Fix object types not being shared across tabs

[Copilot]

When a store contains ref-wrapped objects (e.g., renderSettings = ref({ fps: 60 })), cross-tab updates via $patch were replacing the reactive object entirely instead of merging into it — breaking any component that held a direct reference to the old reactive object.

Root cause

The function form of $patch sets state[key] = newValue through Vue's reactive proxy, which triggers ref.value = newObject, creating a new reactive object. Components that captured the previous reactive reference (e.g. via storeToRefs or const settings = store.renderSettings) would hold a stale reference with no further updates.

Changes

• src/index.ts: Replace $patch(fn) with $patch(plainObject) built via reduce over keysToUpdate
• src/vanilla.ts: Replace store[key] = evt.newValue direct assignment with store.$patch({ [key]: evt.newValue })
• src/__tests__/plugin.test.ts: Added 14 vitest unit tests for the PiniaSharedState plugin
• src/__tests__/vanilla.test.ts: Added 9 vitest unit tests for the share() vanilla function

When $patch receives a plain object, Pinia internally calls mergeReactiveObjects(), which mutates existing reactive objects in-place rather than replacing them — preserving reactive references throughout.

// Before: replaces the reactive object reference
store.$patch((state) => {
  keysToUpdate.forEach((key) => {
    state[key] = newState.state[key]  // ref.value = newObject ← breaks captured refs
  })
})

// After: Pinia's mergeReactiveObjects mutates in-place
store.$patch(
  keysToUpdate.reduce((acc, key) => {
    acc[key] = newState.state[key]
    return acc
  }, {} as Partial<typeof store.$state>),
)

Testing

Unit tests cover:

• Primitive and object state sharing between tabs
• Reactive reference preservation — after a cross-tab update, store.settings === originalSettings (same object reference, mutated in-place)
• Partial merge without clobbering untouched keys
• omit, enable, and initialize options
• Two-tab simulation using two independent pinia instances
• sync() / unshare() lifecycle for the vanilla share() function
• Custom serializer support

broadcast-channel is mocked in-memory via vi.hoisted + vi.mock, so all tests run without browser APIs.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Object types cannot be shared</issue_title>
<issue_description>I tried to use pinia+PiniaSharedState as the main medium for communication between pages, and wrote the following code

import { defineStore } from 'pinia';

export const useSettingStore = defineStore(
""  "setting",""
  () => {
    const isAlwaysOnTop = ref(false);
    const renderSettings = ref({"
      fps: 60
    });
    const fps = ref(60);

    return {
      isAlwaysOnTop,
      renderSettings,
      fps
    };
  },
  {
    persist: true,
    share: {
      enable: true
    },
  }
);

fps can be shared, while renderSettings.fps cannot be shared. Is this by design? I think it should be a bug</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Object types cannot be shared #49

---

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[weiShaoY]

貌似项目没维护了

[wobsoriano]

@copilot use pnpm instead of npm

[Copilot]

@copilot use pnpm instead of npm

Switched to pnpm and removed the accidentally committed package-lock.json in df0050d.

[wobsoriano]

@copilot add a changeset

[Copilot]

@copilot add a changeset

Added a patch changeset in bff637f.

[wobsoriano]

@copilot can we add unit tests for this library? Use vitest

[Copilot]

@copilot can we add unit tests for this library? Use vitest

Added vitest unit tests in 5679070. There are 23 tests across two files:

• src/__tests__/plugin.test.ts (14 tests) — covers the PiniaSharedState plugin: primitive and object state sharing, the reactive-reference preservation fix, omit/enable/initialize options, two-tab simulation, and custom serializer
• src/__tests__/vanilla.test.ts (9 tests) — covers the share() function: primitive/object key sharing, timestamp deduplication, sync(), unshare(), and custom serializer

broadcast-channel is mocked with vi.hoisted + vi.mock so tests run entirely in-memory with no browser APIs needed.

[wobsoriano]

@copilot can we add unit tests for this library? Use vitest

Added vitest unit tests in 5679070. There are 23 tests across two files:

• src/__tests__/plugin.test.ts (14 tests) — covers the PiniaSharedState plugin: primitive and object state sharing, the reactive-reference preservation fix, omit/enable/initialize options, two-tab simulation, and custom serializer
• src/__tests__/vanilla.test.ts (9 tests) — covers the share() function: primitive/object key sharing, timestamp deduplication, sync(), unshare(), and custom serializer

broadcast-channel is mocked with vi.hoisted + vi.mock so tests run entirely in-memory with no browser APIs needed.

Great! Does it cover the issue that this PR is trying to fix as welll?

[Copilot]

@copilot can we add unit tests for this library? Use vitest

Added vitest unit tests in [5679070](5679070bf8505181e0...

Yes — the "object state sharing (bug fix)" describe block in both test files directly replicates the reported scenario (settings = ref({ fps: 60 }) updated cross-tab):

• applies nested object updates from another tab — verifies that store.settings.fps becomes 30 after a cross-tab message (the bug: this value would stay 60 before the fix)
• preserves the reactive object reference when merging updates — verifies store.settings === originalSettings after the update (the root cause: old code replaced the reactive object, breaking captured references)
• synchronises object state from tab1 to tab2 — end-to-end two-pinia simulation of the same scenario

The same pair of tests exists in vanilla.test.ts for the share() function.

[wobsoriano]

貌似项目没维护了

surprise!