exports = <Class> that closes over a top-level binding (#4933) #4947 fix for the ESM side: emit export default class Name { … } by lowering it to a named class declaration whose methods/field-initializers are installed normally, then make the default export bind that class — rather than the current path that publishes a bare constructor with an empty prototype.
• Both prototype methods and class-field initializers are dropped (the repro's greet method and arrow/field1 fields all vanish), so the fix needs to cover the full class-body installation, not just methods.

Impact

• Any compilePackages module using export default class { … } — an extremely common authoring style (ink, and many others).
• ink end-to-end (Compile ink (React-based TUI framework) end-to-end via perry.compilePackages #348): blocks instance.render(). After it, ink's next gate is yoga-layout's WASM runtime (out-of-scope).

Related

• compilePackages: module.exports = class loses the class method table — static AND prototype methods read undefined (breaks stack-utils → ink) #4933 / fix(cjs_wrap): flat-emit module.exports = <Class> that closes over a top-level binding (#4933) #4947 (CJS module.exports = class method-table loss — same bug, CJS form)
• Compile ink (React-based TUI framework) end-to-end via perry.compilePackages #348 (ink end-to-end), compilePackages: cross-module mutable object loses identity — react-reconciler's ReactSharedInternals.H dispatcher invisible to react → 'Invalid hook call' null dispatcher (blocks all React renderers) #4950/fix(hir,codegen,runtime): clear the #4950 React render-time walls (JSX createElement mode + 4 companion fixes) #4969 (the render-time walls cleared to reach this)