Better template variable extraction

package.json

@@ -1,6 +1,6 @@
 {
 	"name": "@ztimson/utils",
-	"version": "0.27.14",
+	"version": "0.28.1",
 	"description": "Utility library",
 	"author": "Zak Timson",
 	"license": "MIT",

src/index.ts

@@ -19,6 +19,7 @@ export * from './path-events';
 export * from './promise-progress';
 export * from './search';
 export * from './string';
+export * from './template';
 export * from './time';
 export * from './types';
 export * from 'var-persist';

src/path-events.ts

@@ -109,18 +109,16 @@ export class PathEvent {
 			return;
 		}
 
-		// Check cache first
 		if(PathEvent.pathEventCache.has(e)) {
 			Object.assign(this, PathEvent.pathEventCache.get(e)!);
 			return;
 		}
 
-		let [p, method] = e.replaceAll(/\/{2,}/g, '/').split(':');
+		let [p, method] = e.replaceAll(/(^|\/)\*+\/?$/g, '').split(':');
 		if(!method) method = '*';
 
 		// Handle special cases
 		if(p === '' || p === undefined || p === '*') {
-			// Empty string with methods (e.g., ":*") matches the root level/everything
 			this.module = '';
 			this.path = '';
 			this.fullPath = '**';
@@ -136,17 +134,74 @@ export class PathEvent {
 		this.path = temp.join('/');
 		this.fullPath = `${this.module}${this.module && this.path ? '/' : ''}${this.path}`;
 		this.name = temp.pop() || '';
-
-		// Don't trim /** - it's needed for glob matching to work properly
-		// Only trim if there's something after it which won't happen with our parsing
-
 		this.hasGlob = this.fullPath.includes('*');
 		this.methods = new ASet(<any>method.split(''));
-
-		// Store in cache
 		PathEvent.pathEventCache.set(e, this);
 	}
 
+	/**
+	 * Check if a filter pattern matches a target path
+	 * @private
+	 */
+	private static matches(pattern: PathEvent, target: PathEvent): boolean {
+		const methodsMatch = pattern.all || target.all || pattern.methods.intersection(target.methods).length > 0;
+		if(!methodsMatch) return false;
+		if(!pattern.hasGlob && !target.hasGlob) {
+			const last = pattern.fullPath[target.fullPath.length];
+			return pattern.fullPath.startsWith(target.fullPath) && (last == null || last == '/');
+		}
+		if(pattern.hasGlob) return this.pathMatchesGlob(target.fullPath, pattern.fullPath);
+		return this.pathMatchesGlob(pattern.fullPath, target.fullPath);
+	}
+
+	/**
+	 * Check if a path matches a glob pattern
+	 * @private
+	 */
+	private static pathMatchesGlob(path: string, pattern: string): boolean {
+		if(pattern === path) return true;
+		const pathParts = path.split('/').filter(p => !!p);
+		const patternParts = pattern.split('/').filter(p => !!p);
+
+		let pathIdx = 0;
+		let patternIdx = 0;
+		while (patternIdx < patternParts.length && pathIdx < pathParts.length) {
+			const patternPart = patternParts[patternIdx];
+			if(patternPart === '**') {
+				if(patternIdx === patternParts.length - 1) return true;
+				while (pathIdx < pathParts.length) {
+					if(PathEvent.pathMatchesGlob(pathParts.slice(pathIdx).join('/'), patternParts.slice(patternIdx + 1).join('/'))) return true;
+					pathIdx++;
+				}
+				return false;
+			} else if(patternPart === '*') {
+				pathIdx++;
+				patternIdx++;
+			} else {
+				if(patternPart !== pathParts[pathIdx]) return false;
+				pathIdx++;
+				patternIdx++;
+			}
+		}
+		if(patternIdx < patternParts.length) return patternParts.slice(patternIdx).every(p => p === '**');
+		return pathIdx === pathParts.length;
+	}
+
+	/**
+	 * Score a path for specificity ranking (lower = more specific = higher priority)
+	 * @private
+	 */
+	private static scoreSpecificity(path: string): number {
+		if(path === '**' || path === '') return Number.MAX_SAFE_INTEGER;
+		const segments = path.split('/').filter(p => !!p);
+		let score = -segments.length;
+		segments.forEach(seg => {
+			if(seg === '**') score += 0.5;
+			else if(seg === '*') score += 0.25;
+		});
+		return score;
+	}
+
 	/** Clear the cache of all PathEvents */
 	static clearCache(): void {
 		PathEvent.pathEventCache.clear();
@@ -157,82 +212,6 @@ export class PathEvent {
 		PathEvent.permissionCache.clear();
 	}
 
