fix(core): createModel to wrap class prototype methods as actions

[SisyphusZheng]

Fixes #983

Summary

createModel wraps model functions as actions via wrapInAction, which enumerates with for...in and therefore only sees own enumerable properties. Class instance models keep methods on the (non-enumerable) prototype, so they are missed entirely, while the public ValidateModel type accepts class instances. Consequences, all verified on main (b0df09a):

• two signal writes in a class method flush separately (the object-literal equivalent flushes once),
• an effect calling a class method that reads + writes a signal self-notifies until the Cycle detected guard throws,
• a getter returning a function crashes construction with a TypeError.

Changes

In wrapInAction:

• walk the prototype chain of "[object Object]"-tagged values and wrap inherited methods as own properties (skipping constructor and anything shadowed by an own property),
• skip accessor properties via property descriptors instead of reading and reassigning them (fixes the getter-only TypeError),
• the "[object Object]" check keeps built-ins (Map, Date, arrays, functions) untouched. This is defensive only — ValidateModel already rejects built-ins at the type level — but keeps JS users without typechecking safe.

Object-literal behavior is unchanged: all existing tests pass as-is.

Tests

Added to the createModel suite:

• class prototype methods get batched action semantics,
• methods inherited from a base class are wrapped,
• actions called inside effects stay untracked (no self-notify / Cycle detected),
• accessor properties no longer crash construction.

Verification

• pnpm vitest run packages/core — 172 passed, 2 skipped
• pnpm lint:tsc — clean
• pnpm oxlint packages/core/src/index.ts packages/core/test/signal.test.tsx — no new warnings beyond the file's pre-existing no-unused-expressions style

Includes a changeset for @preact/signals-core (patch).

AI assistance

This contribution was developed with assistance from OpenAI Codex.

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[changeset-bot]

🦋 Changeset detected

Latest commit: f66b612

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

Name	Type
@preact/signals-core	Patch
preact-signals-devtools	Patch

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[JoviDeCroock]

I'd like to mention that our code of conduct asks for LLM disclosure...

[JoviDeCroock]

The following compresses better

const wrapInAction = (value: Record<string, unknown>) => {
      for (
              let obj = value;
              obj && obj !== Object.prototype;
              obj =
                      Object.prototype.toString.call(value) === "[object Object]" &&
                      Object.getPrototypeOf(obj)
      ) {
              const descs = Object.getOwnPropertyDescriptors(obj);
              for (const key in descs) {
                      const val = descs[key].value;
                      if (typeof val === "function") {
                              if (key !== "constructor" && value[key] === val) {
                                      value[key] = action(val as (...args: unknown[]) => unknown);
                              }
                      } else if (
                              obj === value &&
                              typeof val === "object" &&
                              val !== null &&
                              !("brand" in val)
                      ) {
                              wrapInAction(val as Record<string, unknown>);
                      }
              }
      }
};

[SisyphusZheng]

I'd like to mention that our code of conduct asks for LLM disclosure...

Sorry, I missed the CoC requirement. I ran into this while integrating signals into a framework I'm working on. I used an LLM to help analyze the bug, draft the issue and PR description, and write the initial patch and tests. I reproduced all three failure modes myself, and I've applied your suggested change and re-ran the test suite locally.