fix: readAtomState in write/get too (pmndrs#298)

* add failing test * fix: readAtomState in write/get too
edisonLzy · Feb 15, 2021 · 0701416 · 0701416
1 parent 82c9fdf
commit 0701416
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Showing 2 changed files with 47 additions and 11 deletions.
diff --git a/src/core/vanilla.ts b/src/core/vanilla.ts
@@ -407,34 +407,37 @@ const writeAtomState = <Value, Update>(
   try {
     const promiseOrVoid = atom.write(
       ((a: AnyAtom) => {
-        const aState = getAtomState(nextState, a)
-        if (!aState) {
-          if (hasInitialValue(a)) {
-            return a.init
-          }
+        // We pass dummy updateState and throw away nextState.
+        // There might be a better implementation.
+        const [aState] = readAtomState(nextState, () => {}, a)
+        if (aState.re) {
+          throw aState.re // read error
+        }
+        if (aState.rp) {
           if (
             typeof process === 'object' &&
             process.env.NODE_ENV !== 'production'
           ) {
             console.warn(
-              'Unable to read an atom without initial value in write function. Please useAtom in advance.',
+              'Reading pending atom state in write operation. We throw a promise for now.',
               a
             )
           }
-          throw new Error('uninitialized atom')
+          throw aState.rp // read promise
+        }
+        if ('v' in aState) {
+          return aState.v
         }
         if (
-          aState.rp &&
           typeof process === 'object' &&
           process.env.NODE_ENV !== 'production'
         ) {
-          // TODO will try to detect this
           console.warn(
-            'Reading pending atom state in write operation. We need to detect this and fallback. Please file an issue with repro.',
+            '[Bug] no value found while reading atom in write operation. This probably a bug.',
             a
           )
         }
-        return aState.v
+        throw new Error('no value found')
       }) as Getter,
       ((a: AnyWritableAtom, v: unknown) => {
         if (a === atom) {

diff --git a/tests/dependency.test.tsx b/tests/dependency.test.tsx
@@ -345,3 +345,36 @@ it('derived atom to update base atom in callback', async () => {
   fireEvent.click(getByText('button'))
   await findByText('commits: 2, count: 2, doubled: 4')
 })
+
+it('can read sync derived atom in write without initializing', async () => {
+  const countAtom = atom(1)
+  const doubledAtom = atom((get) => get(countAtom) * 2)
+  const addAtom = atom(null, (get, set, num: number) => {
+    set(countAtom, get(doubledAtom) / 2 + num)
+  })
+
+  const Counter: React.FC = () => {
+    const [count] = useAtom(countAtom)
+    const [, add] = useAtom(addAtom)
+    return (
+      <>
+        <div>count: {count}</div>
+        <button onClick={() => add(1)}>button</button>
+      </>
+    )
+  }
+
+  const { getByText, findByText } = render(
+    <Provider>
+      <Counter />
+    </Provider>
+  )
+
+  await findByText('count: 1')
+
+  fireEvent.click(getByText('button'))
+  await findByText('count: 2')
+
+  fireEvent.click(getByText('button'))
+  await findByText('count: 3')
+})