feat: implement dateTime namespace (fixes #143)

src/evaluator/functions.ts

@@ -2,6 +2,7 @@ import type {ExprNode} from '../nodeTypes'
 import {
   DateTime,
   FALSE_VALUE,
+  fromDateTime,
   fromJS,
   fromNumber,
   fromPath,
@@ -645,6 +646,12 @@ math.avg = async function (args, scope, execute) {
 }
 math.avg.arity = 1
 
+const dateTime: FunctionSet = {}
+dateTime.now = async function now(args, scope, execute) {
+  return fromDateTime(new DateTime(scope.context.timestamp))
+}
+dateTime.now.arity = 0
+
 export const namespaces: NamespaceSet = {
   global: _global,
   string,
@@ -654,4 +661,5 @@ export const namespaces: NamespaceSet = {
   diff,
   sanity,
   math,
+  dateTime,
 }

test/functions.test.ts

@@ -31,6 +31,25 @@ t.test('Functions', async (t) => {
     })
   })
 
+  t.test('dateTime::now()', async (t) => {
+    t.test('returns the same value as dateTime(now())', async (t) => {
+      const query = `{"a": dateTime(now()), "b": dateTime::now()}`
+      const tree = parse(query)
+      const value = await evaluate(tree)
+      const data = await value.get()
+      t.same(data.a, data.b)
+    })
+
+    t.test('is a dateTime object', async (t) => {
+      // This is not possible with `now()`:
+      const query = `string(dateTime::now() + 1000)`
+      const tree = parse(query)
+      const value = await evaluate(tree)
+      const data = await value.get()
+      t.type(data, 'string')
+    })
+  })
+
   t.test('upper()', async (t) => {
     t.test('uppercases the given string', async (t) => {
       const tree = parse('upper("abc")')