perf: replace empty functions with noopQrl

packages/qwik/src/optimizer/core/src/parse.rs

@@ -311,11 +311,32 @@ pub fn transform_code(config: TransformCodeOptions) -> Result<TransformOutput, a
 							&config.core_module,
 						);
 
+						let mut treeshaker = Treeshaker::new();
+
 						// replace const values
 						if config.mode != EmitMode::Test {
 							let mut const_replacer =
 								ConstReplacerVisitor::new(config.is_server, is_dev, &collect);
 							program.visit_mut_with(&mut const_replacer);
+
+							if config.minify != MinifyMode::None {
+								if !config.is_server {
+									// remove all side effects from client, step 1
+									program.visit_mut_with(&mut treeshaker.marker);
+								}
+
+								// simplify & strip unused code before segmenting
+								program = program.fold_with(&mut simplify::simplifier(
+									unresolved_mark,
+									simplify::Config {
+										dce: simplify::dce::Config {
+											preserve_imports_with_side_effects: false,
+											..Default::default()
+										},
+										..Default::default()
+									},
+								));
+							}
 						}
 
 						// split into segments
@@ -338,14 +359,8 @@ pub fn transform_code(config: TransformCodeOptions) -> Result<TransformOutput, a
 						});
 						program = program.fold_with(&mut qwik_transform);
 
-						let mut treeshaker = Treeshaker::new();
 						if config.minify != MinifyMode::None {
-							// remove all side effects from client, step 1
-							if !config.is_server {
-								program.visit_mut_with(&mut treeshaker.marker);
-							}
-
-							// simplify & strip unused code
+							// simplify & strip unused code, again
 							program = program.fold_with(&mut simplify::simplifier(
 								unresolved_mark,
 								simplify::Config {
@@ -357,6 +372,7 @@ pub fn transform_code(config: TransformCodeOptions) -> Result<TransformOutput, a
 								},
 							));
 						}
+
 						if matches!(
 							config.entry_strategy,
 							EntryStrategy::Inline | EntryStrategy::Hoist

packages/qwik/src/optimizer/core/src/snapshots/qwik_core__test__empty_fn_to_noop.snap

@@ -0,0 +1,40 @@
+---
+source: packages/qwik/src/optimizer/core/src/test.rs
+assertion_line: 3565
+expression: output
+---
+==INPUT==
+
+
+		import { isServer } from '@builder.io/qwik/build';
+		import { component$ } from '@builder.io/qwik';
+		export const Cmp0 = component$(() => {
+			return undefined;
+		 });
+		export const Cmp1 = component$(() => {
+			if (!isServer) {
+				return <div>hello</div>;
+			}
+		});
+		export const Cmp2 = component$(function(_unused) {
+			if (isServer) {
+				return;
+			}
+			return <div>hello</div>;
+		});
+		export const Cmp3 = component$(function() { });
+
+============================= test.tsx ==
+
+import { componentQrl } from "@builder.io/qwik";
+import { _noopQrl } from "@builder.io/qwik";
+export const Cmp0 = /*#__PURE__*/ componentQrl(/*#__PURE__*/ _noopQrl("s_SEk00MbyDzs"));
+export const Cmp1 = /*#__PURE__*/ componentQrl(/*#__PURE__*/ _noopQrl("s_U2t03012214"));
+export const Cmp2 = /*#__PURE__*/ componentQrl(/*#__PURE__*/ _noopQrl("s_FnOz26iMYaM"));
+export const Cmp3 = /*#__PURE__*/ componentQrl(/*#__PURE__*/ _noopQrl("s_wyGQRm5AyHM"));
+
+
+Some("{\"version\":3,\"sources\":[\"/user/qwik/src/test.tsx\"],\"names\":[],\"mappings\":\";;AAGE,OAAO,MAAM,qBAAO,sDAEhB;AACJ,OAAO,MAAM,qBAAO,sDAIjB;AACH,OAAO,MAAM,qBAAO,sDAKjB;AACH,OAAO,MAAM,qBAAO,sDAA2B\"}")
+== DIAGNOSTICS ==
+
+[]

packages/qwik/src/optimizer/core/src/snapshots/qwik_core__test__example_strip_client_code.snap

