feat(minifier): merge statements after terminating if block branches (#26667)

extend minification of exit-point to handle `if` consequent that are
block statements ending in a terminating statement.

```js
if (a()) { b(); return; } c();
//              ^~~~~~~   ^~~~ move remaining stmts to else branch and remove jump stmt
if (a()) b(); else c();
// now we can collapse it to ternary if enabled
a() ? b() : c();
```

fixes #25489

crates/oxc_minifier/src/peephole/minimize_statements.rs

@@ -582,9 +582,13 @@ impl<'a> PeepholeOptimizations {
                 ctx.drop_statement(&previous.consequent);
             }
 
-            if if_stmt.consequent.is_jump_statement()
-                && Self::can_remove_termination_statement(&if_stmt.consequent, ctx)
-            {
+            let can_merge_with_alternate = match &if_stmt.consequent {
+                Statement::BlockStatement(block) => block.body.last().is_some_and(|last_stmt| {
+                    Self::can_remove_termination_statement(last_stmt, ctx)
+                }),
+                stmt => Self::can_remove_termination_statement(stmt, ctx),
+            };
+            if can_merge_with_alternate {
                 // Don't do this transformation if the branch condition could
                 // potentially access symbols declared later on on this scope below.
                 // If so, inverting the branch condition and nesting statements after
@@ -609,20 +613,34 @@ impl<'a> PeepholeOptimizations {
                     } else {
                         ArenaVec::from_iter_in(drained_stmts, ctx)
                     };
-
+                    let span = if body.is_empty() { SPAN } else { body[0].span() };
                     Self::minimize_statements(&mut body, ctx);
-                    let span =
-                        if body.is_empty() { if_stmt.consequent.span() } else { body[0].span() };
-                    ctx.replace_expression_with(&mut if_stmt.test, |test, ctx| {
-                        Self::minimize_not(test.span(), test, ctx, true)
-                    });
-                    let consequent = if body.len() == 1 {
+                    let alternate = if body.len() == 1 {
                         body.remove(0)
                     } else {
                         let scope_id = ctx.create_child_scope_of_current(ScopeFlags::empty());
                         Statement::new_block_statement_with_scope_id(span, body, scope_id, ctx)
                     };
-                    ctx.replace_statement(&mut if_stmt.consequent, consequent);
+
+                    if let Statement::BlockStatement(block) = &mut if_stmt.consequent {
+                        ctx.drop_statement(&block.body.pop().unwrap());
+                        // after removal check if there is one remaining stmt and if it requires block
+                        // IfStatement is excluded as we would add it afterward in `try_minimize_if`
+                        if block.body.len() == 1
+                            && !matches!(&block.body[0], Statement::IfStatement(_))
+                            && !Self::statement_cares_about_scope(&block.body[0])
+                        {
+                            let new_stmt = block.body.remove(0);
+                            ctx.replace_statement(&mut if_stmt.consequent, new_stmt);
+                        }
+                        if_stmt.alternate = Some(alternate);
+                    } else {
+                        ctx.replace_expression_with(&mut if_stmt.test, |test, ctx| {
+                            Self::minimize_not(test.span(), test, ctx, true)
+                        });
+                        ctx.replace_statement(&mut if_stmt.consequent, alternate);
+                    }
+
                     let mut if_stmt = Statement::IfStatement(if_stmt);
                     Self::try_minimize_if(&mut if_stmt, ctx);
                     ctx.notice_change();

crates/oxc_minifier/tests/peephole/esbuild.rs

@@ -211,7 +211,7 @@ fn js_parser_test() {
     test("while (x) { debugger; if (1) { if (1) continue; z() } }", "for (; x; ) debugger;");
     // test("while (x()) continue", "for (; x(); ) ;");
     test("while (x) { y(); continue }", "for (; x; ) y();");
-    test("while (x) { if (y) { z(); continue } }", "for (; x; ) if (y) { z(); continue; }");
+    test("while (x) { if (y) { z(); continue } }", "for (; x;) y && z();");
     test(
         "label: while (x) while (y) { z(); continue label }",
         "label: for (; x; ) for (; y; ) { z(); continue label;}",

