feat(minifier): a != null ? a : b -> a ?? b (#8352)

crates/oxc_minifier/src/ast_passes/mod.rs

@@ -1,5 +1,6 @@
 use oxc_allocator::Vec;
 use oxc_ast::ast::*;
+use oxc_syntax::es_target::ESTarget;
 use oxc_traverse::{traverse_mut_with_ctx, ReusableTraverseCtx, Traverse, TraverseCtx};
 
 mod collapse_variable_declarations;
@@ -53,7 +54,7 @@ pub struct PeepholeOptimizations {
 impl PeepholeOptimizations {
     /// `in_fixed_loop`: Do not compress syntaxes that are hard to analyze inside the fixed loop.
     /// Opposite of `late` in Closure Compiler.
-    pub fn new(in_fixed_loop: bool, options: CompressOptions) -> Self {
+    pub fn new(target: ESTarget, in_fixed_loop: bool, options: CompressOptions) -> Self {
         Self {
             x0_statement_fusion: StatementFusion::new(),
             x1_minimize_exit_points: MinimizeExitPoints::new(),
@@ -61,7 +62,7 @@ impl PeepholeOptimizations {
             x3_collapse_variable_declarations: CollapseVariableDeclarations::new(),
             x4_peephole_fold_constants: PeepholeFoldConstants::new(),
             x5_peephole_remove_dead_code: PeepholeRemoveDeadCode::new(),
-            x6_peephole_minimize_conditions: PeepholeMinimizeConditions::new(),
+            x6_peephole_minimize_conditions: PeepholeMinimizeConditions::new(target),
             x7_peephole_replace_known_methods: PeepholeReplaceKnownMethods::new(),
             x8_convert_to_dotted_properties: ConvertToDottedProperties::new(in_fixed_loop),
             x9_peephole_substitute_alternate_syntax: PeepholeSubstituteAlternateSyntax::new(

crates/oxc_minifier/src/ast_passes/peephole_minimize_conditions.rs

@@ -2,6 +2,7 @@ use oxc_allocator::Vec;
 use oxc_ast::{ast::*, NONE};
 use oxc_ecmascript::constant_evaluation::ValueType;
 use oxc_span::{cmp::ContentEq, GetSpan, SPAN};
+use oxc_syntax::es_target::ESTarget;
 use oxc_traverse::{traverse_mut_with_ctx, Ancestor, ReusableTraverseCtx, Traverse, TraverseCtx};
 
 use crate::CompressorPass;
@@ -14,6 +15,7 @@ use crate::CompressorPass;
 ///
 /// <https://github.com/google/closure-compiler/blob/v20240609/src/com/google/javascript/jscomp/PeepholeMinimizeConditions.java>
 pub struct PeepholeMinimizeConditions {
+    target: ESTarget,
     pub(crate) changed: bool,
 }
 
@@ -56,7 +58,7 @@ impl<'a> Traverse<'a> for PeepholeMinimizeConditions {
             Expression::UnaryExpression(e) => Self::try_minimize_not(e, ctx),
             Expression::LogicalExpression(e) => Self::try_minimize_logical(e, ctx),
             Expression::BinaryExpression(e) => Self::try_minimize_binary(e, ctx),
-            Expression::ConditionalExpression(e) => Self::try_minimize_conditional(e, ctx),
+            Expression::ConditionalExpression(e) => self.try_minimize_conditional(e, ctx),
             _ => None,
         } {
             *expr = folded_expr;
@@ -66,8 +68,8 @@ impl<'a> Traverse<'a> for PeepholeMinimizeConditions {
 }
 
 impl<'a> PeepholeMinimizeConditions {
-    pub fn new() -> Self {
+    pub fn new(target: ESTarget) -> Self {
-        Self { changed: false }
+        Self { target, changed: false }
     }
 
     /// Try to minimize NOT nodes such as `!(x==y)`.
@@ -344,6 +346,7 @@ impl<'a> PeepholeMinimizeConditions {
 
     // based on https://github.com/evanw/esbuild/blob/df815ac27b84f8b34374c9182a93c94718f8a630/internal/js_ast/js_ast_helpers.go#L2745
     fn try_minimize_conditional(
+        &self,
         expr: &mut ConditionalExpression<'a>,
         ctx: &mut TraverseCtx<'a>,
     ) -> Option<Expression<'a>> {
@@ -633,7 +636,39 @@ impl<'a> PeepholeMinimizeConditions {
             }
         }
 
-        // TODO: Try using the "??" or "?." operators
+        // Try using the "??" or "?." operators
+        if let Expression::BinaryExpression(bin_expr) = &mut expr.test {
+            if bin_expr.operator == BinaryOperator::Equality
+                || bin_expr.operator == BinaryOperator::Inequality
+            {
+                if let Some(check) = {
+                    if bin_expr.left.is_null() {
+                        Some(&bin_expr.right)
+                    } else {
+                        Some(&bin_expr.left)
+                    }
+                } {
+                    // `a != null ? a : b` -> `a ?? b``
+                    if check.content_eq(if bin_expr.operator == BinaryOperator::Equality {
+                        &expr.alternate
+                    } else {
+                        &expr.consequent
+                    }) && self.target >= ESTarget::ES2020
+                    // TODO: this is probably a but too aggressive
+                        && matches!(check, Expression::Identifier(_))
+                    {
+                        return Some(ctx.ast.expression_logical(
+                            SPAN,
+                            ctx.ast.move_expression(&mut expr.consequent),
+                            LogicalOperator::Coalesce,
+                            ctx.ast.move_expression(&mut expr.alternate),
+                        ));
+                    }
+
+                    // TODO: `a != null ? a.b.c[d](e) : undefined` -> `a?.b.c[d](e)``
+                }
+            }
+        }
 
