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feat(minifier): for (;;) { var x } -> for (;;) var x; #8847

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Merged
graphite-app merged 1 commit into from
Feb 3, 2025
Merged

feat(minifier): for (;;) { var x } -> for (;;) var x; #8847

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5 changes: 4 additions & 1 deletion crates/oxc_minifier/src/peephole/collapse_variable_declarations.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -47,7 +47,10 @@ mod test {
#[test]
fn test_aggressive_redeclaration_in_for() {
test_same("for(var x = 1; x = 2; x = 3) x = 4");
test_same("for(var x = 1; y = 2; z = 3) {var a = 4}");
test(
"for(var x = 1; y = 2; z = 3) {var a = 4}",
"for(var x = 1; y = 2; z = 3) var a = 4",
);
test_same("var x; for(x = 1; x = 2; z = 3) x = 4");
}

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4 changes: 2 additions & 2 deletions crates/oxc_minifier/src/peephole/minimize_conditions.rs
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Expand Up @@ -1545,8 +1545,8 @@ mod test {
test("if (x) ;else { foo }", "x || foo");
test("if (x) {;} else { foo }", "x || foo");

test("if (x) { var foo } else { bar }", "if (x) { var foo } else bar");
test_same("if (x) foo; else { var bar }");
test("if (x) { var foo } else { bar }", "if (x) var foo; else bar");
test("if (x) foo; else { var bar }", "if (x) foo; else var bar");
}

#[test]
Expand Down
52 changes: 30 additions & 22 deletions crates/oxc_minifier/src/peephole/remove_dead_code.rs
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Expand Up @@ -127,26 +127,34 @@ impl<'a, 'b> PeepholeOptimizations {
stmt: &mut BlockStatement<'a>,
ctx: Ctx<'a, 'b>,
) -> Option<Statement<'a>> {
// Avoid compressing `if (x) { var x = 1 }` to `if (x) var x = 1` due to different
// semantics according to AnnexB, which lead to different semantics.
if stmt.body.len() == 1 && !stmt.body[0].is_declaration() {
return Some(stmt.body.remove(0));
}
if stmt.body.len() == 0 {
let parent = ctx.parent();
if parent.is_while_statement()
|| parent.is_do_while_statement()
|| parent.is_for_statement()
|| parent.is_for_in_statement()
|| parent.is_for_of_statement()
|| parent.is_block_statement()
|| parent.is_program()
{
// Remove the block if it is empty and the parent is a block statement.
return Some(ctx.ast.statement_empty(stmt.span));
match stmt.body.len() {
0 => {
let parent = ctx.parent();
if parent.is_while_statement()
|| parent.is_do_while_statement()
|| parent.is_for_statement()
|| parent.is_for_in_statement()
|| parent.is_for_of_statement()
|| parent.is_block_statement()
|| parent.is_program()
{
// Remove the block if it is empty and the parent is a block statement.
return Some(ctx.ast.statement_empty(stmt.span));
}
None
}
1 => {
let s = &stmt.body[0];
if matches!(s, Statement::VariableDeclaration(decl) if !decl.kind.is_var())
|| matches!(s, Statement::ClassDeclaration(_))
|| matches!(s, Statement::FunctionDeclaration(_))
{
return None;
}
Some(stmt.body.remove(0))
}
_ => None,
}
None
}

fn try_fold_if(
Expand Down Expand Up @@ -664,8 +672,8 @@ mod test {
test("a: { break a; console.log('unreachable'); }", "");
test("a: { break a; var x = 1; } x = 2;", "var x; x = 2;");

test_same("b: { var x = 1; } x = 2;");
test_same("a: b: { var x = 1; } x = 2;");
test("b: { var x = 1; } x = 2;", "b: var x = 1; x = 2;");
test("a: b: { var x = 1; } x = 2;", "a: b: var x = 1; x = 2;");
test("foo:;", "");
}

