joining without newlines seems to work better in common cases

packages/svelte/src/compiler/migrate/index.js

@@ -786,29 +786,28 @@ function handle_events(element, state) {
 			state.str.remove(needs_line_delete ? new_line_index : node.start, node.end);
 		}
 
-		const first_node = nodes[0];
+		const first = nodes[0];
-
+
-		if (first_node) {
+		if (first) {
-			const indent = get_indent(state, first_node, element);
+			const indent = get_indent(state, first, element);
-			let handlers_body = '';
+
-			for (const handler of handlers) {
+			let singular = handlers.map((handler) => handler.handler).join(', ');
-				handlers_body += `${handler.needs_line_delete || nodes.length > 1 ? `\n${indent}` : ''}${handler.handler},`;
+
-			}
+			if (singular) {
-			handlers_body = handlers_body.substring(0, handlers_body.length - 1);
+				if (singular === name) {
-			if (handlers_body) {
+					state.str.overwrite(first.start, first.end, `{${name}}`);
-				if (handlers_body === name) {
-					state.str.overwrite(first_node.start, first_node.end, `{${name}}`);
 				} else {
-					state.str.overwrite(
+					if (nodes.length > 1) {
-						first_node.start,
+						singular = `${state.names.handlers}(${singular})`;
-						first_node.end,
-						`${name}={${nodes.length > 1 ? `${state.names.handlers}(` : ''}${handlers_body}${nodes.length > 1 ? ')' : ''}}`
-					);
 					}
+
+					state.str.overwrite(first.start, first.end, `${name}={${singular}}`);
 				}
+			}
+
 			for (const passive_handler of explicit_passive_handlers) {
 				state.str.appendRight(
-					first_node.end,
+					first.end,
 					`${passive_handler.needs_line_delete || nodes.length > 1 ? `\n${indent}` : ''}${passive_handler.handler}`
 				);
 			}
@@ -822,21 +821,16 @@ function handle_events(element, state) {
  * @param {Array<{start: number; end: number}>} nodes
  */
 function get_indent(state, ...nodes) {
-	let indent = state.indent;
-
 	for (const node of nodes) {
 		const line_start = state.str.original.lastIndexOf('\n', node.start);
-		indent = state.str.original.substring(line_start + 1, node.start);
+		const indent = state.str.original.substring(line_start + 1, node.start);
 
 		if (indent.trim() === '') {
-			indent = state.indent + indent;
 			return indent;
-		} else {
-			indent = state.indent;
 		}
 	}
 
-	return indent;
+	return '';
 }
 
 /**

packages/svelte/tests/migrate/samples/event-handlers-with-alias/output.svelte

@@ -15,21 +15,12 @@
 	let nonpassive;
 </script>
 
-<button onclick={handlers_1(
+<button onclick={handlers_1(() => console.log('hi'), bubble_1('click'))} >click me</button>
-	() => console.log('hi'),
+<button onclick={handlers_1(function(){ console.log('hi') }, bubble_1('click'))} >click me</button>
-	bubble_1('click'))} >click me</button>
+<button onclick={handlers_1(() => console.log('before'), bubble_1('click'), () => console.log('after'))}  
-<button onclick={handlers_1(
-	function(){ console.log('hi') },
-	bubble_1('click'))} >click me</button>
-<button onclick={handlers_1(
-	() => console.log('before'),
-	bubble_1('click'),
-	() => console.log('after'))}  
 	>click me</button
 >
-<button onclick={handlers_1(
+<button onclick={handlers_1(bubble_1('click'), foo)} >click me</button>
-	bubble_1('click'),
-	foo)} >click me</button>
 <button onclick={bubble_1('click')}>click me</button>
 
 <button ondblclick={() => console.log('hi')}>click me</button>
@@ -63,29 +54,19 @@
 <button use:nonpassive_1={['click', () => trusted_1(()=>'')]}>click me</button>
 
 <button 
-	onclick={handlers_1(
+	onclick={handlers_1(bubble_1('click'), ()=>'')}
-		bubble_1('click'),
-		()=>'')}
 	use:passive_1={['click', () => ()=>'']}
 >click me</button>
 
 <button 
-	onclick={handlers_1(
+	onclick={handlers_1(bubble_1('click'), ()=>'')}
-		bubble_1('click'),
-		()=>'')}
 	use:nonpassive_1={['click', () => ()=>'']}
 >click me</button>
 
 
 <button
-	onclick={handlers_1(
+	onclick={handlers_1(bubble_1('click'), foo, ()=>'', once_1(trusted_1(preventDefault_1(()=>''))))}
-		bubble_1('click'),
+	onblur={handlers_1(foo, once_1(trusted_1(preventDefault_1(bubble_1('blur')))))}
-		foo,
-		()=>'',
-		once_1(trusted_1(preventDefault_1(()=>''))))}
-	onblur={handlers_1(
-		foo,
-		once_1(trusted_1(preventDefault_1(bubble_1('blur')))))}
 >
 	click me
 </button>

packages/svelte/tests/migrate/samples/event-handlers/input.svelte

@@ -46,7 +46,9 @@
 <button
 	on:click|nonpassive={()=>''}
 	on:click
-	on:click={()=>''}
+	on:click={()=>{
+		return 'multiline';
+	}}
 >click me</button>
 
 

packages/svelte/tests/migrate/samples/event-handlers/output.svelte

@@ -4,21 +4,12 @@
 	const bubble = createBubbler();
 </script>
 
-<button onclick={handlers(
+<button onclick={handlers(() => console.log('hi'), bubble('click'))} >click me</button>
-	() => console.log('hi'),
+<button onclick={handlers(function(){ console.log('hi') }, bubble('click'))} >click me</button>
-	bubble('click'))} >click me</button>
+<button onclick={handlers(() => console.log('before'), bubble('click'), () => console.log('after'))}  
-<button onclick={handlers(
-	function(){ console.log('hi') },
-	bubble('click'))} >click me</button>
-<button onclick={handlers(
-	() => console.log('before'),
-	bubble('click'),
-	() => console.log('after'))}  
 	>click me</button
 >
-<button onclick={handlers(
+<button onclick={handlers(bubble('click'), foo)} >click me</button>
-	bubble('click'),
-	foo)} >click me</button>
 <button onclick={bubble('click')}>click me</button>
 
 <button ondblclick={() => console.log('hi')}>click me</button>
@@ -53,29 +44,21 @@
 <button use:nonpassive={['click', () => trusted(()=>'')]}>click me</button>
 
 <button
-	onclick={handlers(
+	onclick={handlers(bubble('click'), ()=>'')}
-		bubble('click'),
-		()=>'')}
 	use:passive={['click', () => ()=>'']}
 >click me</button>
 
 <button
-	onclick={handlers(
+	onclick={handlers(bubble('click'), ()=>{
-		bubble('click'),
+		return 'multiline';
-		()=>'')}
+	})}
 	use:nonpassive={['click', () => ()=>'']}
 >click me</button>
 
 
 <button
-	onclick={handlers(
+	onclick={handlers(bubble('click'), foo, ()=>'', once(trusted(preventDefault(()=>''))))}
-		bubble('click'),
+	onblur={handlers(foo, once(trusted(preventDefault(bubble('blur')))))}
-		foo,
-		()=>'',
-		once(trusted(preventDefault(()=>''))))}
-	onblur={handlers(
-		foo,
-		once(trusted(preventDefault(bubble('blur')))))}
 >
 	click me
 </button>