implement bind:group for checkbox inputs (#312)

src/generators/Generator.js

@@ -22,6 +22,8 @@ export default class Generator {
 		this.components = {};
 		this.events = {};
 
+		this.bindingGroups = [];
+
 		// track which properties are needed, so we can provide useful info
 		// in dev mode
 		this.expectedProperties = {};

src/generators/dom/index.js

@@ -343,6 +343,10 @@ export default function dom ( parsed, source, options, names ) {
 		);
 	}
 
+	if ( generator.bindingGroups.length ) {
+		constructorBlock.addLine( `this._bindingGroups = [ ${Array( generator.bindingGroups.length ).fill( '[]' ).join( ', ' )} ];` );
+	}
+
 	constructorBlock.addBlock( deindent`
 		this._observers = {
 			pre: Object.create( null ),

src/generators/dom/visitors/Element.js

@@ -20,7 +20,8 @@ export default {
 			allUsedContexts: [],
 
 			init: new CodeBuilder(),
-			update: new CodeBuilder()
+			update: new CodeBuilder(),
+			teardown: new CodeBuilder()
 		};
 
 		const isToplevel = generator.current.localElementDepth === 0;
@@ -85,6 +86,7 @@ export default {
 
 		generator.current.builders.init.addBlock( local.init );
 		if ( !local.update.isEmpty() ) generator.current.builders.update.addBlock( local.update );
+		if ( !local.teardown.isEmpty() ) generator.current.builders.teardown.addBlock( local.teardown );
 
 		generator.createMountStatement( name );
 

src/generators/dom/visitors/attributes/addElementAttributes.js

@@ -2,6 +2,7 @@ import attributeLookup from './lookup.js';
 import addElementBinding from './addElementBinding';
 import deindent from '../../../../utils/deindent.js';
 import flattenReference from '../../../../utils/flattenReference.js';
+import getStaticAttributeValue from './binding/getStaticAttributeValue.js';
 
 export default function addElementAttributes ( generator, node, local ) {
 	node.attributes.forEach( attribute => {
@@ -13,8 +14,12 @@ export default function addElementAttributes ( generator, node, local ) {
 
 			let dynamic = false;
 
-			const isBoundOptionValue = node.name === 'option' && name === 'value'; // TODO check it's actually bound
-			const propertyName = isBoundOptionValue ? '__value' : metadata && metadata.propertyName;
+			const isIndirectlyBoundValue = name === 'value' && (
+				node.name === 'option' || // TODO check it's actually bound
+				node.name === 'input' && /^(checkbox|radio)$/.test( getStaticAttributeValue( node, 'type' ) )
+			);
+
+			const propertyName = isIndirectlyBoundValue ? '__value' : metadata && metadata.propertyName;
 
 			const isXlink = name.slice( 0, 6 ) === 'xlink:';
 
@@ -134,12 +139,11 @@ export default function addElementAttributes ( generator, node, local ) {
 				local.update.addLine( updater );
 			}
 
-			if ( isBoundOptionValue ) {
-				local.init.addLine( `${local.name}.value = ${local.name}.__value` );
+			if ( isIndirectlyBoundValue ) {
+				const updateValue = `${local.name}.value = ${local.name}.__value;`;
 
-				if (dynamic) {
-					local.update.addLine( `${local.name}.value = ${local.name}.__value` );
-				}
+				local.init.addLine( updateValue );
+				if ( dynamic ) local.update.addLine( updateValue );
 			}
 		}
 

src/generators/dom/visitors/attributes/addElementBinding.js

@@ -1,9 +1,10 @@
 import deindent from '../../../../utils/deindent.js';
 import flattenReference from '../../../../utils/flattenReference.js';
 import getSetter from './binding/getSetter.js';
+import getStaticAttributeValue from './binding/getStaticAttributeValue.js';
 
 export default function createBinding ( generator, node, attribute, current, local ) {
-	const { name } = flattenReference( attribute.value );
+	const { name, keypath } = flattenReference( attribute.value );
 	const { snippet, contexts, dependencies } = generator.contextualise( attribute.value );
 
 	if ( dependencies.length > 1 ) throw new Error( 'An unexpected situation arose. Please raise an issue at https://github.com/sveltejs/svelte/issues — thanks!' );
@@ -14,20 +15,20 @@ export default function createBinding ( generator, node, attribute, current, loc
 
 	const handler = current.getUniqueName( `${local.name}ChangeHandler` );
 
-	const isMultipleSelect = node.name === 'select' && node.attributes.find( attr => attr.name.toLowerCase() === 'multiple' ); // TODO ensure that this is a static attribute
-	const value = getBindingValue( local, node, attribute, isMultipleSelect );
+	const isMultipleSelect = node.name === 'select' && node.attributes.find( attr => attr.name.toLowerCase() === 'multiple' ); // TODO use getStaticAttributeValue
+	const bindingGroup = attribute.name === 'group' ? getBindingGroup( generator, current, attribute, keypath ) : null;
+	const value = getBindingValue( generator, local, node, attribute, isMultipleSelect, bindingGroup );
 	const eventName = getBindingEventName( node );
 
 	let setter = getSetter({ current, name, context: '__svelte', attribute, dependencies, snippet, value });
-
-	// special case
-	if ( node.name === 'select' && !isMultipleSelect ) {
-		setter = `var selectedOption = ${local.name}.selectedOptions[0] || ${local.name}.options[0];\n` + setter;
-	}
-
 	let updateElement;
 
