implement full-state computed properties - fixes #1303

Author: Rich-Harris

src/compile/Compiler.ts

@@ -564,16 +564,29 @@ export default class Compiler {
 				if (templateProperties.computed) {
 					const dependencies = new Map();
 
+					const fullStateComputations = [];
+
 					templateProperties.computed.value.properties.forEach((prop: Node) => {
 						const key = getName(prop.key);
 						const value = prop.value;
 
-						const deps = value.params[0].properties.map(prop => prop.key.name);
-
-						deps.forEach(dep => {
-							this.expectedProperties.add(dep);
+						addDeclaration(key, value, false, 'computed', {
+							state: true,
+							changed: true
 						});
-						dependencies.set(key, deps);
+
+						const param = value.params[0];
+
+						if (param.type === 'ObjectPattern') {
+							const deps = param.properties.map(prop => prop.key.name);
+
+							deps.forEach(dep => {
+								this.expectedProperties.add(dep);
+							});
+							dependencies.set(key, deps);
+						} else {
+							fullStateComputations.push({ key, deps: null })
+						}
 					});
 
 					const visited = new Set();
@@ -590,16 +603,15 @@ export default class Compiler {
 						computations.push({ key, deps });
 
 						const prop = templateProperties.computed.value.properties.find((prop: Node) => getName(prop.key) === key);
-
-						addDeclaration(key, prop.value, false, 'computed', {
-							state: true,
-							changed: true
-						});
 					};
 
 					templateProperties.computed.value.properties.forEach((prop: Node) =>
 						visit(getName(prop.key))
 					);
+
+					if (fullStateComputations.length > 0) {
+						computations.push(...fullStateComputations);
+					}
 				}
 
 				if (templateProperties.data) {

src/compile/dom/index.ts

@@ -64,10 +64,6 @@ export default function dom(
 
 	if (computations.length) {
 		computations.forEach(({ key, deps }) => {
-			deps.forEach(dep => {
-				computationDeps.add(dep);
-			});
-
 			if (target.readonly.has(key)) {
 				// <svelte:window> bindings
 				throw new Error(
@@ -77,11 +73,22 @@ export default function dom(
 
 			target.readonly.add(key);
 
-			const condition = `${deps.map(dep => `changed.${dep}`).join(' || ')}`;
+			if (deps) {
+				deps.forEach(dep => {
+					computationDeps.add(dep);
+				});
 
-			const statement = `if (this._differs(state.${key}, (state.${key} = %computed-${key}(state)))) changed.${key} = true;`;
+				const condition = `${deps.map(dep => `changed.${dep}`).join(' || ')}`;
+				const statement = `if (this._differs(state.${key}, (state.${key} = %computed-${key}(state)))) changed.${key} = true;`;
 
-			computationBuilder.addConditional(condition, statement);
+				computationBuilder.addConditional(condition, statement);
+			} else {
+				// computed property depends on entire state object —
+				// these must go at the end
+				computationBuilder.addLine(
+					`if (this._differs(state.${key}, (state.${key} = %computed-${key}(state)))) changed.${key} = true;`
+				);
+			}
 		});
 	}
 

src/compile/ssr/index.ts

@@ -120,8 +120,7 @@ export default function ssr(
 			ctx = Object.assign(${initialState.join(', ')});
 
 			${computations.map(
-				({ key, deps }) =>
-					`ctx.${key} = %computed-${key}(ctx);`
+				({ key }) => `ctx.${key} = %computed-${key}(ctx);`
 			)}
 
 			${target.bindings.length &&

src/validate/js/propValidators/computed.ts

@@ -81,14 +81,5 @@ export default function computed(validator: Validator, prop: Node) {
 				message: `Computed properties must take a single argument`
 			});
 		}
-
-		const param = params[0];
-		if (param.type !== 'ObjectPattern') {
-			// TODO post-v2, allow the entire object to be passed in
-			validator.error(computation.value, {
-				code: `invalid-computed-argument`,
-				message: `Computed property argument must be a destructured object pattern`
-			});
-		}
 	});
 }

test/runtime/samples/computed-state-object/_config.js

@@ -0,0 +1,21 @@
+export default {
+	data: { a: 1 },
+
+	html: `
+		<p>a: 1</p>
+		<p>x: 2</p>
+		<p>y: 4</p>
+		<p>z: 8</p>
+	`,
+
+	test(assert, component, target) {
+		component.set({ a: 2 });
+
+		assert.htmlEqual(target.innerHTML, `
+			<p>a: 2</p>
+			<p>x: 4</p>
+			<p>y: 8</p>
+			<p>z: 16</p>
+		`)
+	},
+};

test/runtime/samples/computed-state-object/main.html

@@ -0,0 +1,14 @@
+<p>a: {a}</p>
+<p>x: {x}</p>
+<p>y: {y}</p>
+<p>z: {z}</p>
+
+<script>
+	export default {
+		computed: {
+			y: state => state.x * 2,
+			z: state => state.y * 2,
+			x: ({ a }) => a * 2
+		}
+	};
+</script>