-	/**
-	 * Score a path for specificity ranking (lower = more specific = higher priority)
-	 * @private
-	 */
-	private static scoreSpecificity(path: string): number {
-		if(path === '**' || path === '') return Number.MAX_SAFE_INTEGER; // Least specific
-
-		const segments = path.split('/').filter(p => !!p);
-		// Base score: number of segments (more segments = more specific = lower score)
-		let score = -segments.length;
-
-		// Penalty for wildcards (makes them less specific than exact matches)
-		// ADD to score to make it HIGHER/WORSE
-		segments.forEach(seg => {
-			if(seg === '**') score += 0.5;
-			else if(seg === '*') score += 0.25;
-		});
-
-		return score;
-	}
-
-	/**
-	 * Check if a path matches a glob pattern
-	 * @private
-	 */
-	private static pathMatchesGlob(path: string, pattern: string): boolean {
-		// Handle exact match
-		if(pattern === path) return true;
-
-		const pathParts = path.split('/').filter(p => !!p);
-		const patternParts = pattern.split('/').filter(p => !!p);
-
-		let pathIdx = 0;
-		let patternIdx = 0;
-
-		while (patternIdx < patternParts.length && pathIdx < pathParts.length) {
-			const patternPart = patternParts[patternIdx];
-
-			if(patternPart === '**') {
-				// ** matches zero or more path segments
-				if(patternIdx === patternParts.length - 1) {
-					// ** at the end matches everything
-					return true;
-				}
-				// Try matching from next pattern part onwards
-				const nextPattern = patternParts[patternIdx + 1];
-				while (pathIdx < pathParts.length) {
-					if(PathEvent.pathMatchesGlob(pathParts.slice(pathIdx).join('/'), patternParts.slice(patternIdx + 1).join('/'))) {
-						return true;
-					}
-					pathIdx++;
-				}
-				return false;
-			} else if(patternPart === '*') {
-				// * matches exactly one segment
-				pathIdx++;
-				patternIdx++;
-			} else {
-				// Exact match required
-				if(patternPart !== pathParts[pathIdx]) {
-					return false;
-				}
-				pathIdx++;
-				patternIdx++;
-			}
-		}
-
-		// Check if we've consumed all pattern parts
-		if(patternIdx < patternParts.length) {
-			// Remaining pattern parts must all be ** to match
-			return patternParts.slice(patternIdx).every(p => p === '**');
-		}
-
-		return pathIdx === pathParts.length;
-	}
-
 	/**
 	 * Combine multiple events into one parsed object. Longest path takes precedent, but all subsequent methods are
 	 * combined until a "none" is reached
@@ -242,32 +221,22 @@ export class PathEvent {
 	 */
 	static combine(...paths: (string | PathEvent)[]): PathEvent {
 		const parsed = paths.map(p => p instanceof PathEvent ? p : new PathEvent(p));
-
-		// Sort by specificity: lower score = more specific = higher priority
 		const sorted = parsed.toSorted((p1, p2) => {
 			const score1 = PathEvent.scoreSpecificity(p1.fullPath);
 			const score2 = PathEvent.scoreSpecificity(p2.fullPath);
 			return score1 - score2;
 		});
-
 		let result: PathEvent | null = null;
-
 		for (const p of sorted) {
 			if(!result) {
 				result = p;
 			} else {
-				// Only combine if current result's path starts with or matches the new permission's path
 				if(result.fullPath.startsWith(p.fullPath)) {
-					// If we hit a none at a parent level, stop here
-					if(p.none) {
-						break;
-					}
-					// Combine methods for permissions in the same hierarchy
+					if(p.none) break;
 					result.methods = new ASet([...result.methods, ...p.methods]);
 				}
 			}
 		}
-
 		return result || new PathEvent('');
 	}
 
