feat(minifier): minimize block statements

fixes #8708
oxc-project · Feb 3, 2025 · d42a9b2 · d42a9b2
1 parent d6d13dd
commit d42a9b2
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Showing 6 changed files with 86 additions and 38 deletions.
diff --git a/crates/oxc_minifier/src/peephole/minimize_conditions.rs b/crates/oxc_minifier/src/peephole/minimize_conditions.rs
@@ -574,10 +574,10 @@ mod test {
             "if (foo) { let bar = 1 } else { let baz = 1 }",
         );
         test_same("if (foo) { let bar = 1 } else { let baz = 1 }");
-        // test(
-        // "if (foo) { var bar = 1 } else { var baz = 1 }",
-        // "if (foo) var bar = 1; else var baz = 1;",
-        // );
+        test(
+            "if (foo) { var bar = 1 } else { var baz = 1 }",
+            "if (foo) var bar = 1; else var baz = 1;",
+        );
     }
 
     #[test]

diff --git a/crates/oxc_minifier/src/peephole/minimize_statements.rs b/crates/oxc_minifier/src/peephole/minimize_statements.rs
@@ -1,4 +1,4 @@
-use oxc_allocator::Vec;
+use oxc_allocator::{Box, Vec};
 use oxc_ast::{ast::*, Visit};
 use oxc_ecmascript::side_effects::MayHaveSideEffects;
 use oxc_span::{cmp::ContentEq, GetSpan};
@@ -440,6 +440,7 @@ impl<'a> PeepholeOptimizations {
                 }
                 result.push(Statement::ForOfStatement(for_of_stmt));
             }
+            Statement::BlockStatement(block_stmt) => self.handle_block(result, block_stmt),
             stmt => result.push(stmt),
         }
     }
@@ -473,4 +474,45 @@ impl<'a> PeepholeOptimizations {
         }
         false
     }
+
+    /// `appendIfOrLabelBodyPreservingScope`: <https://github.com/evanw/esbuild/blob/v0.24.2/internal/js_ast/js_parser.go#L9852>
+    fn handle_block(
+        &mut self,
+        result: &mut Vec<'a, Statement<'a>>,
+        block_stmt: Box<'a, BlockStatement<'a>>,
+    ) {
+        let keep_block = block_stmt.body.iter().any(Self::statement_cares_about_scope);
+        if keep_block {
+            result.push(Statement::BlockStatement(block_stmt));
+        } else {
+            result.append(&mut block_stmt.unbox().body);
+            self.mark_current_function_as_changed();
+        }
+    }
+
+    /// `statementCaresAboutScope`: <https://github.com/evanw/esbuild/blob/v0.24.2/internal/js_ast/js_parser.go#L9767>
+    fn statement_cares_about_scope(stmt: &Statement<'a>) -> bool {
+        match stmt {
+            Statement::BlockStatement(_)
+            | Statement::EmptyStatement(_)
+            | Statement::DebuggerStatement(_)
+            | Statement::ExpressionStatement(_)
+            | Statement::IfStatement(_)
+            | Statement::ForStatement(_)
+            | Statement::ForInStatement(_)
+            | Statement::ForOfStatement(_)
+            | Statement::DoWhileStatement(_)
+            | Statement::WhileStatement(_)
+            | Statement::WithStatement(_)
+            | Statement::TryStatement(_)
+            | Statement::SwitchStatement(_)
+            | Statement::ReturnStatement(_)
+            | Statement::ThrowStatement(_)
+            | Statement::BreakStatement(_)
+            | Statement::ContinueStatement(_)
+            | Statement::LabeledStatement(_) => false,
+            Statement::VariableDeclaration(decl) => !decl.kind.is_var(),
+            _ => true,
+        }
+    }
 }
diff --git a/crates/oxc_minifier/src/peephole/remove_dead_code.rs b/crates/oxc_minifier/src/peephole/remove_dead_code.rs
@@ -640,7 +640,7 @@ mod test {
         test("{{foo()}}", "foo()");
         test("{foo();{}}", "foo()");
         test("{{foo()}{}}", "foo()");
-        // test("{{foo()}{bar()}}", "foo();bar()");
+        test("{{foo()}{bar()}}", "foo(), bar()");
         test("{if(false)foo(); {bar()}}", "bar()");
         test("{if(false)if(false)if(false)foo(); {bar()}}", "bar()");
 
