From 10548373d569966dbac1a1a052f2731a2c293c87 Mon Sep 17 00:00:00 2001
From: Rich Harris <richard.a.harris@gmail.com>
Date: Fri, 30 Aug 2019 12:02:20 -0400
Subject: [PATCH] dont generate code for non-updating if block - fixes #3447

---
 .../compile/render_dom/wrappers/IfBlock.ts    | 98 +++++++++----------
 test/js/samples/if-block-complex/expected.js  | 14 +--
 2 files changed, 50 insertions(+), 62 deletions(-)

diff --git a/src/compiler/compile/render_dom/wrappers/IfBlock.ts b/src/compiler/compile/render_dom/wrappers/IfBlock.ts
index fb364a5343..f12929ffb1 100644
--- a/src/compiler/compile/render_dom/wrappers/IfBlock.ts
+++ b/src/compiler/compile/render_dom/wrappers/IfBlock.ts
@@ -441,58 +441,58 @@ export default class IfBlockWrapper extends Wrapper {
 			`if (${name}) ${name}.m(${initial_mount_node}, ${anchor_node});`
 		);
 
-		const update_mount_node = this.get_update_mount_node(anchor);
-
-		const enter = dynamic
-			? deindent`
-				if (${name}) {
-					${name}.p(changed, ctx);
-					${has_transitions && `@transition_in(${name}, 1);`}
-				} else {
-					${name} = ${branch.block.name}(ctx);
-					${name}.c();
-					${has_transitions && `@transition_in(${name}, 1);`}
-					${name}.m(${update_mount_node}, ${anchor});
-				}
-			`
-			: deindent`
-				if (!${name}) {
-					${name} = ${branch.block.name}(ctx);
-					${name}.c();
-					${has_transitions && `@transition_in(${name}, 1);`}
-					${name}.m(${update_mount_node}, ${anchor});
-				${has_transitions && `} else {
-					@transition_in(${name}, 1);`}
-				}
-			`;
+		if (!branch.dependencies || branch.dependencies.length > 0) {
+			const update_mount_node = this.get_update_mount_node(anchor);
 
-		if (branch.snippet && branch.dependencies.length) {
-			block.builders.update.add_block(`if (${branch.dependencies.map(n => `changed.${n}`).join(' || ')}) ${branch.condition} = ${branch.snippet}`);
-		}
+			const enter = dynamic
+				? deindent`
+					if (${name}) {
+						${name}.p(changed, ctx);
+						${has_transitions && `@transition_in(${name}, 1);`}
+					} else {
+						${name} = ${branch.block.name}(ctx);
+						${name}.c();
+						${has_transitions && `@transition_in(${name}, 1);`}
+						${name}.m(${update_mount_node}, ${anchor});
+					}
+				`
+				: deindent`
+					if (!${name}) {
+						${name} = ${branch.block.name}(ctx);
+						${name}.c();
+						${has_transitions && `@transition_in(${name}, 1);`}
+						${name}.m(${update_mount_node}, ${anchor});
+					} ${has_transitions && `else @transition_in(${name}, 1);`}
+				`;
+
+			if (branch.snippet) {
+				block.builders.update.add_block(`if (${branch.dependencies.map(n => `changed.${n}`).join(' || ')}) ${branch.condition} = ${branch.snippet}`);
+			}
 
-		// no `p()` here — we don't want to update outroing nodes,
-		// as that will typically result in glitching
-		if (branch.block.has_outro_method) {
-			block.builders.update.add_block(deindent`
-				if (${branch.condition}) {
-					${enter}
-				} else if (${name}) {
-					@group_outros();
-					@transition_out(${name}, 1, 1, () => {
+			// no `p()` here — we don't want to update outroing nodes,
+			// as that will typically result in glitching
+			if (branch.block.has_outro_method) {
+				block.builders.update.add_block(deindent`
+					if (${branch.condition}) {
+						${enter}
+					} else if (${name}) {
+						@group_outros();
+						@transition_out(${name}, 1, 1, () => {
+							${name} = null;
+						});
+						@check_outros();
+					}
+				`);
+			} else {
+				block.builders.update.add_block(deindent`
+					if (${branch.condition}) {
+						${enter}
+					} else if (${name}) {
+						${name}.d(1);
 						${name} = null;
-					});
-					@check_outros();
-				}
-			`);
-		} else {
-			block.builders.update.add_block(deindent`
-				if (${branch.condition}) {
-					${enter}
-				} else if (${name}) {
-					${name}.d(1);
-					${name} = null;
-				}
-			`);
+					}
+				`);
+			}
 		}
 
 		block.builders.destroy.add_line(`${if_name}${name}.d(${detaching});`);
diff --git a/test/js/samples/if-block-complex/expected.js b/test/js/samples/if-block-complex/expected.js
index 8dffddef33..f0da492e3c 100644
--- a/test/js/samples/if-block-complex/expected.js
+++ b/test/js/samples/if-block-complex/expected.js
@@ -49,19 +49,7 @@ function create_fragment(ctx) {
 			insert(target, if_block_anchor, anchor);
 		},
 
-		p(changed, ctx) {
-			if (show_if) {
-				if (!if_block) {
-					if_block = create_if_block(ctx);
-					if_block.c();
-					if_block.m(if_block_anchor.parentNode, if_block_anchor);
-				}
-			} else if (if_block) {
-				if_block.d(1);
-				if_block = null;
-			}
-		},
-
+		p: noop,
 		i: noop,
 		o: noop,