@@ -284,35 +253,6 @@ export class PathEvent {
 		return parsedTarget.filter(t => !!parsedFilter.find(r => PathEvent.matches(r, t)));
 	}
 
-	/**
-	 * Check if a filter pattern matches a target path
-	 * @private
-	 */
-	private static matches(pattern: PathEvent, target: PathEvent): boolean {
-		// Handle special cases
-		if(pattern.fullPath === '' || target.fullPath === '') return false;
-		if(pattern.fullPath === '**') return pattern.methods.has('*') || pattern.methods.intersection(target.methods).length > 0;
-		if(target.fullPath === '**') return pattern.methods.has('*') || target.methods.has('*') || pattern.methods.intersection(target.methods).length > 0;
-
-		// Check methods
-		const methodsMatch = pattern.all || target.all || pattern.methods.intersection(target.methods).length > 0;
-		if(!methodsMatch) return false;
-
-		// Check paths
-		if(!pattern.hasGlob && !target.hasGlob) {
-			// Fast path: no globs, use string comparison
-			return pattern.fullPath === target.fullPath;
-		}
-
-		if(pattern.hasGlob) {
-			// Pattern has glob, match target against it
-			return this.pathMatchesGlob(target.fullPath, pattern.fullPath);
-		}
-
-		// Target has glob but pattern doesn't - pattern must match within target's glob range
-		return this.pathMatchesGlob(pattern.fullPath, target.fullPath);
-	}
-
 	/**
 	 * Squash 2 sets of paths & return true if any overlap is found
 	 *
@@ -323,8 +263,6 @@ export class PathEvent {
 	static has(target: string | PathEvent | (string | PathEvent)[], ...has: (string | PathEvent)[]): boolean {
 		const parsedTarget = makeArray(target).map(pe => pe instanceof PathEvent ? pe : new PathEvent(pe));
 		const parsedRequired = makeArray(has).map(pe => pe instanceof PathEvent ? pe : new PathEvent(pe));
-
-		// Check if any target permission matches any required permission
 		return !!parsedRequired.find(r => !!parsedTarget.find(t => PathEvent.matches(r, t)));
 	}
 

