add support for fetching feature flag payloads (#64)

* add support for fetching feature flag payloads

* improve mock server handler readability

* drying code

* update decide fixtures

* pr feedback

featureflags.go

@@ -50,6 +50,7 @@ type Filter struct {
 	AggregationGroupTypeIndex *uint8                 `json:"aggregation_group_type_index"`
 	Groups                    []FeatureFlagCondition `json:"groups"`
 	Multivariate              *Variants              `json:"multivariate"`
+	Payloads                  map[string]string      `json:"payloads"`
 }
 
 type Variants struct {
@@ -103,7 +104,8 @@ type DecideRequestData struct {
 }
 
 type DecideResponse struct {
-	FeatureFlags map[string]interface{} `json:"featureFlags"`
+	FeatureFlags        map[string]interface{} `json:"featureFlags"`
+	FeatureFlagPayloads map[string]string      `json:"featureFlagPayloads"`
 }
 
 type InconclusiveMatchError struct {
@@ -205,42 +207,28 @@ func (poller *FeatureFlagsPoller) fetchNewFeatureFlags() {
 }
 
 func (poller *FeatureFlagsPoller) GetFeatureFlag(flagConfig FeatureFlagPayload) (interface{}, error) {
-	featureFlags, err := poller.GetFeatureFlags()
-	if err != nil {
-		return nil, err
-	}
-	cohorts := poller.cohorts
-
-	featureFlag := FeatureFlag{Key: ""}
-
-	// avoid using flag for conflicts with Golang's stdlib `flag`
-	for _, storedFlag := range featureFlags {
-		if flagConfig.Key == storedFlag.Key {
-			featureFlag = storedFlag
-			break
-		}
-	}
+	flag, err := poller.getFeatureFlag(flagConfig)
 
 	var result interface{}
 
-	if featureFlag.Key != "" {
+	if flag.Key != "" {
 		result, err = poller.computeFlagLocally(
-			featureFlag,
+			flag,
 			flagConfig.DistinctId,
 			flagConfig.Groups,
 			flagConfig.PersonProperties,
 			flagConfig.GroupProperties,
-			cohorts,
+			poller.cohorts,
 		)
 	}
 
 	if err != nil {
-		poller.Errorf("Unable to compute flag locally (%s) - %s", featureFlag.Key, err)
+		poller.Errorf("Unable to compute flag locally (%s) - %s", flag.Key, err)
 	}
 
 	if (err != nil || result == nil) && !flagConfig.OnlyEvaluateLocally {
 
-		result, err = poller.getFeatureFlagVariant(featureFlag, flagConfig.Key, flagConfig.DistinctId, flagConfig.Groups, flagConfig.PersonProperties, flagConfig.GroupProperties)
+		result, err = poller.getFeatureFlagVariant(flag, flagConfig.Key, flagConfig.DistinctId, flagConfig.Groups, flagConfig.PersonProperties, flagConfig.GroupProperties)
 		if err != nil {
 			return nil, err
 		}
@@ -249,6 +237,63 @@ func (poller *FeatureFlagsPoller) GetFeatureFlag(flagConfig FeatureFlagPayload)
 	return result, err
 }
 
+func (poller *FeatureFlagsPoller) GetFeatureFlagPayload(flagConfig FeatureFlagPayload) (string, error) {
+	flag, err := poller.getFeatureFlag(flagConfig)
+
+	var variant interface{}
+
+	if flag.Key != "" {
+		variant, err = poller.computeFlagLocally(
+			flag,
+			flagConfig.DistinctId,
+			flagConfig.Groups,
+			flagConfig.PersonProperties,
+			flagConfig.GroupProperties,
+			poller.cohorts,
+		)
+	}
+	if err != nil {
+		poller.Errorf("Unable to compute flag locally (%s) - %s", flag.Key, err)
+	}
+
+	if variant != nil {
+		payload, ok := flag.Filters.Payloads[fmt.Sprintf("%v", variant)]
+		if ok {
+			return payload, nil
+		}
+	}
+
+	if (variant == nil || err != nil) && !flagConfig.OnlyEvaluateLocally {
+		result, err := poller.getFeatureFlagPayload(flagConfig.Key, flagConfig.DistinctId, flagConfig.Groups, flagConfig.PersonProperties, flagConfig.GroupProperties)
+		if err != nil {
+			return "", err
+		}
+
+		return result, nil
+	}
+
+	return "", errors.New("unable to compute flag locally")
+}
+
+func (poller *FeatureFlagsPoller) getFeatureFlag(flagConfig FeatureFlagPayload) (FeatureFlag, error) {
+	featureFlags, err := poller.GetFeatureFlags()
+	if err != nil {
+		return FeatureFlag{}, err
+	}
+
+	featureFlag := FeatureFlag{Key: ""}
+
+	// avoid using flag for conflicts with Golang's stdlib `flag`
+	for _, storedFlag := range featureFlags {
+		if flagConfig.Key == storedFlag.Key {
+			featureFlag = storedFlag
+			break
+		}
+	}
+
+	return featureFlag, nil
+}
+
 func (poller *FeatureFlagsPoller) GetAllFlags(flagConfig FeatureFlagPayloadNoKey) (map[string]interface{}, error) {
 	response := map[string]interface{}{}
 	featureFlags, err := poller.GetFeatureFlags()
@@ -285,7 +330,7 @@ func (poller *FeatureFlagsPoller) GetAllFlags(flagConfig FeatureFlagPayloadNoKey
 		if err != nil {
 			return response, err
 		} else {
-			for k, v := range result {
+			for k, v := range result.FeatureFlags {
 				response[k] = v
 			}
 		}
@@ -820,7 +865,7 @@ func (poller *FeatureFlagsPoller) GetFeatureFlags() ([]FeatureFlag, error) {
 }
 
