eliminate need to pass outro callbacks around

src/compile/render-dom/Block.ts

@@ -360,12 +360,10 @@ export default class Block {
 			}
 
 			if (this.builders.outro.isEmpty()) {
-				properties.addLine(`o: @run,`);
+				properties.addLine(`o: @noop,`);
 			} else {
 				properties.addBlock(deindent`
-					${dev ? 'o: function outro' : 'o'}(#outrocallback) {
+					${dev ? 'o: function outro' : 'o'}() {
-						${this.outros > 1 && `#outrocallback = @callAfter(#outrocallback, ${this.outros});`}
-
 						${this.builders.outro}
 					},
 				`);

src/compile/render-dom/wrappers/AwaitBlock.ts

@@ -208,13 +208,10 @@ export default class AwaitBlockWrapper extends Wrapper {
 		}
 
 		if (this.pending.block.hasOutroMethod) {
-			const countdown = block.getUniqueName('countdown');
 			block.builders.outro.addBlock(deindent`
-				const ${countdown} = @callAfter(#outrocallback, 3);
 				for (let #i = 0; #i < 3; #i += 1) {
 					const block = ${info}.blocks[#i];
-					if (block) block.o(${countdown});
+					if (block) block.o();
-					else ${countdown}();
 				}
 			`);
 		}

src/compile/render-dom/wrappers/EachBlock.ts

@@ -345,13 +345,13 @@ export default class EachBlockWrapper extends Wrapper {
 			${this.node.hasAnimation && `for (let #i = 0; #i < ${blocks}.length; #i += 1) ${blocks}[#i].r();`}
 			${blocks} = @updateKeyedEach(${blocks}, $$, changed, ${get_key}, ${dynamic ? '1' : '0'}, ctx, ${this.vars.each_block_value}, ${lookup}, ${updateMountNode}, ${destroy}, ${create_each_block}, "${mountOrIntro}", ${anchor}, ${this.vars.get_each_context});
 			${this.node.hasAnimation && `for (let #i = 0; #i < ${blocks}.length; #i += 1) ${blocks}[#i].a();`}
+			${this.block.hasOutros && `@check_outros();`}
 		`);
 
 		if (this.block.hasOutros) {
 			const countdown = block.getUniqueName('countdown');
 			block.builders.outro.addBlock(deindent`
-				const ${countdown} = @callAfter(#outrocallback, ${blocks}.length);
+				for (#i = 0; #i < ${blocks}.length; #i += 1) ${blocks}[#i].o();
-				for (#i = 0; #i < ${blocks}.length; #i += 1) ${blocks}[#i].o(${countdown});
 			`);
 		}
 
@@ -415,15 +415,16 @@ export default class EachBlockWrapper extends Wrapper {
 		const outroBlock = this.block.hasOutros && block.getUniqueName('outroBlock')
 		if (outroBlock) {
 			block.builders.init.addBlock(deindent`
-				function ${outroBlock}(i, detach, fn) {
+				function ${outroBlock}(i, detach) {
 					if (${iterations}[i]) {
-						${iterations}[i].o(() => {
+						if (detach) {
-							if (detach) {
+							@on_outro(() => {
 								${iterations}[i].d(detach);
 								${iterations}[i] = null;
-							}
+							});
-							if (fn) fn();
+						}
-						});
+
+						${iterations}[i].o();
 					}
 				}
 			`);
@@ -468,6 +469,7 @@ export default class EachBlockWrapper extends Wrapper {
 				destroy = deindent`
 					@group_outros();
 					for (; #i < ${iterations}.length; #i += 1) ${outroBlock}(#i, 1);
+					@check_outros();
 				`;
 			} else {
 				destroy = deindent`
@@ -501,8 +503,7 @@ export default class EachBlockWrapper extends Wrapper {
 			const countdown = block.getUniqueName('countdown');
 			block.builders.outro.addBlock(deindent`
 				${iterations} = ${iterations}.filter(Boolean);
-				const ${countdown} = @callAfter(#outrocallback, ${iterations}.length);
+				for (let #i = 0; #i < ${iterations}.length; #i += 1) ${outroBlock}(#i, 0);`
-				for (let #i = 0; #i < ${iterations}.length; #i += 1) ${outroBlock}(#i, 0, ${countdown});`
 			);
 		}
 

src/compile/render-dom/wrappers/Element/index.ts

@@ -606,7 +606,6 @@ export default class ElementWrapper extends Wrapper {
 			block.builders.outro.addBlock(deindent`
 				if (!${name}) ${name} = @create_bidirectional_transition(${this.var}, ${fn}, ${snippet}, false);
 				${name}.run(0, () => {
-					#outrocallback();
 					${name} = null;
 				});
 			`);
@@ -659,7 +658,7 @@ export default class ElementWrapper extends Wrapper {
 				// TODO hide elements that have outro'd (unless they belong to a still-outroing
 				// group) prior to their removal from the DOM
 				block.builders.outro.addBlock(deindent`
-					${outroName} = @create_out_transition(${this.var}, ${fn}, ${snippet}, #outrocallback);
+					${outroName} = @create_out_transition(${this.var}, ${fn}, ${snippet});
 				`);
 
 				block.builders.destroy.addConditional('detach', `if (${outroName}) ${outroName}.end();`);

src/compile/render-dom/wrappers/IfBlock.ts

@@ -161,10 +161,7 @@ export default class IfBlockWrapper extends Wrapper {
 			if (hasOutros) {
 				this.renderCompoundWithOutros(block, parentNode, parentNodes, dynamic, vars);
 