         // Non esbuild optimizations
 
@@ -812,12 +847,13 @@ impl<'a> PeepholeMinimizeConditions {
 #[cfg(test)]
 mod test {
     use oxc_allocator::Allocator;
+    use oxc_syntax::es_target::ESTarget;
 
     use crate::tester;
 
     fn test(source_text: &str, positive: &str) {
         let allocator = Allocator::default();
-        let mut pass = super::PeepholeMinimizeConditions::new();
+        let mut pass = super::PeepholeMinimizeConditions::new(ESTarget::ES2025);
         tester::test(&allocator, source_text, positive, &mut pass);
     }
 
@@ -2003,7 +2039,8 @@ mod test {
         test("var a; a ? b(c, d) : b(e, d)", "var a; b(a ? c : e, d)");
         test("var a; a ? b(...c) : b(...e)", "var a; b(...a ? c : e)");
         test("var a; a ? b(c) : b(e)", "var a; b(a ? c : e)");
-        // test("a != null ? a : b", "a ?? b");
+        test("a != null ? a : b", "a ?? b");
+        test_same("a() != null ? a() : b");
         // test("a != null ? a.b.c[d](e) : undefined", "a?.b.c[d](e)");
     }
 }

crates/oxc_minifier/src/compressor.rs

@@ -34,8 +34,10 @@ impl<'a> Compressor<'a> {
         RemoveSyntax::new(self.options).build(program, &mut ctx);
         // RemoveUnusedCode::new(self.options).build(program, &mut ctx);
         Normalize::new().build(program, &mut ctx);
-        PeepholeOptimizations::new(true, self.options).run_in_loop(program, &mut ctx);
+        PeepholeOptimizations::new(self.options.target, true, self.options)
-        PeepholeOptimizations::new(false, self.options).build(program, &mut ctx);
+            .run_in_loop(program, &mut ctx);
+        PeepholeOptimizations::new(self.options.target, false, self.options)
+            .build(program, &mut ctx);
     }
 
     pub fn dead_code_elimination(self, program: &mut Program<'a>) {

tasks/minsize/minsize.snap

@@ -3,25 +3,25 @@ Original   | minified   | minified   | gzip       | gzip       | Fixture
 -------------------------------------------------------------------------------------
 72.14 kB   | 23.70 kB   | 23.70 kB   | 8.61 kB    | 8.54 kB    | react.development.js
 
-173.90 kB  | 59.79 kB   | 59.82 kB   | 19.40 kB   | 19.33 kB   | moment.js 
+173.90 kB  | 59.77 kB   | 59.82 kB   | 19.39 kB   | 19.33 kB   | moment.js 
 
-287.63 kB  | 90.08 kB   | 90.07 kB   | 32.02 kB   | 31.95 kB   | jquery.js 
+287.63 kB  | 90.02 kB   | 90.07 kB   | 32.01 kB   | 31.95 kB   | jquery.js 
 
-342.15 kB  | 118.09 kB  | 118.14 kB  | 44.43 kB   | 44.37 kB   | vue.js    
+342.15 kB  | 118.08 kB  | 118.14 kB  | 44.43 kB   | 44.37 kB   | vue.js    
 
-544.10 kB  | 71.74 kB   | 72.48 kB   | 26.14 kB   | 26.20 kB   | lodash.js 
+544.10 kB  | 71.72 kB   | 72.48 kB   | 26.15 kB   | 26.20 kB   | lodash.js 
 
-555.77 kB  | 273.19 kB  | 270.13 kB  | 90.91 kB   | 90.80 kB   | d3.js     
+555.77 kB  | 272.89 kB  | 270.13 kB  | 90.85 kB   | 90.80 kB   | d3.js     
 
-1.01 MB    | 460.17 kB  | 458.89 kB  | 126.75 kB  | 126.71 kB  | bundle.min.js
+1.01 MB    | 460.13 kB  | 458.89 kB  | 126.74 kB  | 126.71 kB  | bundle.min.js
 
 1.25 MB    | 652.81 kB  | 646.76 kB  | 163.50 kB  | 163.73 kB  | three.js  
 
-2.14 MB    | 726.23 kB  | 724.14 kB  | 180.12 kB  | 181.07 kB  | victory.js
+2.14 MB    | 725.99 kB  | 724.14 kB  | 180.05 kB  | 181.07 kB  | victory.js
 
-3.20 MB    | 1.01 MB    | 1.01 MB    | 331.78 kB  | 331.56 kB  | echarts.js
+3.20 MB    | 1.01 MB    | 1.01 MB    | 331.68 kB  | 331.56 kB  | echarts.js
 
-6.69 MB    | 2.32 MB    | 2.31 MB    | 492.64 kB  | 488.28 kB  | antd.js   
+6.69 MB    | 2.32 MB    | 2.31 MB    | 492.60 kB  | 488.28 kB  | antd.js   
 
-10.95 MB   | 3.49 MB    | 3.49 MB    | 907.46 kB  | 915.50 kB  | typescript.js
+10.95 MB   | 3.49 MB    | 3.49 MB    | 907.25 kB  | 915.50 kB  | typescript.js