crates/oxc_minifier/tests/peephole/minimize_exit_points.rs

@@ -62,7 +62,7 @@ fn test_function_return_optimization() {
     test("function f(){if(x)return; x=3; return; }", "function f(){ x||=3;}");
     test("function f(){if(true){a();return;}else;b();}", "function f(){a();}");
     test("function f(){if(false){a();return;}else;b();return;}", "function f(){b();}");
-    test("function f(){if(a()){b();return;}else;c();}", "function f(){if(a()){b();return}c()}"); // function f(){a()?b():c()}
+    test("function f(){if(a()){b();return;}else;c();}", "function f(){a()?b():c()}");
     test(
         "function f(){if(a()){b()}else{c();return;}}",
         "function f(){if(a())b();else{c();return}}",
@@ -73,13 +73,13 @@ fn test_function_return_optimization() {
     );
     test(
         "function f(){if(a()){if(b()){d();return;}else{return;}}else{return;} c();}",
-        "function f(){if(a()){if(b()){d();return}return}}",
-    ); // function f(){a()&&b()&&d()}
+        "function f(){a()&&b()&&d()}",
+    );
     test(
         "function f(a,b,c){if(a){}else if(b){x();return}else if(c){y();return}z()}",
         "function f(a,b,c){if(!a){if(b){x();return}if(c){y();return}}z()}",
     );
-    test("function f(){if(a()){b();return;}else;}", "function f(){if(a()){b();return}}"); // function f(){a()&&b()}
+    test("function f(){if(a()){b();return;}else;}", "function f(){a()&&b()}");
     test("function f(){if(a()){return;}else{return;} return;}", "function f(){a();}");
     test("function f(){if(a()){return;}else{return;} b();}", "function f(){a()}");
     test(
@@ -170,15 +170,15 @@ fn test_while_continue_optimization() {
     test("while(true){a();continue;b();}", "for(;;)a();");
     test("while(true){if(true){a();continue;}else;b();}", "for(;;)a();");
     test("while(true){if(false){a();continue;}else;b();continue;}", "for(;;)b();");
-    test("while(true){if(a()){b();continue;}else;c();}", "for(;;){if(a()){b();continue}c()}"); // for(;;)a()?b():c();
+    test("while(true){if(a()){b();continue;}else;c();}", "for(;;)a()?b():c()");
     test("while(true){if(a()){b();}else{c();continue;}}", "for(;;)if(a())b();else{c();continue}"); // for(;;)a()?b():c();
-    test("while(true){if(a()){b();continue;}else;}", "for (;;) if(a()){b();continue;}"); // for(;;)a()&&b();
+    test("while(true){if(a()){b();continue;}else;}", "for(;;)a()&&b()");
     test("while(true){if(a()){continue;}else{continue;} continue;}", "for(;;)a();");
     test("while(true){if(a()){continue;}else{continue;} b();}", "for(;;)a();");
     test(
         "while(true){d();if(a()){continue;}else if(b()){c();continue;}else{continue;}}",
-        "for(;;)if(d(),!a()&&b()){c();continue}",
-    ); // for(;;)d(),!a()&&b()&&c();
+        "for(;;)d(),!a()&&b()&&c()",
+    );
 
     test("while(true)while(a())continue;", "for(;;)for(;a();)continue;"); // for(;;)for(;a(););
     test("while(true)for(x in a())continue", "for(;;)for(x in a())continue;"); // for(;;)for(x in a());
@@ -215,12 +215,12 @@ fn test_do_continue_optimization() {
     test("do{a();continue;b()}while(true)", "do a();while(1)");
     test("do{if(true){a();continue;}else;b();}while(true)", "do a();while(1)");
     test("do{if(false){a();continue;}else;b();continue;}while(true)", "do b();while(1)");
-    test("do{if(a()){b();continue;}else;c();}while(true)", "do{if(a()){b();continue}c()}while(1);"); // do a()?b():c();while(1)
+    test("do{if(a()){b();continue;}else;c();}while(true)", "do a()?b():c();while(1)");
     test(
         "do{if(a()){b();}else{c();continue;}}while(true)",
         "do if(a())b();else{c();continue}while(1);",
     ); // do a()?b():c();while(1)
-    test("do{if(a()){b();continue;}else;}while(true)", "do if(a()){b();continue}while(1);"); // do a()&&b();while(1)
+    test("do{if(a()){b();continue;}else;}while(true)", "do a()&&b();while(1)");
     test("do{if(a()){continue;}else{continue;} continue;}while(true)", "do a();while(1)");
     test("do{if(a()){continue;}else{continue;} b();}while(true)", "do a();while(1)");
 
