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Merged
Boshen merged 1 commit into from
Jan 4, 2025
Merged

feat(minifier): improve minimizing conditionals #8238

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62 changes: 50 additions & 12 deletions crates/oxc_minifier/src/ast_passes/peephole_minimize_conditions.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -275,6 +275,9 @@ impl<'a> PeepholeMinimizeConditions {
Expression::BooleanLiteral(consequent_lit),
) = (&expr.left, &expr.right)
{
if !is_in_boolean_context(ctx) {
return None;
}
if consequent_lit.value {
return Some(ctx.ast.move_expression(&mut expr.left));
}
Expand Down Expand Up @@ -354,6 +357,8 @@ impl<'a> PeepholeMinimizeConditions {
}
}

let in_boolean_context = is_in_boolean_context(ctx);

// `a ? false : true` -> `!a`
// `a ? true : false` -> `!!a`
if let (
Expand All @@ -373,6 +378,10 @@ impl<'a> PeepholeMinimizeConditions {
}
(true, false) => {
let ident = ctx.ast.move_expression(&mut expr.test);

if in_boolean_context {
return Some(ident);
}
return Some(ctx.ast.expression_unary(
expr.span,
UnaryOperator::LogicalNot,
Expand All @@ -383,14 +392,6 @@ impl<'a> PeepholeMinimizeConditions {
}
}

let in_boolean_context = matches!(
ctx.parent(),
Ancestor::IfStatementTest(_)
| Ancestor::WhileStatementTest(_)
| Ancestor::DoWhileStatementTest(_)
| Ancestor::ExpressionStatementExpression(_)
);

// `x ? true : y` -> `x || y`
// `x ? false : y` -> `!x && y`
if let (Expression::Identifier(_), Expression::BooleanLiteral(consequent_lit), _) =
Expand Down Expand Up @@ -457,6 +458,39 @@ impl<'a> PeepholeMinimizeConditions {
}
}

// returns `true` if the current node is in a context in which the return
// value type is coerced to boolean.
// For example `if (condition)` and `return condition`
// inside the `if` stmt, `condition` is coerced to a boolean
// whereas inside the return, it is not
fn is_in_boolean_context(ctx: &mut TraverseCtx<'_>) -> bool {
for ancestor in ctx.ancestors() {
match ancestor {
Ancestor::IfStatementTest(_)
| Ancestor::WhileStatementTest(_)
| Ancestor::ForStatementTest(_)
| Ancestor::DoWhileStatementTest(_)
| Ancestor::ExpressionStatementExpression(_) => return true,
Ancestor::CallExpressionArguments(_)
| Ancestor::AssignmentPatternRight(_)
| Ancestor::BindingRestElementArgument(_)
| Ancestor::JSXSpreadAttributeArgument(_)
| Ancestor::NewExpressionArguments(_)
| Ancestor::ObjectPropertyKey(_)
| Ancestor::ObjectPropertyValue(_)
| Ancestor::ReturnStatementArgument(_)
| Ancestor::ThrowStatementArgument(_)
| Ancestor::YieldExpressionArgument(_)
| Ancestor::VariableDeclaratorInit(_) => return false,
_ => continue,
}
}
#[cfg(debug_assertions)]
unreachable!();
#[cfg(not(debug_assertions))]
false
}

/// <https://github.com/google/closure-compiler/blob/v20240609/test/com/google/javascript/jscomp/PeepholeMinimizeConditionsTest.java>
#[cfg(test)]
mod test {
Expand Down Expand Up @@ -754,11 +788,10 @@ mod test {

#[test]
fn test_minimize_expr_condition() {
fold("(x ? true : false) && y()", "!!x && y()");
fold("(x ? true : false) && y()", "x && y()");
fold("(x ? false : true) && y()", "!x && y()");
fold("(x ? true : y) && y()", "(!!x || y) && y()");
// TODO: drop the `!!`
fold("(x ? y : false) && y()", "(!!x && y) && y()");
fold("(x ? true : y) && y()", "(x || y) && y()");
fold("(x ? y : false) && y()", "(x && y) && y()");
fold("var x; (x && true) && y()", "var x; x && y()");
fold("var x; (x && false) && y()", "var x; false && y()");
fold("(x && true) && y()", "x && y()");
Expand All @@ -772,6 +805,11 @@ mod test {
fold("let x = foo ? true : false", "let x = !!foo");
fold("let x = foo ? true : bar", "let x = !!foo || bar");
fold("let x = foo ? bar : false", "let x = !!foo && bar");
fold("function x () { return a ? true : false }", "function x() { return !!a }");
fold("function x () { return a ? false : true }", "function x() { return !a }");
fold("function x () { return a ? true : b }", "function x() { return !!a || b }");
// can't be minified e.g. `a = ''` would return `''`
fold("function x() { return a && true }", "function x() { return a && true }");
}

#[test]
Expand Down
2 changes: 1 addition & 1 deletion tasks/minsize/minsize.snap
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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 | 331.90 kB | 331.56 kB | echarts.js

6.69 MB | 2.32 MB | 2.31 MB | 492.82 kB | 488.28 kB | antd.js
6.69 MB | 2.32 MB | 2.31 MB | 492.81 kB | 488.28 kB | antd.js

10.95 MB | 3.50 MB | 3.49 MB | 909.30 kB | 915.50 kB | typescript.js