src/template.ts

@@ -0,0 +1,157 @@
+import {BadRequestError} from './errors.ts';
+import {dotNotation} from './objects.ts';
+import {matchAll} from './string.ts';
+import {formatDate} from './time.ts';
+
+export class TemplateError extends BadRequestError { }
+
+export function findTemplateVars(html: string): Record<string, any> {
+	const variables = new Set<string>();
+	const excluded = new Set<string>(['true', 'false', 'null', 'undefined']);
+
+	// Extract & exclude loop variables
+	for (const loop of matchAll(html, /\{\{\s*?\*\s*?(.+?)\s+in\s+(.+?)\s*?}}/g)) {
+		const [element, index = 'index'] = loop[1].replaceAll(/[()\s]/g, '').split(',');
+		excluded.add(element);
+		excluded.add(index);
+		// Add the array reference (but exclude if it's a loop variable)
+		const arrayRef = loop[2].trim();
+		const arrayVar = arrayRef.split('.')[0].match(/^[a-zA-Z_$][a-zA-Z0-9_$]*/)?.[0];
+		if (arrayVar && !excluded.has(arrayVar)) variables.add(arrayVar);
+	}
+
+	// Extract variables from if/else-if conditions
+	for (const ifStmt of matchAll(html, /\{\{\s*?[!]?\?\s*?([^}]+?)\s*?}}/g)) {
+		const code = ifStmt[1].replace(/["'`][^"'`]*["'`]/g, ''); // Remove string literals
+		const vars = code.match(/[a-zA-Z_$][a-zA-Z0-9_$.]+/g) || [];
+		for (const v of vars) {
+			const root = v.split('.')[0];
+			if (!excluded.has(root)) variables.add(root);
+		}
+	}
+
+	// Extract variables from content within if blocks
+	for (const ifBlock of matchAll(html, /\{\{\s*?\?\s*?.+?\s*?}}([\s\S]*?)\{\{\s*?\/\?\s*?}}/g)) {
+		const content = ifBlock[1];
+		const regex = /\{\{\s*([^<>\*\?!/}\s][^}]*?)\s*}}/g;
+		let match;
+		while ((match = regex.exec(content)) !== null) {
+			const code = match[1].trim().replace(/["'`][^"'`]*["'`]/g, '');
+			const vars = code.match(/[a-zA-Z_$][a-zA-Z0-9_$.]+/g) || [];
+			for (const v of vars) {
+				const root = v.split('.')[0];
+				if (!excluded.has(root)) variables.add(v);
+			}
+		}
+	}
+
+	// Extract variables from regular interpolations
+	const regex = /\{\{\s*([^<>\*\?!/}\s][^}]*?)\s*}}/g;
+	let match;
+	while ((match = regex.exec(html)) !== null) {
+		const code = match[1].trim().replace(/["'`][^"'`]*["'`]/g, '');
+		const vars = code.match(/[a-zA-Z_$][a-zA-Z0-9_$.]+/g) || [];
+		for (const v of vars) {
+			const root = v.split('.')[0];
+			if (!excluded.has(root)) variables.add(v);
+		}
+	}
+
+	const result: Record<string, any> = {};
+	for (const path of variables) {
+		const parts = path.split('.');
+		let current = result;
+		for (let i = 0; i < parts.length; i++) {
+			const part = parts[i];
+			if (i === parts.length - 1) {
+				current[part] = '';
+			} else {
+				current[part] = current[part] || {};
+				current = current[part];
+			}
+		}
+	}
+	return result;
+}
+
+export async function renderTemplate(template: string, data: any, fetch?: (file: string) => Promise<string>) {
+	let content = template, found: any;
+	const now = new Date(), d = {
+		date: {
+			day: now.getDate(),
+			month: now.toLocaleString('default', { month: 'long' }),
+			year: now.getFullYear(),
