recalculate each block values lazily - fixes #1286

src/compile/nodes/EachBlock.ts

@@ -443,9 +443,9 @@ export default class EachBlock extends Node {
 				`;
 
 			block.builders.update.addBlock(deindent`
-				var ${each_block_value} = ${snippet};
-
 				if (${condition}) {
+					${each_block_value} = ${snippet};
+
 					for (var #i = ${start}; #i < ${each_block_value}.${length}; #i += 1) {
 						var ${this.each_context} = @assign(@assign({}, ctx), {
 							${this.contextProps.join(',\n')}

test/js/samples/deconflict-builtins/expected-bundle.js

@@ -186,9 +186,9 @@ function create_main_fragment(component, ctx) {
 		},
 
 		p: function update(changed, ctx) {
-			var each_value = ctx.createElement;
-
 			if (changed.createElement) {
+				each_value = ctx.createElement;
+
 				for (var i = 0; i < each_value.length; i += 1) {
 					var each_context = assign(assign({}, ctx), {
 						each_value: each_value,

test/js/samples/deconflict-builtins/expected.js

@@ -34,9 +34,9 @@ function create_main_fragment(component, ctx) {
 		},
 
 		p: function update(changed, ctx) {
-			var each_value = ctx.createElement;
-
 			if (changed.createElement) {
+				each_value = ctx.createElement;
+
 				for (var i = 0; i < each_value.length; i += 1) {
 					var each_context = assign(assign({}, ctx), {
 						each_value: each_value,

test/js/samples/each-block-changed-check/expected-bundle.js

@@ -192,9 +192,9 @@ function create_main_fragment(component, ctx) {
 		},
 
 		p: function update(changed, ctx) {
-			var each_value = ctx.comments;
-
 			if (changed.comments || changed.elapsed || changed.time) {
+				each_value = ctx.comments;
+
 				for (var i = 0; i < each_value.length; i += 1) {
 					var each_context = assign(assign({}, ctx), {
 						each_value: each_value,

test/js/samples/each-block-changed-check/expected.js

@@ -38,9 +38,9 @@ function create_main_fragment(component, ctx) {
 		},
 
 		p: function update(changed, ctx) {
-			var each_value = ctx.comments;
-
 			if (changed.comments || changed.elapsed || changed.time) {
+				each_value = ctx.comments;
+
 				for (var i = 0; i < each_value.length; i += 1) {
 					var each_context = assign(assign({}, ctx), {
 						each_value: each_value,