-				block.builders.outro.addBlock(deindent`
+				block.builders.outro.addLine(`if (${name}) ${name}.o();`);
-					if (${name}) ${name}.o(#outrocallback);
-					else #outrocallback();
-				`);
 			} else {
 				this.renderCompound(block, parentNode, parentNodes, dynamic, vars);
 			}
@@ -172,10 +169,7 @@ export default class IfBlockWrapper extends Wrapper {
 			this.renderSimple(block, parentNode, parentNodes, dynamic, vars);
 
 			if (hasOutros) {
-				block.builders.outro.addBlock(deindent`
+				block.builders.outro.addLine(`if (${name}) ${name}.o();`);
-					if (${name}) ${name}.o(#outrocallback);
-					else #outrocallback();
-				`);
 			}
 		}
 
@@ -323,10 +317,12 @@ export default class IfBlockWrapper extends Wrapper {
 
 		const destroyOldBlock = deindent`
 			@group_outros();
-			${name}.o(function() {
+			@on_outro(() => {
 				${if_blocks}[${previous_block_index}].d(1);
 				${if_blocks}[${previous_block_index}] = null;
 			});
+			${name}.o();
+			@check_outros();
 		`;
 
 		const createNewBlock = deindent`
@@ -446,10 +442,13 @@ export default class IfBlockWrapper extends Wrapper {
 		const exit = branch.block.hasOutroMethod
 			? deindent`
 				@group_outros();
-				${name}.o(function() {
+				@on_outro(() => {
 					${name}.d(1);
 					${name} = null;
 				});
+
+				${name}.o();
+				@check_outros();
 			`
 			: deindent`
 				${name}.d(1);

src/compile/render-dom/wrappers/InlineComponent/index.ts

@@ -364,9 +364,11 @@ export default class InlineComponentWrapper extends Wrapper {
 					if (${name}) {
 						@group_outros();
 						const old_component = ${name};
-						old_component.$$.fragment.o(() => {
+						@on_outro(() => {
 							old_component.$destroy();
 						});
+						old_component.$$.fragment.o();
+						@check_outros();
 					}
 
 					if (${switch_value}) {
@@ -440,7 +442,7 @@ export default class InlineComponentWrapper extends Wrapper {
 		}
 
 		block.builders.outro.addLine(
-			`if (${name}) ${name}.$$.fragment.o(#outrocallback);`
+			`if (${name}) ${name}.$$.fragment.o();`
 		);
 	}
 

src/internal/keyed-each.js

@@ -1,12 +1,16 @@
+import { on_outro } from './transitions.js';
+
 export function destroyBlock(block, lookup) {
 	block.d(1);
 	lookup[block.key] = null;
 }
 
 export function outroAndDestroyBlock(block, lookup) {
-	block.o(function() {
+	on_outro(() => {
 		destroyBlock(block, lookup);
 	});
+
+	block.o();
 }
 
 export function fixAndOutroAndDestroyBlock(block, lookup) {

src/internal/transitions.js

@@ -24,6 +24,16 @@ export function group_outros() {
 	};
 }
 
+export function check_outros() {
+	if (!outros.remaining) {
+		run_all(outros.callbacks);
+	}
+}
+
+export function on_outro(callback) {
+	outros.callbacks.push(callback);
+}
+
 export function create_in_transition(node, fn, params) {
 	let config = fn(node, params);
 	let running = true;
@@ -87,7 +97,7 @@ export function create_in_transition(node, fn, params) {
 	};
 }
 
-export function create_out_transition(node, fn, params, callback) {
+export function create_out_transition(node, fn, params) {
 	let config = fn(node, params);
 	let running = true;
 	let animation_name;
@@ -95,7 +105,6 @@ export function create_out_transition(node, fn, params, callback) {
 	const group = outros;
 
 	group.remaining += 1;
-	group.callbacks.push(callback); // TODO do we even need multiple callbacks? can we just have the one?
 
 	function go() {
 		if (typeof config === 'function') config = config();

src/internal/utils.js

@@ -16,13 +16,6 @@ export function isPromise(value) {
 	return value && typeof value.then === 'function';
 }
 
-export function callAfter(fn, i) {
-	if (i === 0) fn();
-	return () => {
-		if (!--i) fn();
-	};
-}
-
 export function addLoc(element, file, line, column, char) {
 	element.__svelte_meta = {
 		loc: { file, line, column, char }

test/runtime/samples/nested-transition-detach-if-false/_config.js

@@ -13,7 +13,7 @@ export default {
 		</li>
 	`,
 
-	test({ assert, component, target, window, raf }) {
+	test({ assert, component, target }) {
 		component.folder.open = false;
 		assert.htmlEqual(target.innerHTML, `
 			<li>