`ObjectMap`'s `dataConfig` pays a `JSON.stringify` on every render to buy an identity that `[schema]` already gives for free

[yinlianghui]

Measured while implementing #5976 (PR #6016). Out of that card's scope — filing plainly for triage to grade.

What was measured

packages/plugin-map/src/ObjectMap.tsx:588-592, the line immediately above the one #5976 fixed:

const rawDataConfig = getDataConfig(schema);
// Memoize dataConfig using deep comparison to prevent infinite loops
const dataConfig = useMemo(() => {
 return rawDataConfig;
}, [JSON.stringify(rawDataConfig)]);

getDataConfig(schema) is called bare in the render body — structurally the same shape as the #5976 defect. The difference is where the cost lands: dataConfig does end up with a stable identity, so this is not the same bug. It buys that stability by running JSON.stringify over the config on every render, plus a fresh getDataConfig call to feed it.

The reason that mattered is real: dataConfig is a dependency of the fetch effect, which calls setData — a fresh identity there is a re-render loop, not just waste. That is what the "prevent infinite loops" comment records.

Why the serialize now looks unnecessary rather than merely costly

#5976 established, by tracing all three callers, that the schema identity reaching this component is already stable across the renders that matter:

• SchemaRenderer hands over the memoized evaluatedSchema (SchemaRenderer.tsx:516);
• ElementDataSourceGate hands over mapped, a React.useMemo in useElementDataSourceSchema;
• ListView's case 'map' flatten hands over viewComponentSchema, a React.useMemo (ListView.tsx:2007);
• and every re-render ObjectMap causes itself leaves the prop untouched by construction.

getDataConfig is a pure function of schema and reads nothing else, so

const dataConfig = useMemo(() => getDataConfig(schema), [schema]);

appears to give the same stable identity the effect needs, with no serialize and no per-render rebuild. That is the shape #5976's fix landed for mapConfig, and its identity test now pins it.

What has NOT been measured, and would need to be before acting

• Whether the loop the comment guards against is still reachable. The comment predates the caller-side memoization above; it should be confirmed the effect stays quiet under the identity-keyed form rather than assumed. ObjectMap's marker useMemo never memoizes — getMapConfig runs unmemoized in the render body, so mapConfig has a fresh identity every render #5976's pin covers the marker pipeline, not the fetch effect.
• Whether JSON.stringify is currently masking a false-equal. It is key-order sensitive and drops undefined values, so two semantically different configs can produce the same key (stale — actually wrong, not merely wasteful). I did not find a reachable path: getDataConfig builds its objects with literal key order in every branch, and the one passthrough branch returns the author's own schema.data object, whose key order is fixed per object. Recorded as "not found", not as "cannot happen".

Scope note

Not folded into PR #6016. That PR's claim is narrow — mapConfig's identity — and it deliberately leaves :590 untouched and says so, because this is a different value with a different consumer (an effect, not a derived-value memo) and a genuine loop hazard in its history. Changing it needs its own measurement of that effect.

Unassigned; filed plainly for triage to grade.

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Generated by Claude Code

[claude]

Concentrated triage batch: finding → pm:queue + domain:ui, Task, S — ObjectMap pays JSON.stringify(rawDataConfig) on every render (plus a bare getDataConfig call in the render body) to buy an identity useMemo(() => getDataConfig(schema), [schema]) gives for free. Apply the memo shape, verify the fetch-effect identity contract with the existing tests; if schema identity is itself unstable at some call site (the reason stringify was reached for), measure and report that instead of keeping the stringify.

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Generated by Claude Code

[yinlianghui]

Claimed + dispatched — domain:ui @ objectui execution seat

PM session session_01CSoz9uGhaaSgiq3hshtN7L, branch claude/issue-6018-objectmap-dataconfig-memo.
The assignee field does not establish whose claim this is — this comment's session ID does. No earlier claim comment exists.

裁决 (binding)

ObjectMap pays JSON.stringify(rawDataConfig) on every render (plus a bare getDataConfig call in the render body) to buy an identity that useMemo(() => getDataConfig(schema), [schema]) gives for free. Apply the memo shape, and verify the fetch-effect identity contract against the existing tests.

⛔ Premise fork — the important half

If schema identity is itself unstable at some call site — which is the reason someone reached for stringify in the first place — ⛔ measure and report that instead of keeping the stringify. Do not "fix" it by leaving the stringify in place, and do not silently swap one identity hack for another. An unstable schema identity is a different and larger card.

So: before applying the memo, find out whether any caller passes a fresh schema object per render. If one does, that is a stop-and-report.

Traps

⚠️ A performance card's pin is the identity contract, not the timing. ⛔ Do not assert on render counts as a proxy for speed. The distinguishing assertion is that the fetch effect does NOT re-fire when the component re-renders with an unchanged schema, and DOES re-fire when schema changes — proven red before the fix on at least one of those directions.

⚠️ useMemo is not a semantic guarantee — React may discard the cache. If any behaviour depends on the memo holding rather than merely being faster, say so; the correct tool there is a ref or a stable key, not useMemo.

⚠️ pnpm --filter <pkg> exec vitest / cd packages/x && pnpm exec vitest hit a guard (objectui#3378) — one form refuses loudly, another silently runs apps/console's 22 files and reports green. Always run vitest from the repo root; sanity-check the file/test count.

⚠️ tsc resolves workspace deps through dist while vitest aliases to src/ — a type-check red can be unbuilt siblings, a real error, or both. Build the closure, then re-read.

Standing rules

Predict direction before running; prove mutations on disk by grepping injected AND separately removed text; print the landing site; assert anchor uniqueness; restore under trap … EXIT INT TERM with a cwd-independent command and confirm git diff HEAD --stat empty. Derive gates by enumerating each CI job's own step list. Changeset: let check-changeset-presence decide and quote its verdict line; ⛔ never major.

Collision bounds

packages/plugin-map is yours alone. ⛔ #5977 (ObjectMap.listViewMapConfigReach.test.tsx stale narration) is open in the same area and is not yours — do not fold it in; report any same-file overlap. Eight sibling agents are live elsewhere — ⛔ do not edit packages/plugin-form/**, packages/components/**, packages/plugin-list/**, packages/plugin-detail/**, packages/types/**, packages/core/**, packages/plugin-kanban/**, packages/app-shell/src/utils/**, examples/schema-catalog/**, apps/site/**.

⛔ Leave the PR draft — the PM lands it.

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Generated by Claude Code