@@ -650,8 +650,8 @@ mod test {
         test("{ (function(){x++}) }", "");
         test("function f(){return;}", "function f(){}");
         test("function f(){return 3;}", "function f(){return 3}");
-        // test_same("function f(){if(x)return; x=3; return; }");
-        // test("{x=3;;;y=2;;;}", "x=3;y=2");
+        test("function f(){if(x)return; x=3; return; }", "function f(){if(x)return; x=3; }");
+        test("{x=3;;;y=2;;;}", "x=3, y=2");
 
         // Cases to test for empty block.
         // test("while(x()){x}", "while(x());");
@@ -662,6 +662,19 @@ mod test {
         test("for (let x = 1; x <10; x++ ) {}", "for (let x = 1; x <10; x++ );");
         test("for (var x = 1; x <10; x++ ) {}", "for (var x = 1; x <10; x++ );");
         test("do { } while (true)", "do;while(!0)");
+        test(
+            "function z(a) {
+              {
+                for (var i = 0; i < a; i++) {}
+                foo()
+              }
+              bar()
+            }",
+            "function z(a) {
+              for (var i = 0; i < a; i++);
+              foo(), bar()
+            }",
+        );
     }
 
     #[test]
@@ -802,8 +815,7 @@ mod test {
     #[test]
     fn test_fold_if_statement() {
         test("if (foo) {}", "foo");
-        // FIXME
-        // test("if (foo) {} else {}", "foo");
+        test("if (foo) {} else {}", "foo");
         test("if (false) {}", "");
         test("if (true) {}", "");
     }

diff --git a/crates/oxc_minifier/src/peephole/statement_fusion.rs b/crates/oxc_minifier/src/peephole/statement_fusion.rs
@@ -83,14 +83,13 @@ mod test {
     }
 
     #[test]
-    #[ignore]
     fn fuse_into_block() {
         test("a;b;c;{d;e;f}", "a,b,c,d,e,f");
-        test(
-            "a;b; label: { if(q) break label; bar(); }",
-            "label: { if(a,b,q) break label; bar(); }",
-        );
-        test("a;b;c;{var x;d;e;}", "a,b,c;{var x;d,e;}");
+        // test(
+        // "a;b; label: { if(q) break label; bar(); }",
+        // "label: { if(a,b,q) break label; bar(); }",
+        // );
+        test("a;b;c;{var x;d;e;}", "a,b,c;var x;d,e;");
         test("a;b;c;label:{break label;d;e;}", "a,b,c");
     }
 
@@ -110,22 +109,17 @@ mod test {
     }
 
     #[test]
-    #[ignore]
     fn no_fuse_into_block() {
         // Never fuse a statement into a block that contains let/const/class declarations, or you risk
         // colliding variable names. (unless the AST is normalized).
         test("a; {b;}", "a,b");
-        test("a; {b; var a = 1;}", "{a, b; var a = 1;}");
+        test("a; {b; var a = 1;}", "a, b; var a = 1;");
         test_same("a; { b; let a = 1; }");
         test("a; { b; const a = 1; }", "a; { b; let a = 1; }");
         test_same("a; { b; class a {} }");
         test_same("a; { b; function a() {} }");
         test("a; { b; const otherVariable = 1; }", "a; { b; let otherVariable = 1; }");
 
-        // test(
-        // "function f(a) { if (COND) { a; { b; let a = 1; } } }",
-        // "function f(a) { if (COND) { { a,b; let a$jscomp$1 = 1; } } }",
-        // );
         // test(
         // "function f(a) { if (COND) { a; { b; let otherVariable = 1; } } }",
         // "function f(a) { if (COND) {  { a,b; let otherVariable = 1; } } }",

