From 7719cba59606a9a01f1ab581bcf6ed690eeef0fa Mon Sep 17 00:00:00 2001
From: Michael <michaelzanggl@gmail.com>
Date: Sun, 5 Jan 2020 15:01:42 +0900
Subject: [PATCH] make isEmpty an accessor so it reacts to value mutations

---
 src/index.ts            |  8 ++++----
 test/promistate.spec.js | 12 ++++++++++--
 2 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/src/index.ts b/src/index.ts
index 311fd7f..986cb7a 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -22,13 +22,15 @@ function promistate<T>(action: (...args: CallbackArgs) => Promise<T>, options: P
     return {
         value: defaultValue,
         isPending: false,
-        isEmpty: isEmpty<T>(defaultValue),
         error: null,
 
+        get isEmpty() {
+            return this.isPending ? false : isEmpty(this.value)
+        },
+
         reset() {
             this.value = defaultValue
             this.isPending = false
-            this.isEmpty = isEmpty<T>(defaultValue)
             this.error = null
         },
 
@@ -38,12 +40,10 @@ function promistate<T>(action: (...args: CallbackArgs) => Promise<T>, options: P
             }
 
             this.isPending = true
-            this.isEmpty = false
             this.error = null
 
             return action.apply(this, args)
                 .then((result: T) => {
-                    this.isEmpty = isEmpty<T>(result)
                     this.value = result
                     this.isPending = false
                     return Status.RESOLVED
diff --git a/test/promistate.spec.js b/test/promistate.spec.js
index fc1b7f7..f5cfbe9 100644
--- a/test/promistate.spec.js
+++ b/test/promistate.spec.js
@@ -83,7 +83,7 @@ test('catches errors', async (assert) => {
 
     assert.equal(state.error.message, 'blub')
     assert.isFalse(state.isPending)
-    assert.isFalse(state.isEmpty)
+    assert.isTrue(state.isEmpty)
     assert.isNull(state.value)
     assert.equal(status, Status.ERROR)
 })
@@ -117,7 +117,7 @@ test('does throw error when option is set to let it bubble up', async (assert) =
 
     assert.equal(state.error.message, 'blub')
     assert.isFalse(state.isPending)
-    assert.isFalse(state.isEmpty)
+    assert.isTrue(state.isEmpty)
     assert.isNull(state.value)
 })
 
@@ -163,3 +163,11 @@ test('can access state in load function', async (assert) => {
 
     assert.equal(state.value, 2)
 })
+
+test('isEmpty reacts to value changes', async (assert) => {
+    const state = promistate(() => [], { defaultValue: [1] })
+    assert.isFalse(state.isEmpty)
+
+    state.value = []
+    assert.isTrue(state.isEmpty)
+})