refactor in more idiomatic way without relying on undocumented behavior

pmndrs · Mar 27, 2021 · 130e2e1 · 130e2e1
1 parent 45e355f
commit 130e2e1
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Showing 2 changed files with 13 additions and 13 deletions.
diff --git a/.size-snapshot.json b/.size-snapshot.json
@@ -14,9 +14,9 @@
     }
   },
   "utils.module.js": {
-    "bundled": 8383,
-    "minified": 3692,
-    "gzipped": 1489,
+    "bundled": 8382,
+    "minified": 3699,
+    "gzipped": 1481,
     "treeshaked": {
       "rollup": {
         "code": 28,
@@ -103,9 +103,9 @@
     "gzipped": 3467
   },
   "utils.js": {
-    "bundled": 11566,
-    "minified": 5645,
-    "gzipped": 2105
+    "bundled": 11579,
+    "minified": 5650,
+    "gzipped": 2098
   },
   "devtools.js": {
     "bundled": 2394,

diff --git a/src/utils/atomWithDefault.ts b/src/utils/atomWithDefault.ts
@@ -4,23 +4,23 @@ import type { Read } from '../core/types'
 export function atomWithDefault<Value>(
   getDefault: Read<Value>
 ): PrimitiveAtom<Value> {
-  const overwrittenAtom = atom(false)
+  const EMPTY = Symbol()
+  const overwrittenAtom = atom<Value | typeof EMPTY>(EMPTY)
   const anAtom: PrimitiveAtom<Value> = atom(
     (get) => {
-      if (get(overwrittenAtom)) {
-        return get(anAtom)
+      const overwritten = get(overwrittenAtom)
+      if (overwritten !== EMPTY) {
+        return overwritten
       }
       return getDefault(get)
     },
-    (get, set, update) => {
-      set(overwrittenAtom, true)
+    (get, set, update) =>
       set(
-        anAtom,
+        overwrittenAtom,
         typeof update === 'function'
           ? (update as (prev: Value) => Value)(get(anAtom))
           : update
       )
-    }
   )
   return anAtom
 }