Sylvain Duchesne
53 lines
5.9 KiB
Markdown
53 lines
5.9 KiB
Markdown
---
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type: bug
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summary: A live read through the published `useShape` never starts against a broker deployed before `orm_start` was renamed `orm_start_graph` — it stays empty and pending forever, with one console error as the only trace
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severity: major
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opened: 2026-08-17
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last_checked: 2026-08-17
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---
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# `useShape` opens no live read against the deployed broker
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The published `useShape` is a passthrough to `@ng-org/orm`'s hook (`packages/polyfill/src/surface/use-shape.ts`) — this package adds the read filter and forwards. Against the broker deployed today, the subscription that hook opens **never starts**: its set stays empty, its readiness never settles, no engine update ever arrives, and the only trace is one `console.error`. An application sees "this scope holds nothing", indefinitely, which is the exact confusion the rest of the read surface is built to prevent.
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The cause is upstream, in NextGraph. **Nothing in this package can work around it** — the failure is a name lookup two hops below our surface.
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## The mechanism — one method name, kept in three places by hand
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VERIFIED 2026-08-17 by reading `/home/sylvain/projects/nextgraph/nextgraph-rs` at `213338f6`.
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A live ORM read is one call, and it is streamed: the engine pushes into a callback rather than answering once. Nothing in the transport infers that — each hop looks the method up in a **hand-maintained table** mapping method name to the index of its callback argument, and a method missing from the table takes the plain request/response branch instead.
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1. `sdk/js/orm/src/connector/GraphOrmSubscription.ts` — the `OrmSubscription` constructor is the only place a live graph read begins: `ng.orm_start_graph(scope.graphs, scope.subjects, shapeType, session.session_id, this.onBackendMessage)`. Five arguments, callback last. `useShape` reaches it through `OrmSubscription.getOrCreate` (`sdk/js/orm/src/frontendAdapters/react/useShape.ts`).
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2. `sdk/js/web/src/index.ts` — the application-side `ng` proxy. `streamed_api` must contain the method, or `rpc` posts the arguments verbatim to the parent window, callback included. A function is not structured-cloneable, so that post throws.
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3. `sdk/js/api-web/main.ts` — the broker-side proxy, an independent copy of the same table. Same fallback into `myWorker.postMessage`, same throw.
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The hops between the two tables carry no table of their own and cannot repair a mismatch: `infra/ngnet/auth/src/main.ts` forwards `{method, args, streamed, port}` unchanged, and `engine/broker/auth/src/App.svelte` re-appends a callback **only** when `streamed` is true.
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**The name changed.** Both tables keyed the method as `orm_start` until commit `d5ecd0fd` (2026-01-16, "refactor discrete orm for yjs") renamed it to `orm_start_graph` in both files at once — while the ORM had been calling `orm_start_graph`. A build made before that commit therefore does not recognise the method a live read needs.
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**The application side is already correct**, and that is what isolates the defect. This package pins `@ng-org/web@0.1.2-alpha.13` (`packages/polyfill/package.json`), which is the version at `213338f6` — the rename is in it. `@ng-org/api-web` is `private: true` and has never been version-bumped past `0.1.2`: it is **not published**, it ships only inside the broker build. Its table is whatever the operator last deployed, and no consumer can pin it.
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**Why it fails in silence:** `orm_start_graph` is awaited inside a `try` whose `catch` is `console.error(e)`, and `resolveReady()` is called on one path only — the arrival of initial data. A rejected start leaves the readiness promise pending forever and the set permanently empty. This is the same upstream property already recorded in `docs/api-contract.md` (a failed read *is* an eternal pending upstream), reached here through a different door.
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## What is affected, and what is not
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- **Affected:** the published `useShape`, and only it.
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- **Not affected:** `watchShape`, `subscribeDoc`, `subscribeDocs`, `readUnion`. These open one `doc_subscribe` per document, and `doc_subscribe: 2` has been in both tables continuously under a stable name. `watchShape` is built on that path, not on the ORM subscription — it is a working reactive read today.
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That is why the library's own suites and the reference application do not show it: nothing in this package calls `useShape` internally.
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## Not verified
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The deployed broker's table was **not read**. `https://nextgraph.net/redir/` returns a page containing none of the protocol markers, so it is not the bundle that holds it, and probing further was out of mandate. What is established is the mechanism and its exact precondition — a broker built before `d5ecd0fd` — not that the running deployment sits before it. The symptom was reported by the consuming application, not reproduced here.
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## What to do
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- **Do not build on live `useShape`.** Use `watchShape` for a reactive read, `readUnion` for a one-shot one. This is stated in the contract's `## Non-guarantees` so a consumer meets it without reading this leaf.
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- **The fix is not ours.** It is a NextGraph deployment: rebuild and redeploy the broker from a source at or after `d5ecd0fd`. Nothing to change in this repository, and nothing to open upstream from here — report it, do not patch around it.
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- **To check whether it is closed:** open a live `useShape` against the deployment and watch for an initial payload. A permanently empty set with one `console.error` naming `orm_start_graph` means the table is still stale.
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## The shape worth remembering
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A method name duplicated across three independently-deployed artifacts, with a **silent** fallback when they disagree, is a defect that cannot be caught by any one repository's tests. Renaming it in the two tables in one commit fixed the source; it did not fix anything already running. Anything this package routes through a streamed method inherits the same exposure — that is the reason `subscribeDocs` composing per-document `doc_subscribe` is worth more than it looks.
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