1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
|
import { createElement, render } from 'preact';
import { setupScratch, teardown } from '../../../test/_util/helpers';
import { useMemo } from 'preact/hooks';
/** @jsx createElement */
describe('useMemo', () => {
/** @type {HTMLDivElement} */
let scratch;
beforeEach(() => {
scratch = setupScratch();
});
afterEach(() => {
teardown(scratch);
});
it('only recomputes the result when inputs change', () => {
let memoFunction = sinon.spy((a, b) => a + b);
const results = [];
function Comp({ a, b }) {
const result = useMemo(() => memoFunction(a, b), [a, b]);
results.push(result);
return null;
}
render(<Comp a={1} b={1} />, scratch);
render(<Comp a={1} b={1} />, scratch);
expect(results).to.deep.equal([2, 2]);
expect(memoFunction).to.have.been.calledOnce;
render(<Comp a={1} b={2} />, scratch);
render(<Comp a={1} b={2} />, scratch);
expect(results).to.deep.equal([2, 2, 3, 3]);
expect(memoFunction).to.have.been.calledTwice;
});
it('should rerun when deps length changes', () => {
let memoFunction = sinon.spy(() => 1 + 2);
function Comp({ all }) {
const deps = [1, all && 2].filter(Boolean);
const result = useMemo(() => memoFunction(), deps);
return result;
}
render(<Comp all />, scratch);
expect(memoFunction).to.have.been.calledOnce;
render(<Comp all={false} />, scratch);
expect(memoFunction).to.have.been.calledTwice;
});
it('should rerun when first run threw an error', () => {
let hasThrown = false;
let memoFunction = sinon.spy(() => {
if (!hasThrown) {
hasThrown = true;
throw new Error('test');
} else {
return 3;
}
});
function Comp() {
const result = useMemo(() => memoFunction(), []);
return result;
}
expect(() => render(<Comp />, scratch)).to.throw('test');
expect(memoFunction).to.have.been.calledOnce;
expect(() => render(<Comp />, scratch)).not.to.throw();
expect(memoFunction).to.have.been.calledTwice;
});
it('short circuits diffing for memoized components', () => {
let spy = sinon.spy();
let spy2 = sinon.spy();
const X = ({ count }) => {
spy();
return <span>{count}</span>;
};
const Y = ({ count }) => {
spy2();
return <p>{count}</p>;
};
const App = ({ x }) => {
const y = useMemo(() => <Y count={x} />, [x]);
return (
<div>
<X count={x} />
{y}
</div>
);
};
render(<App x={0} />, scratch);
expect(spy).to.be.calledOnce;
expect(spy2).to.be.calledOnce;
expect(scratch.innerHTML).to.equal('<div><span>0</span><p>0</p></div>');
render(<App x={0} />, scratch);
expect(spy).to.be.calledTwice;
expect(spy2).to.be.calledOnce;
expect(scratch.innerHTML).to.equal('<div><span>0</span><p>0</p></div>');
render(<App x={1} />, scratch);
expect(spy).to.be.calledThrice;
expect(spy2).to.be.calledTwice;
expect(scratch.innerHTML).to.equal('<div><span>1</span><p>1</p></div>');
render(<App x={1} />, scratch);
expect(spy2).to.be.calledTwice;
expect(scratch.innerHTML).to.equal('<div><span>1</span><p>1</p></div>');
render(<App x={2} />, scratch);
expect(spy2).to.be.calledThrice;
expect(scratch.innerHTML).to.equal('<div><span>2</span><p>2</p></div>');
});
});
|
