perf(electron-service): batch updateAllMocks into a single CDP round-trip

[goosewobbler]

Summary

• Closes perf(electron-service): batch updateAllMocks into a single CDP round-trip #268 — element-command overrides previously paid N CDP round-trips per click/setValue/etc (one per registered mock). The scheduler now performs at most one native (browser.electron.execute) and one browser-mode (browser.execute) round-trip per batch regardless of mock count.
• Each mock variant (api / prototype / constructor / browser-mode) exposes a JSON-serialisable __accessor and a local __applyCalls(data) method. The batched scheduler reads all mocks in one execute and dispatches slices to each mock's __applyCalls with no further I/O.
• Per-mock mock.update() is unchanged for explicit user calls and withImplementation.

Commit layout

1. feat(native-types) — adds ElectronMockReadAccessor plus the two new optional hooks on ElectronMockInstance (types only).
2. refactor(electron-service) — wires __accessor + __applyCalls onto every mock variant; behavior-preserving (update() now delegates its apply phase to the same helper).
3. perf(electron-service) — rewrites MockUpdateScheduler#runOnce to split by accessor kind and batch each subset; updates one existing scheduler test and adds three new ones.

Test plan

• pnpm --filter @wdio/electron-service test — 510 tests pass (was 507 before the refactor; 3 new + 1 updated).
• pnpm --filter @wdio/electron-service lint — clean (pre-existing warnings only).
• pnpm --filter @wdio/electron-service typecheck and pnpm exec turbo run typecheck — all 21 tasks pass.
• E2E acceptance: should trigger mock updates when DOM interactions occur in e2e/test/electron/mocking.spec.ts — needs a built app to run; please verify in CI.

New unit tests

• should batch updates for ≥2 mocks into a single browser.electron.execute call — covers all three native accessor kinds (api, prototype, constructor) and asserts exactly one CDP call.
• should batch updates for ≥2 browser-mode mocks into a single browser.execute call — registers two browser-mode mocks, asserts exactly one browser.execute call, and verifies the payload round-trips through parseCallData.
• should split native and browser-mode mocks across exactly two round-trips — proves the routing split fires both transports exactly once when both kinds are registered.

The existing concurrent-scheduler and recovery tests still pass via a small legacy fallback that calls mock.update() for any mock without an accessor — kept narrowly so plain test doubles ({ update: vi.fn() }) continue to work without restructuring.

Sibling work (follow-up)

The issue notes that @wdio/tauri-service has the same per-mock-update cost. Not included here; should be filed/folded as a follow-up once this pattern lands.

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[greptile-apps]

Greptile Summary

This PR replaces the per-mock update() call-per-element-command pattern with a batched scheduler that collapses all native mocks into a single browser.electron.execute round-trip and all browser-mode mocks into a single browser.execute round-trip, regardless of how many mocks are registered.

• Mock variants (api, prototype, constructor, browser) each expose a JSON-serialisable __accessor and a synchronous __applyCalls closure; the scheduler reads all state in one call and dispatches slices locally with no further I/O.
• Legacy compatibility is preserved via a narrow fallback that calls mock.update() for objects without an accessor, keeping existing test doubles working without restructuring.
• Four new unit tests verify the single-round-trip invariant for native and browser-mode batches, the mixed-transport split, and per-reader failure isolation.

Confidence Score: 5/5

Safe to merge — the batch path is well-tested with four new unit tests covering all transport variants and failure isolation, and the legacy fallback keeps existing doubles working without changes.

The refactor is behaviour-preserving: mock.update() delegates to the same applyCalls closure the scheduler uses, so per-mock and batched paths are always in sync. The one asymmetry found (missing ?? fallback before parseCallData in the browser-mode loop) is guarded at runtime because parseCallData already accepts null from the existing per-mock path.

packages/electron-service/src/service.ts — specifically the batchUpdateBrowserModeMocks post-execute loop, which lacks the explicit null-fallback that its native counterpart uses.

Important Files Changed

Filename	Overview
packages/electron-service/src/service.ts	Core scheduler rewrite: splits mocks into native/browser/legacy buckets and batches each in a single round-trip. Minor asymmetry — batchUpdateBrowserModeMocks lacks the ?? fallback that batchUpdateNativeMocks uses before calling parseCallData.
packages/electron-service/src/mock.ts	Extracts applyCalls closure shared by scheduler batch path and mock.update(); adds __accessor/__applyCalls to both the inner mock and the wrapper mock. Behaviour-preserving refactor.
packages/electron-service/src/classMock.ts	Extracts applyConstructorCalls/applyCalls closures for prototype and constructor mocks; both __accessor and __applyCalls are wired consistently alongside mock.update() delegation.
packages/electron-service/test/service.spec.ts	Adds four new scheduler tests covering native-batch, browser-mode batch, mixed-transport split, and per-reader failure isolation; updates the existing element-override test to use the new accessor pattern.
packages/native-types/src/electron.ts	Adds ElectronMockReadAccessor union type and optional __accessor/__applyCalls fields to ElectronMockInstance; clearly documented as service-internal.
packages/electron-service/src/mockFactory.ts	Exports MockApplyData interface and re-exports ElectronMockReadAccessor as MockReadAccessor alias for use across service modules. Pure type additions.
packages/native-types/src/index.ts	Adds ElectronMockReadAccessor to the public re-export list. Trivial barrel update.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[Element command triggered\nclick / setValue / etc.] --> B[MockUpdateScheduler#runOnce]
    B --> C{Classify each mock\nby __accessor.kind}
    C -->|kind = api/prototype/constructor| D[native bucket]
    C -->|kind = browser| E[browserMode bucket]
    C -->|no __accessor| F[legacy bucket]

    D --> G[batchUpdateNativeMocks\nbrowser.electron.execute — 1 CDP call]
    E --> H[batchUpdateBrowserModeMocks\nbrowser.execute — 1 renderer call]
    F --> I[per-mock m.update\none call per legacy mock]

    G --> J[Inner Electron script\ndiscriminates api/prototype/constructor\nreturns Record<mockId, slice>]
    J --> K[Outer loop: __applyCalls per mock\nno further I/O]

    H --> L[Inner browser script\nnew Function per channel read\nreturns Record<mockId, raw>]
    L --> M[parseCallData per slice\n__applyCalls per mock]

    G & H & I --> N[Promise.all resolves\nAll mocks synced]

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