Minify property accesses on object literals #1179

evanw · 2021-04-23T00:06:15Z

The code {a: {b: 1}}.a.b will now be minified to 1. This optimization is relatively complex and hard to do safely. Here are some tricky cases that are correctly handled:

var obj = {a: 1}
assert({a: 1, a: 2}.a === 2)
assert({a: 1, [String.fromCharCode(97)]: 2}.a === 2)
assert({__proto__: obj}.a === 1)
assert({__proto__: null}.a === undefined)
assert({__proto__: null}.__proto__ === undefined)
assert({a: function() { return this.b }, b: 1}.a() === 1)
assert(({a: 1}.a = 2) === 2)
assert(++{a: 1}.a === 2)
assert.throws(() => { new ({ a() {} }.a) })

Fixes #1166

lukeed · 2021-04-23T00:17:34Z

internal/js_parser/js_parser_test.go

@@ -2930,6 +2930,18 @@ func TestMangleObject(t *testing.T) {
 	expectPrintedMangle(t, "x = {a, ...'123', b}", "x = {a, ...\"123\", b};\n")
 	expectPrintedMangle(t, "x = {a, ...[1, 2, 3], b}", "x = {a, ...[1, 2, 3], b};\n")
 	expectPrintedMangle(t, "x = {a, ...(()=>{})(), b}", "x = {a, ...(() => {\n})(), b};\n")
+
+	// Check simple cases of object simplification (advanced cases are checked in end-to-end tests)
+	expectPrintedMangle(t, "x = {['y']: z}.y", "x = {y: z}.y;\n")


These, by themselves, are amazing! 🙌

simplify object literal property access

43d48f2

evanw merged commit 4109a81 into master Apr 23, 2021

evanw deleted the issues/1166 branch April 23, 2021 00:12

lukeed reviewed Apr 23, 2021

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Minify property accesses on object literals #1179

Minify property accesses on object literals #1179

evanw commented Apr 23, 2021

lukeed Apr 23, 2021

Minify property accesses on object literals #1179

Minify property accesses on object literals #1179

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evanw commented Apr 23, 2021

lukeed Apr 23, 2021

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