Alerting: Support for condition field in /api/v1/eval (#79032)

Co-authored-by: Sonia Aguilar <soniaaguilarpeiron@gmail.com>

pkg/tests/api/alerting/api_alertmanager_test.go

@@ -2164,6 +2164,7 @@ func TestIntegrationEval(t *testing.T) {
 							}
 						}
 					],
+				"condition": "A",
 				"now": "2021-04-11T14:38:14Z"
 			}
 			`,
@@ -2221,6 +2222,7 @@ func TestIntegrationEval(t *testing.T) {
 							}
 						}
 					],
+				"condition": "A",
 				"now": "2021-04-11T14:38:14Z"
 			}
 			`,
@@ -2276,6 +2278,7 @@ func TestIntegrationEval(t *testing.T) {
 							}
 						}
 					],
+				"condition": "A",
 				"now": "2021-04-11T14:38:14Z"
 			}
 			`,
@@ -2293,6 +2296,63 @@ func TestIntegrationEval(t *testing.T) {
 				return "Failed to build evaluator for queries and expressions: failed to build query 'A': data source not found"
 			},
 		},
+		{
+			desc: "condition is empty",
+			payload: `
+			{
+				"data": [
+						{
+							"refId": "A",
+							"relativeTimeRange": {
+								"from": 18000,
+								"to": 10800
+							},
+							"datasourceUid": "__expr__",
+							"model": {
+								"type":"math",
+								"expression":"1 > 2"
+							}
+						}
+					],
+				"now": "2021-04-11T14:38:14Z"
+			}
+			`,
+			expectedStatusCode: func() int { return http.StatusOK },
+			expectedMessage:    func() string { return "" },
+			expectedResponse: func() string {
+				return `{
+				"results": {
+				  "A": {
+					"status": 200,
+					"frames": [
+					  {
+						"schema": {
+						  "refId": "A",
+						  "fields": [
+							{
+							  "name": "A",
+							  "type": "number",
+							  "typeInfo": {
+								"frame": "float64",
+								"nullable": true
+							  }
+							}
+						  ]
+						},
+						"data": {
+						  "values": [
+							[
+							  0
+							]
+						  ]
+						}
+					  }
+					]
+				  }
+				}
+			}`
+			},
+		},
 	}
 
 	for _, tc := range testCases {