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feat(minifier): compress (a = b) === null || a === undefined to (a = b) == null #8637

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Merged
graphite-app merged 1 commit into from
Jan 21, 2025
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feat(minifier): compress (a = b) === null || a === undefined to (a = b) == null #8637

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156 changes: 105 additions & 51 deletions crates/oxc_minifier/src/peephole/substitute_alternate_syntax.rs
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
use oxc_allocator::Vec;
use oxc_allocator::{CloneIn, Vec};
use oxc_ast::{ast::*, NONE};
use oxc_ecmascript::{
constant_evaluation::{ConstantEvaluation, ValueType},
Expand Down Expand Up @@ -331,6 +331,9 @@ impl<'a, 'b> PeepholeOptimizations {
/// `foo === null || foo === undefined` => `foo == null`
/// `foo !== null && foo !== undefined` => `foo != null`
///
/// Also supports `(a = foo.bar) === null || a === undefined` which commonly happens when
/// optional chaining is lowered. (`(a=foo.bar)==null`)
///
/// This compression assumes that `document.all` is a normal object.
/// If that assumption does not hold, this compression is not allowed.
/// - `document.all === null || document.all === undefined` is `false`
Expand All @@ -346,8 +349,8 @@ impl<'a, 'b> PeepholeOptimizations {
LogicalOperator::Coalesce => return None,
};
if let Some(new_expr) = Self::try_compress_is_null_or_undefined_for_left_and_right(
&expr.left,
&expr.right,
&mut expr.left,
&mut expr.right,
expr.span,
target_ops,
ctx,
Expand All @@ -360,10 +363,11 @@ impl<'a, 'b> PeepholeOptimizations {
if left.operator != op {
return None;
}
let new_span = Span::new(left.right.span().start, expr.span.end);
Self::try_compress_is_null_or_undefined_for_left_and_right(
&left.right,
&expr.right,
Span::new(left.right.span().start, expr.span.end),
&mut left.right,
&mut expr.right,
new_span,
target_ops,
ctx,
)
Expand All @@ -378,60 +382,93 @@ impl<'a, 'b> PeepholeOptimizations {
}

fn try_compress_is_null_or_undefined_for_left_and_right(
left: &Expression<'a>,
right: &Expression<'a>,
left: &mut Expression<'a>,
right: &mut Expression<'a>,
span: Span,
(find_op, replace_op): (BinaryOperator, BinaryOperator),
ctx: Ctx<'a, 'b>,
) -> Option<Expression<'a>> {
let pair = Self::commutative_pair(
(&left, &right),
|a| {
if let Expression::BinaryExpression(op) = a {
if op.operator == find_op {
return Self::commutative_pair(
(&op.left, &op.right),
|a_a| a_a.is_null().then_some(a_a.span()),
|a_b| {
if let Expression::Identifier(id) = a_b {
Some((a_b.span(), (*id).clone()))
} else {
None
}
},
);
enum LeftPairValueResult {
Null(Span),
Undefined,
}

let (
Expression::BinaryExpression(left_binary_expr),
Expression::BinaryExpression(right_binary_expr),
) = (left, right)
else {
return None;
};
if left_binary_expr.operator != find_op || right_binary_expr.operator != find_op {
return None;
}

let is_null_or_undefined = |a: &Expression| {
if a.is_null() {
Some(LeftPairValueResult::Null(a.span()))
} else if a.evaluate_to_undefined() {
Some(LeftPairValueResult::Undefined)
} else {
None
}
};
let is_id_or_assign_to_id = |b: &Expression| match b {
Expression::Identifier(id) => Some(id.name.clone_in(ctx.ast.allocator)),
Expression::AssignmentExpression(assign_expr) => {
if assign_expr.operator == AssignmentOperator::Assign {
if let AssignmentTarget::AssignmentTargetIdentifier(id) = &assign_expr.left {
return Some(id.name.clone_in(ctx.ast.allocator));
}
}
None
}
_ => None,
};
let (left_value, (left_non_value_expr, left_id_name)) = {
let left_value;
let left_non_value;
if let Some(v) = is_null_or_undefined(&left_binary_expr.left) {
left_value = v;
let left_non_value_id = is_id_or_assign_to_id(&left_binary_expr.right)?;
left_non_value = (&mut left_binary_expr.right, left_non_value_id);
} else {
left_value = is_null_or_undefined(&left_binary_expr.right)?;
let left_non_value_id = is_id_or_assign_to_id(&left_binary_expr.left)?;
left_non_value = (&mut left_binary_expr.left, left_non_value_id);
}
(left_value, left_non_value)
};