 func (poller *FeatureFlagsPoller) decide(requestData []byte, headers [][2]string) (*http.Response, context.CancelFunc, error) {
-	decideEndpoint := "decide/?v=2"
+	decideEndpoint := "decide/?v=3"
 
 	url, err := url.Parse(poller.Endpoint + "/" + decideEndpoint + "")
 	if err != nil {
@@ -879,7 +924,7 @@ func (poller *FeatureFlagsPoller) shutdownPoller() {
 	poller.shutdown <- true
 }
 
-func (poller *FeatureFlagsPoller) getFeatureFlagVariants(distinctId string, groups Groups, personProperties Properties, groupProperties map[string]Properties) (map[string]interface{}, error) {
+func (poller *FeatureFlagsPoller) getFeatureFlagVariants(distinctId string, groups Groups, personProperties Properties, groupProperties map[string]Properties) (*DecideResponse, error) {
 	errorMessage := "Failed when getting flag variants"
 	requestDataBytes, err := json.Marshal(DecideRequestData{
 		ApiKey:           poller.projectApiKey,
@@ -919,7 +964,7 @@ func (poller *FeatureFlagsPoller) getFeatureFlagVariants(distinctId string, grou
 		return nil, errors.New(errorMessage)
 	}
 
-	return decideResponse.FeatureFlags, nil
+	return &decideResponse, nil
 }
 
 func (poller *FeatureFlagsPoller) getFeatureFlagVariant(featureFlag FeatureFlag, key string, distinctId string, groups Groups, personProperties Properties, groupProperties map[string]Properties) (interface{}, error) {
@@ -948,7 +993,7 @@ func (poller *FeatureFlagsPoller) getFeatureFlagVariant(featureFlag FeatureFlag,
 			return false, variantErr
 		}
 
-		for flagKey, flagValue := range featureFlagVariants {
+		for flagKey, flagValue := range featureFlagVariants.FeatureFlags {
 			flagValueString := fmt.Sprintf("%v", flagValue)
 			if key == flagKey && flagValueString != "false" {
 				result = flagValueString
@@ -960,6 +1005,15 @@ func (poller *FeatureFlagsPoller) getFeatureFlagVariant(featureFlag FeatureFlag,
 	return result, nil
 }
 
+func (poller *FeatureFlagsPoller) getFeatureFlagPayload(key string, distinctId string, groups Groups, personProperties Properties, groupProperties map[string]Properties) (string, error) {
+	featureFlagVariants, err := poller.getFeatureFlagVariants(distinctId, groups, personProperties, groupProperties)
+	if err != nil {
+		return "", err
+	}
+
+	return featureFlagVariants.FeatureFlagPayloads[key], nil
+}
+
 func getSafeProp[T any](properties map[string]any, key string) T {
 	switch v := properties[key].(type) {
 	case T:

fixtures/feature_flag/test-feature-flags-dont-fallback-to-decide-when-only-local-evaluation-is-true.json

@@ -14,7 +14,8 @@
                         "properties": [{"key": "id", "value": 98, "operator": null, "type": "cohort"}],
                         "rollout_percentage": 100
                     }
-                ]
+                ],
+                "payloads": { "true": "{\"test\": 1}" }
             },
             "deleted": false,
             "active": true,

fixtures/feature_flag/test-multivariate-flag.json

@@ -17,6 +17,13 @@
                         {"key": "fourth-variant", "name": "Fourth Variant", "rollout_percentage": 5},
                         {"key": "fifth-variant", "name": "Fifth Variant", "rollout_percentage": 5}
                     ]
+                },
+                "payloads": {
+                    "first-variant": "{\"test\": 1}",
+                    "second-variant": "{\"test\": 2}",
+                    "third-variant": "{\"test\": 3}",
+                    "fourth-variant": "{\"test\": 4}",
+                    "fifth-variant": "{\"test\": 5}"
                 }
             },
             "deleted": false,