@@ -26,7 +26,7 @@ export const Parent = component$(() => {
     });
 
     useTask$(() => {
-        // Code
+        runSomething();
     });
 
     return (
@@ -67,7 +67,7 @@ export const Parent = /*#__PURE__*/ componentQrl(/*#__PURE__*/ inlinedQrl(()=>{
         state
     ]));
     useTaskQrl(/*#__PURE__*/ inlinedQrl(()=>{
-    // Code
+        runSomething();
     }, "Parent_component_useTask_ngmvcygWux8"));
     return /*#__PURE__*/ _jsxQ("div", null, {
         shouldRemove$: /*#__PURE__*/ _noopQrl("Parent_component_div_shouldRemove_EBj69wTX1do", [
@@ -97,7 +97,7 @@ export const Parent = /*#__PURE__*/ componentQrl(/*#__PURE__*/ inlinedQrl(()=>{
 }, "Parent_component_t6Wy3C0Q0XM"));
 
 
-Some("{\"version\":3,\"sources\":[\"/user/qwik/src/components/component.tsx\"],\"names\":[],\"mappings\":\";;;;;;;;;;;;AACA,SAAsC,QAAQ,QAAkB,mBAAmB;AAQnF,OAAO,MAAM,uBAAS,sCAAW;IAC7B,MAAM,QAAQ,SAAS;QACnB,MAAM;IACV;IAEA,qBAAqB;IACrB;;;IAKA,oCAAS;IACL,OAAO;IACX;IAEA,qBACI,MAAC;QACG,aAAa;;;QACb,QAAQ;;;;sBAER,MAAC;YACG,QAAQ,2BAAE,IAAM,QAAQ,GAAG,CAAC;YAC5B,OAAO,2BAAE;;uBAAM,MAAM,IAAI;;;;;gBADzB,QAAQ;gBACR,OAAO;;;wBAEV,GAAM,IAAI;;;;AAGvB,oCAAG\"}")
+Some("{\"version\":3,\"sources\":[\"/user/qwik/src/components/component.tsx\"],\"names\":[],\"mappings\":\";;;;;;;;;;;;AACA,SAAsC,QAAQ,QAAkB,mBAAmB;AAQnF,OAAO,MAAM,uBAAS,sCAAW;IAC7B,MAAM,QAAQ,SAAS;QACnB,MAAM;IACV;IAEA,qBAAqB;IACrB;;;IAKA,oCAAS;QACL;IACJ;IAEA,qBACI,MAAC;QACG,aAAa;;;QACb,QAAQ;;;;sBAER,MAAC;YACG,QAAQ,2BAAE,IAAM,QAAQ,GAAG,CAAC;YAC5B,OAAO,2BAAE;;uBAAM,MAAM,IAAI;;;;;gBADzB,QAAQ;gBACR,OAAO;;;wBAEV,GAAM,IAAI;;;;AAGvB,oCAAG\"}")
 == DIAGNOSTICS ==
 
 []

packages/qwik/src/optimizer/core/src/snapshots/qwik_core__test__example_strip_server_code.snap

@@ -27,18 +27,18 @@ export const Parent = component$(() => {
     serverStuff$(async () => {
         // should be removed too
         const a = $(() => {
-            // from $(), should not be removed
+            dontRemoveThisDollar();
         });
         const b = client$(() => {
-            // from clien$(), should not be removed
+            dontRemoveThisClient();
         });
         return [a,b];
     })
 
     serverLoader$(handler);
 
     useTask$(() => {
-        // Code
+        runSomething();
     });
 
     return (
@@ -95,12 +95,12 @@ Some("{\"version\":3,\"sources\":[\"/user/qwik/src/test.tsx\"],\"names\":[],\"ma
 ============================= test.tsx_parent_component_serverstuff_a_2ca3hldc7yc.js (ENTRY POINT)==
 
 export const Parent_component_serverStuff_a_2ca3HLDC7yc = ()=>{
-// from $(), should not be removed
+    dontRemoveThisDollar();
 };
 export { _hW } from "@builder.io/qwik";
 