let (right_value, right_id) = Self::commutative_pair(
(&right_binary_expr.left, &right_binary_expr.right),
|a| match left_value {
LeftPairValueResult::Null(_) => a.evaluate_to_undefined().then_some(None),
LeftPairValueResult::Undefined => a.is_null().then_some(Some(a.span())),
},
|b| {
if let Expression::BinaryExpression(op) = b {
if op.operator == find_op {
return Self::commutative_pair(
(&op.left, &op.right),
|b_a| b_a.evaluate_to_undefined().then_some(()),
|b_b| {
if let Expression::Identifier(id) = b_b {
Some((*id).clone())
} else {
None
}
},
)
.map(|v| v.1);
}
if let Expression::Identifier(id) = b {
Some(id)
} else {
None
}
None
},
);
let ((null_expr_span, (left_id_expr_span, left_id_ref)), right_id_ref) = pair?;
if left_id_ref.name != right_id_ref.name {
)?;

if left_id_name != right_id.name {
return None;
}
let left_id_expr =
ctx.ast.expression_identifier_reference(left_id_expr_span, left_id_ref.name);
let null_expr = ctx.ast.expression_null_literal(null_expr_span);
Some(ctx.ast.expression_binary(span, left_id_expr, replace_op, null_expr))

let null_expr_span = match left_value {
LeftPairValueResult::Null(span) => span,
LeftPairValueResult::Undefined => right_value.unwrap(),
};
Some(ctx.ast.expression_binary(
span,
ctx.ast.move_expression(left_non_value_expr),
replace_op,
ctx.ast.expression_null_literal(null_expr_span),
))
}

/// Compress `a || (a = b)` to `a ||= b`
Expand Down Expand Up @@ -539,14 +576,14 @@ impl<'a, 'b> PeepholeOptimizations {
}
}

fn commutative_pair<A, F, G, RetF: 'a, RetG: 'a>(
pair: (&A, &A),
fn commutative_pair<'x, A, F, G, RetF: 'x, RetG: 'x>(
pair: (&'x A, &'x A),
check_a: F,
check_b: G,
) -> Option<(RetF, RetG)>
where
F: Fn(&A) -> Option<RetF>,
G: Fn(&A) -> Option<RetG>,
F: Fn(&'x A) -> Option<RetF>,
G: Fn(&'x A) -> Option<RetG>,
{
if let Some(a) = check_a(pair.0) {
if let Some(b) = check_b(pair.1) {
Expand All @@ -559,6 +596,7 @@ impl<'a, 'b> PeepholeOptimizations {
}
None
}

fn try_fold_loose_equals_undefined(
e: &mut BinaryExpression<'a>,
ctx: Ctx<'a, 'b>,
Expand Down Expand Up @@ -1782,6 +1820,22 @@ mod test {
test("foo !== 1 && foo !== null && foo !== void 0", "foo !== 1 && foo != null");
test("foo !== 1 || foo !== void 0 && foo !== null", "foo !== 1 || foo != null");
test_same("foo !== void 0 && bar !== null");

test("(_foo = foo) === null || _foo === undefined", "(_foo = foo) == null");
test("(_foo = foo) === null || _foo === void 0", "(_foo = foo) == null");
test("(_foo = foo.bar) === null || _foo === undefined", "(_foo = foo.bar) == null");
test("(_foo = foo) !== null && _foo !== undefined", "(_foo = foo) != null");
test("(_foo = foo) === undefined || _foo === null", "(_foo = foo) == null");
test("(_foo = foo) === void 0 || _foo === null", "(_foo = foo) == null");
test(
"(_foo = foo) === null || _foo === void 0 || _foo === 1",
"(_foo = foo) == null || _foo === 1",
);
test(
"_foo === 1 || (_foo = foo) === null || _foo === void 0",
"_foo === 1 || (_foo = foo) == null",
);
test_same("(_foo = foo) === void 0 || bar === null");
}

#[test]
Expand Down
4 changes: 2 additions & 2 deletions tasks/minsize/minsize.snap
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -21,7 +21,7 @@ Original | minified | minified | gzip | gzip | Fixture

3.20 MB | 1.01 MB | 1.01 MB | 332.00 kB | 331.56 kB | echarts.js

6.69 MB | 2.31 MB | 2.31 MB | 492.53 kB | 488.28 kB | antd.js
6.69 MB | 2.31 MB | 2.31 MB | 491.99 kB | 488.28 kB | antd.js

10.95 MB | 3.49 MB | 3.49 MB | 907.24 kB | 915.50 kB | typescript.js
10.95 MB | 3.48 MB | 3.49 MB | 905.39 kB | 915.50 kB | typescript.js

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