ClassHierarchy.isA answers false for ancestors above Neo.component.Base

Welcome 👋

Every Neo class knows its parent, and Neo.manager.ClassHierarchy.isA(descendant, ancestor) answers "does this class extend that one?" by walking up that chain. It has a small bug, and fixing it is a good first PR: one method, a failing test first, then the fix.

This is a good first issue for Hacktoberfest 2026. It needs Node.js and a clone of this repository: no Docker, no AI setup.

[!IMPORTANT] Reserved for first-time Neo.mjs contributors. The maintainer team will not claim, edit, or implement this issue through 2026-10-31. Comment here to claim it, and ask anything on this issue.

Set up once: follow Set up the engine from a clone, including npm run bundle-browser-deps: without it the unit suite selects zero tests.

The bug

isA() stops walking as soon as it reaches Neo.component.Base, unless the ancestor asked about is Neo.core.Base. That shortcut assumed nothing sits between the two. Since then, Neo.component.Base extends Neo.component.Abstract, so the shortcut now hides a real ancestor. Measured on dev (2026-09-23):

ClassHierarchy.get('Neo.component.Base').parentClassName is 'Neo.component.Abstract'.

Where things live

• Source: src/manager/ClassHierarchy.mjs, method isA()
• New test file: test/playwright/unit/manager/ClassHierarchy.spec.mjs
• Pattern to copy: test/playwright/unit/manager/Instance.spec.mjs (the setup() call and imports). Import src/button/Base.mjs in the spec so the button classes are registered.

Done when

• The spec is written first and fails on the Neo.component.Abstract case: paste that failing output in your PR.
• isA() no longer stops early at Neo.component.Base: the walk ends at Neo.core.Base anyway, and the answer cache (isAQueryMap) stays.
• The spec also covers: a class against itself (true), a direct parent, an unrelated class (false), and a second identical call returning the same answer.
• npm run test-unit -- test/playwright/unit/manager/ClassHierarchy.spec.mjs passes.
• npm run test-unit passes.

Out of scope

Other ClassHierarchy methods, and mixins (they are not in the parent chain).

While you wait for review

You just pinned one small piece of a multi-threaded application engine: in Neo.mjs your app's code runs inside a web worker, and the main thread only paints. Two things worth ten minutes:

• See the part nobody expects. Run npm run build-themes -- -n -e dev -t all and npm run server-start, open apps/workstation/, and drag a tab out of the browser window. It becomes its own OS window, still running, with the same component instances and the same worker. Benefits: Introduction explains why that is possible.
• Your coding agent can go much further here. The skills this repository's AI maintainers work with are published on npm as NEO_INLINE_CODE_38, and they need no Knowledge Base and no Memory Core. With Claude or GPT beside you, the help wanted issues are within reach after this one.