 
-Some("{\"version\":3,\"sources\":[\"/user/qwik/src/test.tsx\"],\"names\":[],\"mappings\":\"0DAqBoB;AACR,kCAAkC;AACtC\"}")
+Some("{\"version\":3,\"sources\":[\"/user/qwik/src/test.tsx\"],\"names\":[],\"mappings\":\"0DAqBoB;IACR;AACJ\"}")
 /*
 {
   "origin": "test.tsx",
@@ -117,18 +117,18 @@ Some("{\"version\":3,\"sources\":[\"/user/qwik/src/test.tsx\"],\"names\":[],\"ma
   "captures": false,
   "loc": [
     602,
-    666
+    655
   ]
 }
 */
 ============================= test.tsx_parent_component_serverstuff_b_client_v9qawr2inkk.js (ENTRY POINT)==
 
 export const Parent_component_serverStuff_b_client_v9qawr2Inkk = ()=>{
-// from clien$(), should not be removed
+    dontRemoveThisClient();
 };
 
 
-Some("{\"version\":3,\"sources\":[\"/user/qwik/src/test.tsx\"],\"names\":[],\"mappings\":\"iEAwB0B;AACd,uCAAuC;AAC3C\"}")
+Some("{\"version\":3,\"sources\":[\"/user/qwik/src/test.tsx\"],\"names\":[],\"mappings\":\"iEAwB0B;IACd;AACJ\"}")
 /*
 {
   "origin": "test.tsx",
@@ -144,8 +144,8 @@ Some("{\"version\":3,\"sources\":[\"/user/qwik/src/test.tsx\"],\"names\":[],\"ma
   "ctxName": "client$",
   "captures": false,
   "loc": [
-    695,
-    764
+    684,
+    737
   ]
 }
 */
@@ -195,7 +195,7 @@ Some("{\"version\":3,\"sources\":[\"/user/qwik/src/test.tsx\"],\"names\":[],\"ma
   "captures": false,
   "loc": [
     289,
-    986
+    967
   ]
 }
 */
@@ -220,20 +220,20 @@ Some("{\"version\":3,\"sources\":[\"/user/qwik/src/test.tsx\"],\"names\":[],\"ma
   "ctxName": "onClick$",
   "captures": false,
   "loc": [
-    908,
-    935
+    889,
+    916
   ]
 }
 */
 ============================= test.tsx_parent_component_usetask_1_p8orqhhsurk.js (ENTRY POINT)==
 
 export const Parent_component_useTask_1_P8oRQhHsurk = ()=>{
-// Code
+    runSomething();
 };
 export { _hW } from "@builder.io/qwik";
 
 
-Some("{\"version\":3,\"sources\":[\"/user/qwik/src/test.tsx\"],\"names\":[],\"mappings\":\"sDAgCa;AACL,OAAO;AACX\"}")
+Some("{\"version\":3,\"sources\":[\"/user/qwik/src/test.tsx\"],\"names\":[],\"mappings\":\"sDAgCa;IACL;AACJ\"}")
 /*
 {
   "origin": "test.tsx",
@@ -249,8 +249,8 @@ Some("{\"version\":3,\"sources\":[\"/user/qwik/src/test.tsx\"],\"names\":[],\"ma
   "ctxName": "useTask$",
   "captures": false,
   "loc": [
-    839,
-    868
+    812,
+    849
   ]
 }
 */

