feat(minifier): improve folding block stmts (#6793)

oxc-project · Oct 23, 2024 · b4bc300 · b4bc300
1 parent 7c51b2f
commit b4bc300
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Showing 2 changed files with 64 additions and 12 deletions.
diff --git a/crates/oxc_minifier/src/ast_passes/peephole_remove_dead_code.rs b/crates/oxc_minifier/src/ast_passes/peephole_remove_dead_code.rs
@@ -146,7 +146,12 @@ impl<'a, 'b> PeepholeRemoveDeadCode {
                 return;
             }
             if block.body.len() == 0
-                && (ctx.parent().is_block_statement() || ctx.parent().is_program())
+                && (ctx.parent().is_while_statement()
+                    || ctx.parent().is_for_statement()
+                    || ctx.parent().is_for_in_statement()
+                    || ctx.parent().is_for_of_statement()
+                    || ctx.parent().is_block_statement()
+                    || ctx.parent().is_program())
             {
                 // Remove the block if it is empty and the parent is a block statement.
                 *stmt = ctx.ast.statement_empty(SPAN);
@@ -282,6 +287,53 @@ impl<'a, 'b> PeepholeRemoveDeadCode {
                 Expression::ObjectExpression(object_expr) => {
                     Self::try_fold_object_expression(object_expr, ctx)
                 }
+                Expression::TemplateLiteral(template_lit) => {
+                    template_lit.expressions.retain(
+                        oxc_ecmascript::side_effects::MayHaveSideEffects::may_have_side_effects,
+                    );
+
+                    let mut expressions = ctx.ast.move_vec(&mut template_lit.expressions);
+
+                    if expressions.len() == 0 {
+                        return Some(ctx.ast.statement_empty(SPAN));
+                    } else if expressions.len() == 1 {
+                        return Some(
+                            ctx.ast.statement_expression(
+                                template_lit.span,
+                                expressions.pop().unwrap(),
+                            ),
+                        );
+                    }
+
+                    return Some(ctx.ast.statement_expression(
+                        template_lit.span,
+                        ctx.ast.expression_from_sequence(
+                            ctx.ast.sequence_expression(template_lit.span, expressions),
+                        ),
+                    ));
+                }
+                Expression::BinaryExpression(bin_expr) => {
+                    let left = bin_expr.left.may_have_side_effects();
+                    let right = bin_expr.left.may_have_side_effects();
+
+                    if left && right {
+                        return None;
+                    }
+                    if !left && !right {
+                        return Some(ctx.ast.statement_empty(SPAN));
+                    }
+                    return Some(ctx.ast.statement_expression(
+                        bin_expr.span,
+                        ctx.ast.move_expression(if left {
+                            &mut bin_expr.right
+                        } else {
+                            &mut bin_expr.left
+                        }),
+                    ));
+                }
+                Expression::FunctionExpression(function_expr) if function_expr.id.is_none() => {
+                    Some(ctx.ast.statement_empty(SPAN))
+                }
                 _ => None,
             })
     }
@@ -503,22 +555,22 @@ mod test {
         fold("{if(false)if(false)if(false)foo(); {bar()}}", "bar()");
 
         fold("{'hi'}", "");
-        // fold("{x==3}", "");
-        // fold("{`hello ${foo}`}", "");
-        // fold("{ (function(){x++}) }", "");
-        // fold_same("function f(){return;}");
-        // fold("function f(){return 3;}", "function f(){return 3}");
+        fold("{x==3}", "");
+        fold("{`hello ${foo}`}", "");
+        fold("{ (function(){x++}) }", "");
+        fold_same("function f(){return;}");
+        fold("function f(){return 3;}", "function f(){return 3}");
         // fold_same("function f(){if(x)return; x=3; return; }");
         // fold("{x=3;;;y=2;;;}", "x=3;y=2");
 
         // Cases to test for empty block.
         // fold("while(x()){x}", "while(x());");
-        // fold("while(x()){x()}", "while(x())x()");
+        fold("while(x()){x()}", "while(x())x()");
         // fold("for(x=0;x<100;x++){x}", "for(x=0;x<100;x++);");
         // fold("for(x in y){x}", "for(x in y);");
         // fold("for (x of y) {x}", "for(x of y);");
-        // fold_same("for (let x = 1; x <10; x++ ) {}");
-        // fold_same("for (var x = 1; x <10; x++ ) {}");
+        fold("for (let x = 1; x <10; x++ ) {}", "for (let x = 1; x <10; x++ );");
+        fold("for (var x = 1; x <10; x++ ) {}", "for (var x = 1; x <10; x++ );");
     }
 
     #[test]

diff --git a/tasks/minsize/minsize.snap b/tasks/minsize/minsize.snap
@@ -4,19 +4,19 @@ Original   | Minified   | esbuild    | Gzip       | esbuild
 
 173.90 kB  | 61.67 kB   | 59.82 kB   | 19.54 kB   | 19.33 kB   | moment.js 
 
-287.63 kB  | 92.70 kB   | 90.07 kB   | 32.27 kB   | 31.95 kB   | jquery.js 
+287.63 kB  | 92.70 kB   | 90.07 kB   | 32.26 kB   | 31.95 kB   | jquery.js 
 
 342.15 kB  | 121.90 kB  | 118.14 kB  | 44.59 kB   | 44.37 kB   | vue.js    
 
-544.10 kB  | 73.49 kB   | 72.48 kB   | 26.13 kB   | 26.20 kB   | lodash.js 
+544.10 kB  | 73.48 kB   | 72.48 kB   | 26.12 kB   | 26.20 kB   | lodash.js 
 
 555.77 kB  | 276.49 kB  | 270.13 kB  | 91.15 kB   | 90.80 kB   | d3.js     
 
 1.01 MB    | 467.63 kB  | 458.89 kB  | 126.75 kB  | 126.71 kB  | bundle.min.js
 
 1.25 MB    | 662.86 kB  | 646.76 kB  | 164.00 kB  | 163.73 kB  | three.js  
 
-2.14 MB    | 741.57 kB  | 724.14 kB  | 181.47 kB  | 181.07 kB  | victory.js
+2.14 MB    | 741.57 kB  | 724.14 kB  | 181.45 kB  | 181.07 kB  | victory.js
 
 3.20 MB    | 1.02 MB    | 1.01 MB    | 332.01 kB  | 331.56 kB  | echarts.js