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feat(minifier): fold typeof foo == undefined into foo == undefined when possible #8160

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merged 3 commits into from
Dec 29, 2024
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feat(minifier): fold typeof foo == undefined into foo == undefined when possible #8160

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f0c850c
feat(minifier): fold `typeof foo == undefined` into `foo == undefined…
sapphi-red Dec 28, 2024
7242612
[autofix.ci] apply automated fixes
autofix-ci[bot] Dec 28, 2024
479e426
chore: fix tests
sapphi-red Dec 28, 2024
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52 changes: 44 additions & 8 deletions crates/oxc_minifier/src/ast_passes/peephole_substitute_alternate_syntax.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -239,8 +239,10 @@ impl<'a, 'b> PeepholeSubstituteAlternateSyntax {
}
}

/// Compress `typeof foo == "undefined"` into `typeof foo > "u"`
/// Compress `typeof foo == "undefined"`
///
/// - `typeof foo == "undefined"` (if foo is resolved) -> `foo === undefined`
/// - `typeof foo != "undefined"` (if foo is resolved) -> `foo !== undefined`
/// - `typeof foo == "undefined"` -> `typeof foo > "u"`
/// - `typeof foo != "undefined"` -> `typeof foo < "u"`
///
Expand All @@ -249,12 +251,12 @@ impl<'a, 'b> PeepholeSubstituteAlternateSyntax {
expr: &mut BinaryExpression<'a>,
ctx: Ctx<'a, 'b>,
) -> Option<Expression<'a>> {
let new_op = match expr.operator {
let (new_eq_op, new_comp_op) = match expr.operator {
BinaryOperator::Equality | BinaryOperator::StrictEquality => {
BinaryOperator::GreaterThan
(BinaryOperator::StrictEquality, BinaryOperator::GreaterThan)
}
BinaryOperator::Inequality | BinaryOperator::StrictInequality => {
BinaryOperator::LessThan
(BinaryOperator::StrictInequality, BinaryOperator::LessThan)
}
_ => return None,
};
Expand All @@ -273,10 +275,17 @@ impl<'a, 'b> PeepholeSubstituteAlternateSyntax {
},
);
let (_void_exp, id_ref) = pair?;
let argument = Expression::Identifier(ctx.alloc(id_ref));
let left = ctx.ast.expression_unary(SPAN, UnaryOperator::Typeof, argument);
let right = ctx.ast.expression_string_literal(SPAN, "u", None);
Some(ctx.ast.expression_binary(expr.span, left, new_op, right))
let is_resolved = ctx.scopes().find_binding(ctx.current_scope_id(), &id_ref.name).is_some();
if is_resolved {
let left = Expression::Identifier(ctx.alloc(id_ref));
let right = ctx.ast.void_0(SPAN);
Some(ctx.ast.expression_binary(expr.span, left, new_eq_op, right))
} else {
let argument = Expression::Identifier(ctx.alloc(id_ref));
let left = ctx.ast.expression_unary(SPAN, UnaryOperator::Typeof, argument);
let right = ctx.ast.expression_string_literal(SPAN, "u", None);
Some(ctx.ast.expression_binary(expr.span, left, new_comp_op, right))
}
}

/// Compress `foo === null || foo === undefined` into `foo == null`.
Expand Down Expand Up @@ -1153,6 +1162,33 @@ mod test {
test_same("const foo = () => { foo; return 'baz' }");
}

#[test]
fn test_fold_is_typeof_equals_undefined_resolved() {
test("var x; typeof x !== 'undefined'", "var x; x !== void 0");
test("var x; typeof x != 'undefined'", "var x; x !== void 0");
test("var x; 'undefined' !== typeof x", "var x; x !== void 0");
test("var x; 'undefined' != typeof x", "var x; x !== void 0");

test("var x; typeof x === 'undefined'", "var x; x === void 0");
test("var x; typeof x == 'undefined'", "var x; x === void 0");
test("var x; 'undefined' === typeof x", "var x; x === void 0");
test("var x; 'undefined' == typeof x", "var x; x === void 0");

test(
"var x; function foo() { typeof x !== 'undefined' }",
"var x; function foo() { x !== void 0 }",
);
test(
"typeof x !== 'undefined'; function foo() { var x }",
"typeof x < 'u'; function foo() { var x }",
);
test("typeof x !== 'undefined'; { var x }", "x !== void 0; { var x }");
test("typeof x !== 'undefined'; { let x }", "typeof x < 'u'; { let x }");
test("typeof x !== 'undefined'; var x", "x !== void 0; var x");
// input and output both errors with same TDZ error
test("typeof x !== 'undefined'; let x", "x !== void 0; let x");
}

/// Port from <https://github.com/evanw/esbuild/blob/v0.24.2/internal/js_parser/js_parser_test.go#L4658>
#[test]
fn test_fold_is_typeof_equals_undefined() {
Expand Down
8 changes: 4 additions & 4 deletions tasks/minsize/minsize.snap
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Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,7 @@ Original | minified | minified | gzip | gzip | Fixture

173.90 kB | 60.16 kB | 59.82 kB | 19.49 kB | 19.33 kB | moment.js

287.63 kB | 90.59 kB | 90.07 kB | 32.19 kB | 31.95 kB | jquery.js
287.63 kB | 90.59 kB | 90.07 kB | 32.18 kB | 31.95 kB | jquery.js

342.15 kB | 118.61 kB | 118.14 kB | 44.54 kB | 44.37 kB | vue.js

Expand All @@ -17,11 +17,11 @@ Original | minified | minified | gzip | gzip | Fixture

1.25 MB | 656.66 kB | 646.76 kB | 164.14 kB | 163.73 kB | three.js

2.14 MB | 735.28 kB | 724.14 kB | 180.98 kB | 181.07 kB | victory.js
2.14 MB | 735.26 kB | 724.14 kB | 180.97 kB | 181.07 kB | victory.js

3.20 MB | 1.01 MB | 1.01 MB | 332.23 kB | 331.56 kB | echarts.js

6.69 MB | 2.36 MB | 2.31 MB | 494.93 kB | 488.28 kB | antd.js
6.69 MB | 2.36 MB | 2.31 MB | 494.89 kB | 488.28 kB | antd.js

10.95 MB | 3.51 MB | 3.49 MB | 910.92 kB | 915.50 kB | typescript.js
10.95 MB | 3.51 MB | 3.49 MB | 910.90 kB | 915.50 kB | typescript.js

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