@@ -265,7 +265,7 @@ fn test_for_continue_optimization() {
     test("for(x in y){a();continue;b()}", "for(x in y)a()");
     test("for(x in y){if(true){a();continue;}else;b();}", "for(x in y)a()");
     test("for(x in y){if(false){a();continue;}else;b();continue;}", "for(x in y)b()");
-    test("for(x in y){if(a()){b();continue;}else;c();}", "for(x in y){if(a()){b();continue}c()}"); // for(x in y)a()?b():c()
+    test("for(x in y){if(a()){b();continue;}else;c();}", "for(x in y)a()?b():c()"); // for(x in y)a()?b():c()
     test(
         "for(x in y){if(a()){b();}else{c();continue;}}",
         "for(x in y)if(a())b();else{c();continue}",
@@ -275,7 +275,7 @@ fn test_for_continue_optimization() {
     test("for(x of y){a();continue;b()}", "for(x of y)a()");
     test("for(x of y){if(true){a();continue;}else;b();}", "for(x of y)a()");
     test("for(x of y){if(false){a();continue;}else;b();continue;}", "for(x of y)b()");
-    test("for(x of y){if(a()){b();continue;}else;c();}", "for(x of y){if(a()){b();continue}c()}"); // for(x of y)a()?b():c()
+    test("for(x of y){if(a()){b();continue;}else;c();}", "for(x of y)a()?b():c()");
     test(
         "for(x of y){if(a()){b();}else{c();continue;}}",
         "for(x of y)if(a())b();else{c();continue}",
@@ -299,14 +299,14 @@ fn test_for_continue_optimization() {
     );
     test(
         "r=async () => { for await (x of y){if(a()){b();continue;}else;c();}}",
-        "r=async () => { for await (x of y){if(a()){b();continue}c()}};",
-    ); // r=async () => { for await(x of y)a()?b():c()};
+        "r=async () => { for await(x of y)a()?b():c()}",
+    );
     test(
         "r=async () => { for await (x of y){if(a()){b();}else{c();continue;}}}",
-        "r=async() => { for await(x of y)if(a())b();else{c();continue}};",
+        "r=async() => { for await(x of y)if(a())b();else{c();continue}}",
     ); // r=async () => { for await (x of y) a() ? b() : c() };
 
-    test("for(x=0;x<y;x++){if(a()){b();continue;}else;}", "for(x=0;x<y;x++)if(a()){b();continue}"); // for(x=0;x<y;x++)a()&&b()
+    test("for(x=0;x<y;x++){if(a()){b();continue;}else;}", "for(x=0;x<y;x++)a()&&b()");
     test("for(x=0;x<y;x++){if(a()){continue;}else{continue;} continue;}", "for(x=0;x<y;x++)a()");
     test("for(x=0;x<y;x++){if(a()){continue;}else{continue;} b();}", "for(x=0;x<y;x++)a();");
 

tasks/minsize/minsize.snap

@@ -3,25 +3,25 @@ Original   | minified   | minified   | gzip       | gzip       | Iterations | Fi
 -------------------------------------------------------------------------------------
 72.14 kB   | 22.48 kB   | 23.70 kB   | 8.19 kB    | 8.54 kB    |          2 | react.development.js
 
-173.90 kB  | 55.50 kB   | 59.82 kB   | 18.77 kB   | 19.33 kB   |          2 | moment.js
+173.90 kB  | 55.49 kB   | 59.82 kB   | 18.78 kB   | 19.33 kB   |          2 | moment.js
 
-287.63 kB  | 89.01 kB   | 90.07 kB   | 30.86 kB   | 31.95 kB   |          2 | jquery.js
+287.63 kB  | 88.98 kB   | 90.07 kB   | 30.85 kB   | 31.95 kB   |          2 | jquery.js
 
-342.15 kB  | 114.80 kB  | 118.14 kB  | 42.70 kB   | 44.37 kB   |          2 | vue.js
+342.15 kB  | 114.76 kB  | 118.14 kB  | 42.69 kB   | 44.37 kB   |          2 | vue.js
 
-544.10 kB  | 69.88 kB   | 72.48 kB   | 25.58 kB   | 26.20 kB   |          2 | lodash.js
+544.10 kB  | 69.87 kB   | 72.48 kB   | 25.58 kB   | 26.20 kB   |          2 | lodash.js
 