Expand Down Expand Up @@ -784,8 +792,8 @@ mod test {
test("try {} catch (e) { foo() } finally {}", "");
test("try {} finally { foo() }", "foo()");
test("try {} catch (e) { foo() } finally { bar() }", "bar()");
test("try {} finally { var x = foo() }", "{ var x = foo() }");
test("try {} catch (e) { foo() } finally { var x = bar() }", "{ var x = bar() }");
test("try {} finally { var x = foo() }", "var x = foo()");
test("try {} catch (e) { foo() } finally { var x = bar() }", "var x = bar()");
test("try {} finally { let x = foo() }", "{ let x = foo() }");
test("try {} catch (e) { foo() } finally { let x = bar() }", "{ let x = bar();}");
test("try {} catch (e) { } finally {}", "");
Expand Down
2 changes: 1 addition & 1 deletion crates/oxc_minifier/src/peephole/substitute_alternate_syntax.rs
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Expand Up @@ -1418,7 +1418,7 @@ mod 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'; { 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
Expand Down
6 changes: 3 additions & 3 deletions crates/oxc_minifier/tests/peephole/esbuild.rs
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Expand Up @@ -256,7 +256,7 @@ fn js_parser_test() {
test("x?.['y']()", "x?.y();");
test("x?.['y z']()", "x?.['y z']();");
test("x['y' + 'z']", "x.yz;");
// test("x?.['y' + 'z']", "x?.['yz'];");
test("x?.['y' + 'z']", "x?.yz;");
test("x['0']", "x[0];");
test("x['123']", "x[123];");
test("x['-123']", "x[-123];");
Expand All @@ -267,12 +267,12 @@ fn js_parser_test() {
test("x['-0x1']", "x['-0x1'];");
test("x['2147483647']", "x[2147483647];");
test("x['2147483648']", "x['2147483648'];");
// test("x['-2147483648']", "x[-2147483648];");
test("x['-2147483648']", "x[-2147483648];");
test("x['-2147483649']", "x['-2147483649'];");
test("while(1) { while (1) {} }", "for (;;) for (;;) ;");
test("while(1) { const x = y; }", "for (;;) { let x = y;}");
test("while(1) { let x; }", "for (;;) { let x;}");
// test("while(1) { var x; }", "for (;;) var x;");
test("while(1) { var x; }", "for (;;) var x;");
test("while(1) { class X {} }", "for (;;) { class X { }}");
// test("while(1) { function x() {} }", "for (;;) var x = function() { };");
test("while(1) { function* x() {} }", "for (;;) { function* x() { }}");
Expand Down
6 changes: 3 additions & 3 deletions tasks/minsize/minsize.snap
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Expand Up @@ -9,15 +9,15 @@ Original | minified | minified | gzip | gzip | Fixture

342.15 kB | 117.67 kB | 118.14 kB | 43.48 kB | 44.37 kB | vue.js

544.10 kB | 71.42 kB | 72.48 kB | 25.86 kB | 26.20 kB | lodash.js
544.10 kB | 71.40 kB | 72.48 kB | 25.86 kB | 26.20 kB | lodash.js

555.77 kB | 271.24 kB | 270.13 kB | 88.34 kB | 90.80 kB | d3.js
555.77 kB | 271.24 kB | 270.13 kB | 88.33 kB | 90.80 kB | d3.js

1.01 MB | 440.93 kB | 458.89 kB | 122.53 kB | 126.71 kB | bundle.min.js

1.25 MB | 650.33 kB | 646.76 kB | 160.96 kB | 163.73 kB | three.js

2.14 MB | 717.08 kB | 724.14 kB | 162.06 kB | 181.07 kB | victory.js
2.14 MB | 717.07 kB | 724.14 kB | 162.06 kB | 181.07 kB | victory.js

3.20 MB | 1.01 MB | 1.01 MB | 324.41 kB | 331.56 kB | echarts.js

Expand Down
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