CloudWatch - Enable list_metrics() with Dimensions without value (#4400)

moto/cloudwatch/models.py

@@ -35,7 +35,9 @@ class Dimension(object):
 
     def __eq__(self, item):
         if isinstance(item, Dimension):
-            return self.name == item.name and self.value == item.value
+            return self.name == item.name and (
+                self.value is None or item.value is None or self.value == item.value
+            )
         return False
 
     def __ne__(self, item):  # Only needed on Py2; Py3 defines it implicitly
@@ -222,7 +224,8 @@ class MetricDatum(BaseModel):
                 return False
 
         if dimensions and any(
-            Dimension(d["Name"], d["Value"]) not in self.dimensions for d in dimensions
+            Dimension(d["Name"], d.get("Value")) not in self.dimensions
+            for d in dimensions
         ):
             return False
         return True

moto/cloudwatch/responses.py

@@ -212,7 +212,7 @@ class CloudWatchResponse(BaseResponse):
     def list_metrics(self):
         namespace = self._get_param("Namespace")
         metric_name = self._get_param("MetricName")
-        dimensions = self._get_multi_param("Dimensions.member")
+        dimensions = self._get_params().get("Dimensions", [])
         next_token = self._get_param("NextToken")
         next_token, metrics = self.cloudwatch_backend.list_metrics(
             next_token, namespace, metric_name, dimensions

tests/test_cloudwatch/test_cloudwatch_boto3.py

@@ -379,6 +379,25 @@ def test_list_metrics_paginated():
     )
 
 
+@mock_cloudwatch
+def test_list_metrics_without_value():
+    cloudwatch = boto3.client("cloudwatch", "eu-west-1")
+    # Create some metrics to filter on
+    create_metrics_with_dimensions(cloudwatch, namespace="MyNamespace", data_points=3)
+    # Verify we can filter by namespace/metric name
+    res = cloudwatch.list_metrics(Namespace="MyNamespace")["Metrics"]
+    res.should.have.length_of(3)
+    # Verify we can filter by Dimension without value
+    results = cloudwatch.list_metrics(
+        Namespace="MyNamespace", MetricName="MyMetric", Dimensions=[{"Name": "D1"}]
+    )["Metrics"]
+
+    results.should.have.length_of(1)
+    results[0]["Namespace"].should.equals("MyNamespace")
+    results[0]["MetricName"].should.equal("MyMetric")
+    results[0]["Dimensions"].should.equal([{"Name": "D1", "Value": "V1"}])
+
+
 def create_metrics(cloudwatch, namespace, metrics=5, data_points=5):
     for i in range(0, metrics):
         metric_name = "metric" + str(i)
@@ -389,6 +408,20 @@ def create_metrics(cloudwatch, namespace, metrics=5, data_points=5):
             )
 
 
+def create_metrics_with_dimensions(cloudwatch, namespace, data_points=5):
+    for j in range(0, data_points):
+        cloudwatch.put_metric_data(
+            Namespace=namespace,
+            MetricData=[
+                {
+                    "MetricName": "MyMetric",
+                    "Dimensions": [{"Name": f"D{j}", "Value": f"V{j}"}],
+                    "Unit": "Seconds",
+                }
+            ],
+        )
+
+
 @mock_cloudwatch
 def test_get_metric_data_within_timeframe():
     utc_now = datetime.now(tz=pytz.utc)