packages/qwik/src/optimizer/core/src/test.rs

@@ -1731,18 +1731,18 @@ export const Parent = component$(() => {
     serverStuff$(async () => {
         // should be removed too
         const a = $(() => {
-            // from $(), should not be removed
+            dontRemoveThisDollar();
         });
         const b = client$(() => {
-            // from clien$(), should not be removed
+            dontRemoveThisClient();
         });
         return [a,b];
     })
 
     serverLoader$(handler);
 
     useTask$(() => {
-        // Code
+        runSomething();
     });
 
     return (
@@ -1836,7 +1836,7 @@ export const Parent = component$(() => {
     });
 
     useTask$(() => {
-        // Code
+        runSomething();
     });
 
     return (
@@ -3592,6 +3592,35 @@ fn impure_template_fns() {
 	});
 }
 
+#[test]
+fn empty_fn_to_noop() {
+	test_input!(TestInput {
+		code: r#"
+		import { isServer } from '@builder.io/qwik/build';
+		import { component$ } from '@builder.io/qwik';
+		export const Cmp0 = component$(() => {
+			return undefined;
+		 });
+		export const Cmp1 = component$(() => {
+			if (!isServer) {
+				return <div>hello</div>;
+			}
+		});
+		export const Cmp2 = component$(function(_unused) {
+			if (isServer) {
+				return;
+			}
+			return <div>hello</div>;
+		});
+		export const Cmp3 = component$(function() { });
+		"#
+		.to_string(),
+		mode: EmitMode::Prod,
+		is_server: Some(true),
+		..TestInput::default()
+	});
+}
+
 // TODO(misko): Make this test work by implementing strict serialization.
 // #[test]
 // fn example_of_synchronous_qrl_that_cant_be_serialized() {

packages/qwik/src/optimizer/core/src/transform.rs

@@ -624,6 +624,7 @@ impl<'a> QwikTransform<'a> {
 		self.segment_stack.push(symbol_name.clone());
 		let span = first_arg.span();
 		let folded = first_arg.fold_with(self);
+		let is_empty = is_empty_function(&folded);
 		self.segment_stack.pop();
 
 		// Collect local idents
@@ -657,7 +658,7 @@ impl<'a> QwikTransform<'a> {
 			need_transform: true,
 			hash,
 		};
-		let should_emit = self.should_emit_segment(&segment_data);
+		let should_emit = !is_empty && self.should_emit_segment(&segment_data);
 		if should_emit {
 			for id in &segment_data.local_idents {
 				if !self.options.global_collect.exports.contains_key(id) {
@@ -2430,3 +2431,37 @@ fn is_text_only(node: &str) -> bool {
 		"text" | "textarea" | "title" | "option" | "script" | "style" | "noscript"
 	)
 }
+
+/** detect if an expression is a function or arrow function with an empty function body */
+fn is_empty_function(expr: &ast::Expr) -> bool {
+	match expr {
+		ast::Expr::Fn(ast::FnExpr {
+			function: box ast::Function {
+				body: Some(ast::BlockStmt { stmts, .. }),
+				..
+			},
+			..
+		}) => are_statements_empty(stmts),
+		ast::Expr::Arrow(ast::ArrowExpr {
+			body: box ast::BlockStmtOrExpr::BlockStmt(block),
+			..
+		}) => are_statements_empty(&block.stmts),
+		_ => false,
+	}
+}
+
+/** detect if statements are empty or only `return` or `return undefined` */
+fn are_statements_empty(stmts: &[ast::Stmt]) -> bool {
+	dbg!(stmts).is_empty()
+		|| (stmts.len() == 1
+			&& match &stmts[0] {
+				ast::Stmt::Return(ast::ReturnStmt { arg, .. }) => {
+					arg.is_none()
+						|| match &arg {
+							Some(box ast::Expr::Ident(ident)) => ident.sym == js_word!("undefined"),
+							_ => false,
+						}
+				}
+				_ => false,
+			})
+}