+			time: now.toLocaleTimeString(),
+			format: formatDate
+		},
+		...(data || {}),
+	};
+	if(!fetch) fetch = (file) => { throw new TemplateError(`Unable to fetch template: ${file}`); }
+	const evaluate = (code: string, data: object, fatal = true) => {
+		try {
+			return Function('data', `with(data) { return ${code}; }`)(data);
+		} catch {
+			if(fatal) throw new TemplateError(`Failed to evaluate: ${code}`);
+			else return false;
+		}
+	}
+
+	// If Statements - Optimize what we render: `{{ ? javascript }} IF TRUE CONTENT {{ !? javascript }} ELSE-IF CONTENT {{ !? }} ELSE FALSE CONTENT {{ /? }}`
+	while(!!(found = /\{\{\s*?\?\s*?(.+?)\s*?}}([\s\S]*?)\{\{\s*?\/\?\s*?}}/g.exec(content))) {
+		const nested = matchAll(found[0], /\{\{\s*?\?.+?}}/g).slice(-1)?.[0]?.index;
+		if(nested != 0) found = /\{\{\s*?\?\s*?(.+?)\s*?}}([\s\S]*?)\{\{\s*?\/\?\s*?}}/g.exec(content.slice(found.index + nested))
+		const parts = found[2].split(/\{\{\s*?!\?\s*?/);
+		let result = evaluate(found[1], d, false) ? parts[0] : '';
+		if (!result) {
+			for (let i = 1; i < parts.length; i++) {
+				const [cond, body] = parts[i].split(/}}/);
+				if (!cond.trim()) {
+					result = body || '';
+					break;
+				}
+				if (evaluate(cond, d, false)) {
+					result = body || '';
+					break;
+				}
+			}
+		}
+		content = content.replace(found[0], result);
+	}
+
+	// Imports - We render bottom up: `{{ < file.html }}`
+	while(!!(found = /\{\{\s*?<\s*?(.+?)\s*?}}/g.exec(content))) {
+		const t = await fetch(found[1].trim());
+		if(!t) throw new TemplateError(`Unknown imported template: ${found[1].trim()}`);
+		content = content.replace(found[0], await renderTemplate(t, d, fetch));
+	}
+
+	// For Loops: `{{ * (row, index) in invoice }} CONTENT {{ /* }}`
+	while(!!(found = /\{\{\s*?\*\s*?(.+?)\s+in\s+(.+?)\s*?}}([\s\S]*?)\{\{\s*?\/\*\s*?}}/g.exec(content))) {
+		const split = found[1].replaceAll(/[()\s]/g, '').split(',');
+		const element = split[0];
+		const index = split[1] || 'index';
+		const array: any[] = <any>dotNotation(d, found[2]);
+		if(!array || typeof array != 'object') throw new TemplateError(`Cannot iterate: ${found[2]}`);
+		let compiled = [];
+		for(let i = 0; i < array.length; i++)
+			compiled.push(await renderTemplate(found[3], {...d, [element]: array[i], [index]: i}, fetch));
+		content = content.replace(found[0], compiled.join('\n'));
+	}
+
+	// Evaluate whatever is left - Should come last: `{{ javascript }}`
+	while(!!(found = /\{\{\s*([^<>\*\?!/}\s][^}]*?)\s*}}/g.exec(content))) {
+		content = content.replace(found[0], evaluate(found[1].trim(), d) ?? '');
+	}
+
+	// Extends: `{{ > file.html:property }} CONTENT {{ /> }}`
+	while(!!(found = /\{\{\s*?>\s*?(.+?):(.+?)\s*?}}([\s\S]*?)\{\{\s*?\/>\s*?}}/g.exec(content))) {
+		const t = await fetch(found[1].trim());
+		if(!t) throw new TemplateError(`Unknown extended templated: ${found[1].trim()}`);
+		content = content.replace(found[0], await renderTemplate(t, {
+			...d,
+			[found[2].trim()]: found[3],
+		}, fetch));
+	}
+
+	return content;
+}

