validate props, auto-generate props if unspecified

src/generators/Generator.ts

@@ -577,8 +577,8 @@ export default class Generator {
 			}
 
 			if (templateProperties.props) {
-				// TODO
-				this.props = templateProperties.props.value;
+				this.props = templateProperties.props.value.elements.map((element: Node) => element.value);
+				removeObjectKey(this.code, defaultExport.declaration, 'props');
 			}
 
 			// now that we've analysed the default export, we can determine whether or not we need to keep it

src/generators/dom/index.ts

@@ -232,12 +232,32 @@ export default function dom(
 	`;
 
 	if (generator.customElement) {
+		const props = generator.props || Array.from(generator.expectedProperties);
+
 		builder.addBlock(deindent`
 			class ${name} extends HTMLElement {
 				constructor(options = {}) {
 					super();
 					${constructorBody}
 				}
+
+				static get observedAttributes() {
+					return ${JSON.stringify(props)};
+				}
+
+				${props.map(prop => deindent`
+					get ${prop}() {
+						return this.get('${prop}');
+					}
+
+					set ${prop}(value) {
+						this.set({ ${prop}: value });
+					}
+				`).join('\n\n')}
+
+				attributeChangedCallback ( attr, oldValue, newValue ) {
+					this.set({ [attr]: newValue });
+				}
 			}
 
 			customElements.define('${generator.tag}', ${name});

src/validate/js/propValidators/index.ts

@@ -9,6 +9,7 @@ import methods from './methods';
 import components from './components';
 import events from './events';
 import namespace from './namespace';
+import props from './props';
 import tag from './tag';
 import transitions from './transitions';
 import setup from './setup';
@@ -25,6 +26,7 @@ export default {
 	components,
 	events,
 	namespace,
+	props,
 	tag,
 	transitions,
 	setup,

src/validate/js/propValidators/props.ts

@@ -0,0 +1,20 @@
+import { Validator } from '../../';
+import { Node } from '../../../interfaces';
+
+export default function props(validator: Validator, prop: Node) {
+	if (prop.value.type !== 'ArrayExpression') {
+		validator.error(
+			`'props' must be an array expression, if specified`,
+			prop.value.start
+		);
+	}
+
+	prop.value.elements.forEach((element: Node) => {
+		if (element.type !== 'Literal' || typeof element.value !== 'string') {
+			validator.error(
+				`'props' must be an array of string literals`,
+				element.start
+			);
+		}
+	});
+}

src/validate/js/propValidators/tag.ts

@@ -1,4 +1,3 @@
-import usesThisOrArguments from '../utils/usesThisOrArguments';
 import { Validator } from '../../';
 import { Node } from '../../../interfaces';