diff --git a/crates/oxc_minifier/tests/peephole/esbuild.rs b/crates/oxc_minifier/tests/peephole/esbuild.rs
@@ -330,8 +330,8 @@ fn js_parser_test() {
     test("a = '' + true", "a = 'true';");
     test("a = false + ''", "a = 'false';");
     test("a = true + ''", "a = 'true';");
-    // test("a = 1 + false + ''", "a = 1 + false + '';");
-    // test("a = 0 + true + ''", "a = 0 + true + '';");
+    test("a = 1 + false + ''", "a = '1';");
+    test("a = 0 + true + ''", "a = '1';");
     test("a = '' + null", "a = 'null';");
     test("a = null + ''", "a = 'null';");
     test("a = '' + undefined", "a = 'undefined';");
@@ -539,12 +539,12 @@ fn js_parser_test() {
     test("a(); if (b) throw c", "if (a(), b) throw c;");
     test("if (a) if (b) throw c", "if (a && b) throw c;");
     test("if (true) { let a = b; if (c) throw d }", "{ let a = b; if (c) throw d;}");
-    // test("if (true) { if (a) throw b; if (c) throw d }", "if (a) throw b;if (c) throw d;");
-    // test("if (false) throw a; else { let b = c; if (d) throw e }", "{ let b = c; if (d) throw e;}");
-    // test(
-    // "if (false) throw a; else { if (b) throw c; if (d) throw e }",
-    // "if (b) throw c;if (d) throw e;",
-    // );
+    test("if (true) { if (a) throw b; if (c) throw d }", "if (a) throw b;if (c) throw d;");
+    test("if (false) throw a; else { let b = c; if (d) throw e }", "{ let b = c; if (d) throw e;}");
+    test(
+        "if (false) throw a; else { if (b) throw c; if (d) throw e }",
+        "if (b) throw c;if (d) throw e;",
+    );
     test(
         "if (a) { if (b) throw c; else { let d = e; if (f) throw g } }",
         "if (a) { if (b) throw c; { let d = e; if (f) throw g; }}",

diff --git a/tasks/minsize/minsize.snap b/tasks/minsize/minsize.snap
@@ -1,27 +1,27 @@
            | Oxc        | ESBuild    | Oxc        | ESBuild    |
 Original   | minified   | minified   | gzip       | gzip       | Fixture
 -------------------------------------------------------------------------------------
-72.14 kB   | 23.56 kB   | 23.70 kB   | 8.50 kB    | 8.54 kB    | react.development.js
+72.14 kB   | 23.51 kB   | 23.70 kB   | 8.47 kB    | 8.54 kB    | react.development.js
 
 173.90 kB  | 59.55 kB   | 59.82 kB   | 19.18 kB   | 19.33 kB   | moment.js 
 
 287.63 kB  | 89.45 kB   | 90.07 kB   | 30.97 kB   | 31.95 kB   | jquery.js 
 
-342.15 kB  | 117.67 kB  | 118.14 kB  | 43.48 kB   | 44.37 kB   | vue.js    
+342.15 kB  | 117.62 kB  | 118.14 kB  | 43.45 kB   | 44.37 kB   | vue.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  | 88.33 kB   | 90.80 kB   | d3.js     
+555.77 kB  | 271.20 kB  | 270.13 kB  | 88.30 kB   | 90.80 kB   | d3.js     
 
-1.01 MB    | 440.93 kB  | 458.89 kB  | 122.53 kB  | 126.71 kB  | bundle.min.js
+1.01 MB    | 440.93 kB  | 458.89 kB  | 122.52 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    | 717.07 kB  | 724.14 kB  | 162.05 kB  | 181.07 kB  | victory.js
+2.14 MB    | 717.02 kB  | 724.14 kB  | 162.02 kB  | 181.07 kB  | victory.js
 
-3.20 MB    | 1.01 MB    | 1.01 MB    | 324.40 kB  | 331.56 kB  | echarts.js
+3.20 MB    | 1.01 MB    | 1.01 MB    | 324.33 kB  | 331.56 kB  | echarts.js
 
-6.69 MB    | 2.28 MB    | 2.31 MB    | 467.77 kB  | 488.28 kB  | antd.js   
+6.69 MB    | 2.28 MB    | 2.31 MB    | 467.74 kB  | 488.28 kB  | antd.js   
 
-10.95 MB   | 3.36 MB    | 3.49 MB    | 862.00 kB  | 915.50 kB  | typescript.js
+10.95 MB   | 3.36 MB    | 3.49 MB    | 861.78 kB  | 915.50 kB  | typescript.js