tests/path-events.spec.ts

@@ -60,6 +60,10 @@ describe('Path Events', () => {
 			expect(pe.none).toBe(false);
 		});
 
+		it('Test several wild card perms', () => {
+			expect(PathEvent.has(['actions:*', 'groups:*', 'users:*'], 'groups/AUTH:r')).toBe(true);
+		});
+
 		it('setters for methods', () => {
 			const pe = new PathEvent('users/system:r');
 			pe.create = true;

tests/templates.spec.ts

@@ -0,0 +1,215 @@
+import {findTemplateVars, renderTemplate, TemplateError} from '../src';
+
+describe('findTemplateVars', () => {
+	test('extracts simple variables', () => {
+		const result = findTemplateVars('Hello {{ name }}!');
+		expect(result).toEqual({ name: '' });
+	});
+
+	test('extracts nested object paths', () => {
+		const result = findTemplateVars('{{ user.name }} is {{ user.age }}');
+		expect(result).toEqual({ user: { name: '', age: '' } });
+	});
+
+	test('extracts variables from if statements', () => {
+		const result = findTemplateVars('{{ ? active }}{{ message }}{{ /? }}');
+		expect(result).toEqual({ active: '', message: '' });
+	});
+
+	test('extracts variables from else-if conditions', () => {
+		const result = findTemplateVars('{{ ? status == "paid" }}PAID{{ !? status == "pending" }}{{ value }}{{ /? }}');
+		expect(result).toEqual({ status: '', value: '' });
+	});
+
+	test('extracts array reference from loops', () => {
+		const result = findTemplateVars('{{ * item in items }}{{ item }}{{ /* }}');
+		expect(result).toEqual({ items: '' });
+	});
+
+	test('excludes loop element variable', () => {
+		const result = findTemplateVars('{{ * item in items }}{{ item.name }}{{ /* }}');
+		expect(result).toEqual({ items: '' });
+		expect(result).not.toHaveProperty('item');
+	});
+
+	test('excludes loop index variable', () => {
+		const result = findTemplateVars('{{ * (item, i) in items }}{{ i }}:{{ item }}{{ /* }}');
+		expect(result).toEqual({ items: '' });
+		expect(result).not.toHaveProperty('item');
+		expect(result).not.toHaveProperty('i');
+	});
+
+	test('extracts external vars used inside loops', () => {
+		const result = findTemplateVars('{{ * item in items }}{{ item }}-{{ prefix }}{{ /* }}');
+		expect(result).toEqual({ items: '', prefix: '' });
+	});
+
+	test('handles nested loops', () => {
+		const result = findTemplateVars('{{ * row in rows }}{{ * col in row.cols }}{{ col }}{{ /* }}{{ /* }}');
+		expect(result).toEqual({ rows: '' });
+		expect(result).not.toHaveProperty('row');
+		expect(result).not.toHaveProperty('col');
+	});
+
+	test('extracts from complex nested template', () => {
+		const tpl = `
+{{ ? items.length > 0 }}
+{{ * (item, i) in items }}
+{{ i }}. {{ item.name }}: {{ currency }}{{ item.price }}
+{{ /* }}
+Total: {{ total }}
+{{ !? }}
+{{ emptyMessage }}
+{{ /? }}`;
+		const result = findTemplateVars(tpl);
+		expect(result).toEqual({
+			items: '',
+			currency: '',
+			total: '',
+			emptyMessage: ''
+		});
+		expect(result).not.toHaveProperty('item');
+		expect(result).not.toHaveProperty('i');
+	});
+
+	test('ignores template control syntax', () => {
+		const result = findTemplateVars('{{ < header.html }}{{ > layout.html:content }}content{{ /> }}');
+		expect(result).toEqual({});
+	});
+
+	test('handles multiple variables in expressions', () => {
+		const result = findTemplateVars('{{ firstName + " " + lastName }}');
+		expect(result).toEqual({ firstName: '', lastName: '' });
+	});
+});
+
+describe('renderTemplate', () => {
+	test('basic variable interpolation', async () => {
+		const result = await renderTemplate('Hello {{ name }}!', { name: 'World' });
+		expect(result).toBe('Hello World!');
+	});
+
+	test('nested object access', async () => {
+		const result = await renderTemplate('{{ user.name }} is {{ user.age }}', {
+			user: { name: 'Alice', age: 25 }
+		});
+		expect(result).toBe('Alice is 25');
+	});
+
+	test('method calls', async () => {