+	// <select> special case
 	if ( node.name === 'select' ) {
+		if ( !isMultipleSelect ) {
+			setter = `var selectedOption = ${local.name}.selectedOptions[0] || ${local.name}.options[0];\n` + setter;
+		}
+
 		const value = generator.current.getUniqueName( 'value' );
 		const i = generator.current.getUniqueName( 'i' );
 		const option = generator.current.getUniqueName( 'option' );
@@ -49,7 +50,35 @@ export default function createBinding ( generator, node, attribute, current, loc
 				${ifStatement}
 			}
 		`;
-	} else {
+	}
+
+	// <input type='checkbox|radio' bind:group='selected'> special case
+	else if ( attribute.name === 'group' ) {
+		const type = getStaticAttributeValue( node, 'type' );
+
+		if ( type === 'checkbox' ) {
+			local.init.addLine(
+				`component._bindingGroups[${bindingGroup}].push( ${local.name} );`
+			);
+
+			local.teardown.addBlock(
+				`component._bindingGroups[${bindingGroup}].splice( component._bindingGroups[${bindingGroup}].indexOf( ${local.name} ), 1 );`
+			);
+
+			updateElement = `${local.name}.checked = ~${snippet}.indexOf( ${local.name}.__value );`;
+		}
+
+		else if ( type === 'radio' ) {
+			throw new Error( 'TODO' );
+		}
+
+		else {
+			throw new Error( `Unexpected bind:group` ); // TODO catch this in validation with a better error
+		}
+	}
+
+	// everything else
+	else {
 		updateElement = `${local.name}.${attribute.name} = ${snippet};`;
 	}
 
@@ -93,14 +122,34 @@ function getBindingEventName ( node ) {
 	return 'change';
 }
 
-function getBindingValue ( local, node, attribute, isMultipleSelect ) {
+function getBindingValue ( generator, local, node, attribute, isMultipleSelect, bindingGroup ) {
+	// <select multiple bind:value='selected>
 	if ( isMultipleSelect ) {
 		return `[].map.call( ${local.name}.selectedOptions, function ( option ) { return option.__value; })`;
 	}
 
+	// <select bind:value='selected>
 	if ( node.name === 'select' ) {
 		return 'selectedOption && selectedOption.__value';
 	}
 
+	// <input type='checkbox' bind:group='foo'>
+	if ( attribute.name === 'group' ) {
+		return `${generator.helper( 'getBindingGroupValue' )}( component._bindingGroups[${bindingGroup}] )`;
+	}
+
+	// everything else
 	return `${local.name}.${attribute.name}`;
+}
+
+function getBindingGroup ( generator, current, attribute, keypath ) {
+	// TODO handle contextual bindings — `keypath` should include unique ID of
+	// each block that provides context
+	let index = generator.bindingGroups.indexOf( keypath );
+	if ( index === -1 ) {
+		index = generator.bindingGroups.length;
+		generator.bindingGroups.push( keypath );
+	}
+
+	return index;
 }

src/generators/dom/visitors/attributes/binding/getStaticAttributeValue.js

@@ -0,0 +1,11 @@
+export default function getStaticAttributeValue ( node, name ) {
+	const attribute = node.attributes.find( attr => attr.name.toLowerCase() === name );
+	if ( !attribute ) return null;
+
+	if ( attribute.value.length !== 1 || attribute.value[0].type !== 'Text' ) {
+		// TODO catch this in validation phase, give a more useful error (with location etc)
+		throw new Error( `'${name} must be a static attribute` );
+	}
+
+	return attribute.value[0].data;
+}

src/shared/dom.js

@@ -53,3 +53,11 @@ export function setAttribute ( node, attribute, value ) {
 export function setXlinkAttribute ( node, attribute, value ) {
 	node.setAttributeNS( 'http://www.w3.org/1999/xlink', attribute, value );
 }
+
+export function getBindingGroupValue ( group ) {
+	var value = [];
+	for ( var i = 0; i < group.length; i += 1 ) {
+		if ( group[i].checked ) value.push( group[i].__value );
+	}
+	return value;
+}

test/generator/samples/binding-input-checkbox-group/_config.js

@@ -5,13 +5,13 @@ const values = [
 ];
 
 export default {
-	// solo: true,
-
 	data: {
 		values,
 		selected: [ values[1] ]
 	},
 
+	'skip-ssr': true, // values are rendered as [object Object]
+
 	html: `
 		<label>
 			<input type="checkbox"> Alpha
@@ -38,7 +38,7 @@ export default {
 		inputs[0].checked = true;
 		inputs[0].dispatchEvent( event );
 
-		assert.equal( target.innerHTML, `
+		assert.htmlEqual( target.innerHTML, `
 			<label>
 				<input type="checkbox"> Alpha
 			</label>
@@ -54,12 +54,12 @@ export default {
 			<p>Alpha, Beta</p>
 		` );
 
-		component.set({ selected: [ 'Beta', 'Gamma' ] });
+		component.set({ selected: [ values[1], values[2] ] });
 		assert.equal( inputs[0].checked, false );
 		assert.equal( inputs[1].checked, true );
 		assert.equal( inputs[2].checked, true );
 
-		assert.equal( target.innerHTML, `
+		assert.htmlEqual( target.innerHTML, `
 			<label>
 				<input type="checkbox"> Alpha
 			</label>

test/generator/samples/binding-input-checkbox-group/main.html

@@ -4,4 +4,4 @@
 	</label>
 {{/each}}
 
-<p>{{selected.map( function ( value ) { return value.name; }) }}</p>
+<p>{{selected.map( function ( value ) { return value.name; }).join( ', ' ) }}</p>