fix(string): preserve falsy variable values in template()

src/string.test.ts

@@ -94,6 +94,19 @@ it('namedTemplate', () => {
       k => String(+k * 2),
     ),
   ).toEqual('2 4 6 known key')
+
+  // Falsy values that are explicitly set should not fall back to the fallback
+  expect(
+    template('{count}', { count: 0 }, 'N/A'),
+  ).toEqual('0')
+
+  expect(
+    template('{active}', { active: false }, 'unknown'),
+  ).toEqual('false')
+
+  expect(
+    template('{name}', { name: '' }, 'anonymous'),
+  ).toEqual('')
 })
 
 it('slash', () => {

src/string.ts

@@ -67,7 +67,7 @@ export function template(str: string, ...args: any[]): string {
 
   if (isObject(firstArg)) {
     const vars = firstArg as Record<string, any>
-    return str.replace(/\{(\w+)\}/g, (_, key) => vars[key] || ((typeof fallback === 'function' ? fallback(key) : fallback) ?? key))
+    return str.replace(/\{(\w+)\}/g, (_, key) => key in vars ? vars[key] : ((typeof fallback === 'function' ? fallback(key) : fallback) ?? key))
   }
   else {
     return str.replace(/\{(\d+)\}/g, (_, key) => {