+		const result = await renderTemplate('{{ price.toFixed(2) }}', { price: 9.5 });
+		expect(result).toBe('9.50');
+	});
+
+	test('if statement true', async () => {
+		const result = await renderTemplate('{{ ? active }}YES{{ /? }}', { active: true });
+		expect(result).toBe('YES');
+	});
+
+	test('if statement false', async () => {
+		const result = await renderTemplate('{{ ? active }}YES{{ /? }}', { active: false });
+		expect(result).toBe('');
+	});
+
+	test('if-else', async () => {
+		const result = await renderTemplate('{{ ? active }}YES{{ !? }}NO{{ /? }}', { active: false });
+		expect(result).toBe('NO');
+	});
+
+	test('if-elseif-else', async () => {
+		const tpl = '{{ ? status == "paid" }}PAID{{ !? status == "pending" }}PENDING{{ !? }}OTHER{{ /? }}';
+		expect(await renderTemplate(tpl, { status: 'paid' })).toBe('PAID');
+		expect(await renderTemplate(tpl, { status: 'pending' })).toBe('PENDING');
+		expect(await renderTemplate(tpl, { status: 'failed' })).toBe('OTHER');
+	});
+
+	test('nested if statements', async () => {
+		const tpl = '{{ ? a }}A{{ ? b }}B{{ /? }}{{ /? }}';
+		expect(await renderTemplate(tpl, { a: true, b: true })).toBe('AB');
+		expect(await renderTemplate(tpl, { a: true, b: false })).toBe('A');
+		expect(await renderTemplate(tpl, { a: false, b: true })).toBe('');
+	});
+
+	test('for loop', async () => {
+		const tpl = '{{ * item in items }}{{ item }}{{ /* }}';
+		const result = await renderTemplate(tpl, { items: ['a', 'b', 'c'] });
+		expect(result).toBe('a\nb\nc');
+	});
+
+	test('for loop with index', async () => {
+		const tpl = '{{ * (item, i) in items }}{{ i }}:{{ item }}{{ /* }}';
+		const result = await renderTemplate(tpl, { items: ['a', 'b'] });
+		expect(result).toBe('0:a\n1:b');
+	});
+
+	test('for loop with objects', async () => {
+		const tpl = '{{ * user in users }}{{ user.name }}{{ /* }}';
+		const result = await renderTemplate(tpl, {
+			users: [{ name: 'Alice' }, { name: 'Bob' }]
+		});
+		expect(result).toBe('Alice\nBob');
+	});
+
+	test('for loop error on non-array', async () => {
+		await expect(
+			renderTemplate('{{ * x in notArray }}{{ x }}{{ /* }}', { notArray: 'string' })
+		).rejects.toThrow(TemplateError);
+	});
+
+	test('import template', async () => {
+		const fetch = async (file: string) => {
+			if (file === 'header.html') return 'HEADER: {{ title }}';
+			throw new Error('Not found');
+		};
+		const result = await renderTemplate('{{ < header.html }}', { title: 'Test' }, fetch);
+		expect(result).toBe('HEADER: Test');
+	});
+
+	test('import template error', async () => {
+		await expect(
+			renderTemplate('{{ < missing.html }}', {})
+		).rejects.toThrow(TemplateError);
+	});
+
+	test('extend template', async () => {
+		const fetch = async (file: string) => {
+			if (file === 'layout.html') return '<div>{{ content }}</div>';
+			throw new Error('Not found');
+		};
+		const result = await renderTemplate('{{ > layout.html:content }}Hello{{ /> }}', {}, fetch);
+		expect(result).toBe('<div>Hello</div>');
+	});
+
+	test('date object', async () => {
+		const result = await renderTemplate('{{ date.year }}', {});
+		expect(result).toBe(new Date().getFullYear().toString());
+	});
+
+	test('evaluation error', async () => {
+		await expect(
+			renderTemplate('{{ undefined.property }}', {})
+		).rejects.toThrow(TemplateError);
+	});
+
+	test('complex nested example', async () => {
+		const tpl = `
+{{ ? items.length > 0 }}
+{{ * (item, i) in items }}
+{{ i + 1 }}. {{ item.name }}: \${{ item.price.toFixed(2) }}
+{{ /* }}
+Total: \${{ total.toFixed(2) }}
+{{ !? }}
+No items
+{{ /? }}`;
+		const result = await renderTemplate(tpl, {
+			items: [
+				{ name: 'A', price: 10 },
+				{ name: 'B', price: 20 }
+			],
+			total: 30
+		});
+		expect(result.trim()).toContain('1. A: $10.00');
+		expect(result.trim()).toContain('2. B: $20.00');
+		expect(result.trim()).toContain('Total: $30.00');
+	});
+});