allow dynamic each-block to have static else-block

src/generators/dom/visitors/EachBlock.js

@@ -57,16 +57,28 @@ export default function visitEachBlock ( generator, block, state, node ) {
 			}
 		` );
 
-		block.builders.update.addBlock( deindent`
+		if ( node.else.hasUpdateMethod ) {
-			if ( !${each_block_value}.length && ${each_block_else} ) {
+			block.builders.update.addBlock( deindent`
-				${each_block_else}.update( changed, ${params} );
+				if ( !${each_block_value}.length && ${each_block_else} ) {
-			} else if ( !${each_block_value}.length ) {
+					${each_block_else}.update( changed, ${params} );
-				${each_block_else} = ${node.else._block.name}( ${params}, ${block.component} );
+				} else if ( !${each_block_value}.length ) {
-				${each_block_else}.mount( ${anchor}.parentNode, ${anchor} );
+					${each_block_else} = ${node.else._block.name}( ${params}, ${block.component} );
-			} else if ( ${each_block_else} ) {
+					${each_block_else}.mount( ${anchor}.parentNode, ${anchor} );
-				${each_block_else}.destroy( true );
+				} else if ( ${each_block_else} ) {
-			}
+					${each_block_else}.destroy( true );
-		` );
+				}
+			` );
+		} else {
+			block.builders.update.addBlock( deindent`
+				if ( ${each_block_value}.length ) {
+					if ( ${each_block_else} ) ${each_block_else}.destroy( true );
+				} else if ( !${each_block_else} ) {
+					${each_block_else} = ${node.else._block.name}( ${params}, ${block.component} );
+					${each_block_else}.mount( ${anchor}.parentNode, ${anchor} );
+				}
+			` );
+		}
+
 
 		block.builders.destroy.addBlock( deindent`
 			if ( ${each_block_else} ) {

test/runtime/samples/each-block-dynamic-else-static/_config.js

@@ -0,0 +1,29 @@
+export default {
+	solo: true,
+
+	data: {
+		animals: [ 'alpaca', 'baboon', 'capybara' ]
+	},
+
+	html: `
+		<p>alpaca</p>
+		<p>baboon</p>
+		<p>capybara</p>
+	`,
+
+	test ( assert, component, target ) {
+		component.set({ animals: [] });
+		assert.htmlEqual( target.innerHTML, `
+			<p>no animals</p>
+		` );
+
+		// trigger an 'update' of the else block, to ensure that
+		// non-existent update method is not called
+		component.set({ animals: [] });
+
+		component.set({ animals: ['wombat'] });
+		assert.htmlEqual( target.innerHTML, `
+			<p>wombat</p>
+		` );
+	}
+};

test/runtime/samples/each-block-dynamic-else-static/main.html

@@ -0,0 +1,5 @@
+{{#each animals as animal}}
+	<p>{{animal}}</p>
+{{else}}
+	<p>no animals</p>
+{{/each}}