Implement support for NOW variable #207

bwaldvogel · bwaldvogel · commit 0e99c45933c4 · 2022-11-24T11:40:51.000+01:00
diff --git a/core/src/main/java/de/bwaldvogel/mongo/backend/aggregation/Expression.java b/core/src/main/java/de/bwaldvogel/mongo/backend/aggregation/Expression.java
@@ -1784,20 +1784,23 @@ static Object evaluate(Object expression, Document document) {
                 if (variableValue instanceof Missing) {
                     if (variableName.equals("$ROOT")) {
                         variableValue = document;
+                    } else if (variableName.equals("$NOW")) {
+                        variableValue = Instant.now();
                     } else {
                         throw new MongoServerError(17276, "Use of undefined variable: " + variableName.substring(1));
                     }
                 }
 
+                if (variableValue instanceof String) {
+                    String variableValueString = (String) variableValue;
+                    if (variableValueString.startsWith("$")) {
+                        variableValue = evaluate(variableValue, document);
+                    }
+                }
+
                 if (!value.equals(variableName)) {
                     String path = value.substring(variableName.length() + 1);
-                    final Document evaluatedVariableValue;
-                    if (variableValue instanceof Document) {
-                        evaluatedVariableValue = (Document) variableValue;
-                    } else {
-                        evaluatedVariableValue = (Document) evaluate(variableValue, document);
-                    }
-                    return Utils.getSubdocumentValue(evaluatedVariableValue, path);
+                    return Utils.getSubdocumentValue((Document) variableValue, path);
                 } else {
                     return variableValue;
                 }
diff --git a/test-common/src/main/java/de/bwaldvogel/mongo/backend/AbstractAggregationTest.java b/test-common/src/main/java/de/bwaldvogel/mongo/backend/AbstractAggregationTest.java
@@ -2501,6 +2501,23 @@ void testAggregateWithMerge_pipeline_newVariable() throws Exception {
             .containsExactly(json("_id: 1, b: 'xyz', a: 1"));
     }
 
+    @Test
+    void testAggregateWithMerge_pipeline_nowVariable() throws Exception {
+        collection.insertOne(json("_id: 1"));
+
+        MongoCollection<Document> otherCollection = db.getCollection("other");
+        otherCollection.insertOne(json("_id: 1"));
+
+        Instant instantBefore = Instant.now();
+        Document result = collection.aggregate(
+            jsonList("$merge: {into: 'other', let: {now: '$$NOW'}, whenMatched: [{$addFields: {timestamp: '$$now'}}]}")).first();
+        Instant instantAfter = Instant.now();
+
+        assertThat(result).containsOnlyKeys("_id", "timestamp");
+        System.out.println(result.get("timestamp"));
+        assertThat(result.getDate("timestamp")).isBetween(instantBefore, instantAfter);
+    }
+
     private static Stream<Arguments> aggregateWithMerge_illegalParametersArguments() {
         return Stream.of(
             Arguments.of("$merge: null", IllegalStateException.class,
diff --git a/test-common/src/main/java/de/bwaldvogel/mongo/backend/AbstractTest.java b/test-common/src/main/java/de/bwaldvogel/mongo/backend/AbstractTest.java
@@ -1,10 +1,14 @@
 package de.bwaldvogel.mongo.backend;
 
+import java.time.Instant;
 import java.util.ArrayList;
+import java.util.Date;
 import java.util.List;
 
 import org.assertj.core.api.AbstractBooleanAssert;
+import org.assertj.core.api.AbstractDateAssert;
 import org.assertj.core.api.AbstractDoubleAssert;
+import org.assertj.core.api.AbstractInstantAssert;
 import org.assertj.core.api.AbstractIntegerAssert;
 import org.assertj.core.api.AbstractLongAssert;
 import org.assertj.core.api.AbstractStringAssert;
@@ -170,6 +174,14 @@ protected static AbstractBooleanAssert<?> assertThat(Boolean actual) {
         return Assertions.assertThat(actual);
     }
 
+    protected static AbstractInstantAssert<?> assertThat(Instant actual) {
+        return Assertions.assertThat(actual);
+    }
+
+    protected static AbstractDateAssert<?> assertThat(Date actual) {
+        return Assertions.assertThat(actual);
+    }
+
     protected static <T> IterableAssert<T> assertThat(Iterable<T> actual) {
         // improve assertion array by collection entire array
         List<T> values = TestUtils.toArray(actual);