-555.77 kB  | 262.75 kB  | 270.13 kB  | 87.66 kB   | 90.80 kB   |          2 | d3.js
+555.77 kB  | 262.73 kB  | 270.13 kB  | 87.66 kB   | 90.80 kB   |          2 | d3.js
 
-1.01 MB    | 435.99 kB  | 458.89 kB  | 121.78 kB  | 126.71 kB  |          2 | bundle.min.js
+1.01 MB    | 435.91 kB  | 458.89 kB  | 121.78 kB  | 126.71 kB  |          2 | bundle.min.js
 
-1.25 MB    | 634.38 kB  | 646.76 kB  | 158.43 kB  | 163.73 kB  |          2 | three.js
+1.25 MB    | 634.24 kB  | 646.76 kB  | 158.44 kB  | 163.73 kB  |          2 | three.js
 
-2.14 MB    | 707.63 kB  | 724.14 kB  | 160.08 kB  | 181.07 kB  |          2 | victory.js
+2.14 MB    | 707.61 kB  | 724.14 kB  | 160.07 kB  | 181.07 kB  |          2 | victory.js
 
-3.20 MB    | 958.82 kB  | 1.01 MB    | 317.06 kB  | 331.56 kB  |          2 | echarts.js
+3.20 MB    | 958.47 kB  | 1.01 MB    | 317.02 kB  | 331.56 kB  |          2 | echarts.js
 
-6.69 MB    | 2.12 MB    | 2.31 MB    | 453.41 kB  | 488.28 kB  |          4 | antd.js
+6.69 MB    | 2.12 MB    | 2.31 MB    | 453.40 kB  | 488.28 kB  |          4 | antd.js
 
-10.95 MB   | 3.31 MB    | 3.49 MB    | 849.97 kB  | 915.50 kB  |          4 | typescript.js
+10.95 MB   | 3.31 MB    | 3.49 MB    | 849.87 kB  | 915.50 kB  |          4 | typescript.js
 

tasks/track_memory_allocations/allocs_minifier.yaml

@@ -5,7 +5,7 @@ checker.ts:
   sys deallocs: 122
   sys alloc bytes: 14996287 # 15.00 MB
   sys peak growth: 10169560 # 10.17 MB
-  arena allocs: 56201
+  arena allocs: 56225
   arena reallocs: 5084
   arena size: 16317568 # 16.32 MB
 
@@ -16,7 +16,7 @@ App.tsx:
   sys deallocs: 61
   sys alloc bytes: 2128539 # 2.13 MB
   sys peak growth: 1612427 # 1.61 MB
-  arena allocs: 7449
+  arena allocs: 7474
   arena reallocs: 920
   arena size: 2683792 # 2.68 MB
 
@@ -38,9 +38,9 @@ pdf.mjs:
   sys deallocs: 2427
   sys alloc bytes: 5313795 # 5.31 MB
   sys peak growth: 3693355 # 3.69 MB
-  arena allocs: 19495
+  arena allocs: 19590
   arena reallocs: 2574
-  arena size: 5708304 # 5.71 MB
+  arena size: 5710976 # 5.71 MB
 
 antd.js:
   file size: 6686316 # 6.69 MB
@@ -49,7 +49,7 @@ antd.js:
   sys deallocs: 860
   sys alloc bytes: 29973448 # 29.97 MB
   sys peak growth: 19934725 # 19.93 MB
-  arena allocs: 181457
+  arena allocs: 181540
   arena reallocs: 34406
   arena size: 43039192 # 43.04 MB
 
@@ -60,7 +60,7 @@ binder.ts:
   sys deallocs: 33
   sys alloc bytes: 963008 # 963.01 kB
   sys peak growth: 657404 # 657.40 kB
-  arena allocs: 2919
+  arena allocs: 2922
   arena reallocs: 244
   arena size: 1074912 # 1.07 MB
 
@@ -71,6 +71,6 @@ kitchen-sink.tsx:
   sys deallocs: 1854
   sys alloc bytes: 5304252 # 5.30 MB
   sys peak growth: 3707425 # 3.71 MB
-  arena allocs: 31107
+  arena allocs: 31037
   arena reallocs: 3012
-  arena size: 8443456 # 8.44 MB
+  arena size: 8439864 # 8.44 MB