fix(atoms): replace top-level array state directly in signal.mutate

packages/atoms/src/classes/Signal.ts

@@ -80,13 +80,11 @@ export const doMutate = <G extends NodeGenerics>(
 
     const transactions: Transaction[] = []
 
-    if (isMutatable(newState)) {
+    if (Array.isArray(newState)) {
+      transactions.push({ k: [], v: newState })
+    } else if (isMutatable(newState)) {
       const empty = (
-        newState instanceof Set
-          ? new Set()
-          : Array.isArray(newState)
-            ? []
-            : {}
+        newState instanceof Set ? new Set() : {}
       ) as G['State']
 
       recursivelyMutate(
@@ -138,7 +136,10 @@ export const doMutate = <G extends NodeGenerics>(
     // applied as mutations; non-mutatable values (primitives, class instances,
     // etc.) are set as the entire new state.
     if (!transactions.length && result !== undefined) {
-      if (isMutatable(result)) {
+      if (Array.isArray(result)) {
+        newState = result
+        transactions.push({ k: [], v: result })
+      } else if (isMutatable(result)) {
         recursivelyMutate(proxyWrapper.p, result)
       } else {
         node.set(result as Settable<G['State']>, {
@@ -149,6 +150,9 @@ export const doMutate = <G extends NodeGenerics>(
         return
       }
     }
+  } else if (Array.isArray(mutatable)) {
+    newState = mutatable as G['State']
+    transactions.push({ k: [], v: mutatable })
   } else {
     recursivelyMutate(proxyWrapper.p, mutatable)
   }

packages/react/test/integrations/__snapshots__/proxies.test.tsx.snap

@@ -5,13 +5,14 @@ exports[`proxies array operations 1`] = `
   [
     [
       {
-        "k": [
-          "0",
-          "a",
-        ],
+        "k": [],
         "v": [
-          11,
-          33,
+          {
+            "a": [
+              11,
+              33,
+            ],
+          },
         ],
       },
     ],

packages/react/test/integrations/proxies.test.tsx

@@ -1,4 +1,11 @@
-import { api, As, atom, injectSignal, Transaction } from '@zedux/atoms'
+import {
+  api,
+  As,
+  atom,
+  injectMappedSignal,
+  injectSignal,
+  Transaction,
+} from '@zedux/atoms'
 import { ecosystem } from '../utils/ecosystem'
 
 describe('proxies', () => {
@@ -317,7 +324,21 @@ describe('proxies', () => {
       state[3] = 40
     })
 
-    expect(signal.get()).toEqual([2, 3, 30, 40, 5])
+    expect(signal.get()).toEqual([2, 3, 30, 40])
+  })
+
+  test('function-form returning an array generates a single transaction', () => {
+    const calls: any[] = []
+    const signal = ecosystem.signal([1, 2, 3])
+
+    signal.on('mutate', transactions => {
+      calls.push(transactions)
+    })
+
+    signal.mutate(draft => [draft[0] + 10, draft[1] + 10])
+
+    expect(signal.get()).toEqual([11, 12])
+    expect(calls).toEqual([[{ k: [], v: [11, 12] }]])
   })
 
   describe('recursivelyMutate optimizations', () => {
@@ -382,6 +403,44 @@ describe('proxies', () => {
       expect(signal.get()).toEqual({ arr: [11, 21] })
       expect(calls).toEqual([[{ k: 'arr', v: [11, 21] }]])
     })
+
+    test('top-level array replaces instead of deep merging', () => {
+      const calls: any[] = []
+      const signal = ecosystem.signal([{ a: 1, b: 2 }, { c: 3 }])
+
+      signal.on('mutate', transactions => {
+        calls.push(transactions)
+      })
+
+      signal.mutate([{ a: 5 }])
+
+      // should replace entire array, not deep merge { a: 5 } into { a: 1, b: 2 }
+      expect(signal.get()).toEqual([{ a: 5 }])
+      expect(calls).toEqual([[{ k: [], v: [{ a: 5 }] }]])
+    })
+  })
+
+  test('mapped signal prefixes array replacement transaction with inner key', () => {
+    const testAtom = atom('mappedArr', () => {
+      const arrSignal = injectSignal([1, 2, 3])
+      const signal = injectMappedSignal({ arr: arrSignal })
+
+      return api(signal).setExports({ arrSignal })
+    })
+
+    const node = ecosystem.getNode(testAtom)
+    const calls: any[] = []
+
+    node.on('mutate', transactions => {
+      calls.push(transactions)
+    })
+
+    node.exports.arrSignal.mutate([10, 20])
+
+    expect(node.get()).toEqual({ arr: [10, 20] })
+    expect(calls).toEqual([[{ k: ['arr'], v: [10, 20] }]])
+
+    ecosystem.dehydrate({ exclude: [testAtom] })
   })
 
   describe('non-plain object handling', () => {

packages/react/test/integrations/signals.test.tsx

@@ -528,7 +528,7 @@ describe('signals', () => {
       ])
     })
 
-    test('mutate generates add transactions for each element of an array', () => {
+    test('mutate replaces array state directly with a single transaction', () => {
       const signal = ecosystem.signal<string[] | null>(null)
       let transactions: Transaction[] | undefined
 
@@ -538,10 +538,8 @@ describe('signals', () => {
 
       signal.mutate(['a', 'b'])
 
-      expect(transactions).toEqual([
-        { k: '0', v: 'a' },
-        { k: '1', v: 'b' },
-      ])
+      expect(transactions).toEqual([{ k: [], v: ['a', 'b'] }])
+      expect(signal.get()).toEqual(['a', 'b'])
     })
 
     test('mutate generates add transactions for each item in a set', () => {