fixtures/feature_flag/test-variant-override-clashing.json

@@ -31,7 +31,8 @@
                         {"key": "second-variant", "name": "Second Variant", "rollout_percentage": 25},
                         {"key": "third-variant", "name": "Third Variant", "rollout_percentage": 25}
                     ]
-                }
+                },
+                "payloads": { "first-variant": "{\"test\": 1}", "second-variant": "{\"test\": 2}" }
             },
             "deleted": false,
             "active": true,

fixtures/feature_flag/test-variant-override-invalid.json

@@ -22,7 +22,8 @@
                         {"key": "second-variant", "name": "Second Variant", "rollout_percentage": 25},
                         {"key": "third-variant", "name": "Third Variant", "rollout_percentage": 25}
                     ]
-                }
+                },
+                "payloads": { "third-variant": "{\"test\": 3}", "second-variant": "{\"test\": 2}" }
             },
             "deleted": false,
             "active": true,

fixtures/feature_flag/test-variant-override-multiple.json

@@ -25,7 +25,8 @@
                         {"key": "second-variant", "name": "Second Variant", "rollout_percentage": 25},
                         {"key": "third-variant", "name": "Third Variant", "rollout_percentage": 25}
                     ]
-                }
+                },
+                "payloads": { "third-variant": "{\"test\": 3}", "second-variant": "{\"test\": 2}" }
             },
             "deleted": false,
             "active": true,

fixtures/feature_flag/test-variant-override.json

@@ -22,7 +22,8 @@
                         {"key": "second-variant", "name": "Second Variant", "rollout_percentage": 25},
                         {"key": "third-variant", "name": "Third Variant", "rollout_percentage": 25}
                     ]
-                }
+                },
+                "payloads": { "first-variant": "{\"test\": 1}", "second-variant": "{\"test\": 2}" }
             },
             "deleted": false,
             "active": true,

fixtures/test-api-feature-flag.json

@@ -13,13 +13,33 @@
                         "properties": [],
                         "rollout_percentage": null
                     }
-                ]
+                ],
+                "payloads": { "true": "{\"test\": 1}" }
             },
             "deleted": false,
             "active": true,
             "is_simple_flag": true,
             "rollout_percentage": null
         },
+        {
+            "id": 719,
+            "name": "",
+            "key": "continuation-flag",
+            "filters": {
+                "groups": [
+                    {
+                        "properties": [],
+                        "rollout_percentage": null
+                    }
+                ],
+                "payloads": { "true": "{\"test\": 1}" }
+            },
+            "deleted": false,
+            "active": true,
+            "is_simple_flag": true,
+            "rollout_percentage": null,
+            "ensure_experience_continuity": true
+        },
         {
             "id": 720,
             "name": "",
@@ -30,7 +50,8 @@
                         "properties": [],
                         "rollout_percentage": null
                     }
-                ]
+                ],
+                "payloads": { "true": "{\"test\": 1}", "false": "{\"test\": 0}" }
             },
             "deleted": false,
             "active": true,

fixtures/test-decide-v3.json

@@ -0,0 +1,40 @@
+{
+  "config": {
+    "enable_collect_everything": true
+  },
+  "editorParams": {},
+  "isAuthenticated": true,
+  "supportedCompression": ["gzip", "gzip-js", "lz64"],
+  "toolbarParams": {},
+  "featureFlags": {
+    "enabled-flag": true,
+    "group-flag": true,
+    "disabled-flag": false,
+    "multi-variate-flag": "hello",
+    "simple-flag": true,
+    "beta-feature": "decide-fallback-value",
+    "beta-feature2": "variant-2",
+    "false-flag-2": false,
+    "test-get-feature": "variant-1",
+    "continuation-flag": true
+  },
+  "featureFlagPayloads": {
+    "enabled-flag": "{\"foo\": 1}",
+    "simple-flag": "{\"bar\": 2}",
+    "continuation-flag": "{\"foo\": \"bar\"}",
+    "beta-feature": "{\"foo\": \"bar\"}",
+    "test-get-feature": "this is a string",
+    "multi-variate-flag": "this is the payload"
+  },
+  "sessionRecording": false,
+  "errorsWhileComputingFlags": false,
+  "capturePerformance": false,
+  "autocapture_opt_out": true,
+  "autocaptureExceptions": false,
+  "analytics": { "endpoint": "/i/v0/e/" },
+  "__preview_ingestion_endpoints": true,
+  "elementsChainAsString": true,
+  "surveys": false,
+  "heatmaps": false,
+  "siteApps": []
+}

go.sum

@@ -12,4 +12,4 @@ github.com/shurcooL/sanitized_anchor_name v1.0.0/go.mod h1:1NzhyTcUVG4SuEtjjoZeV
 github.com/urfave/cli v1.22.5 h1:lNq9sAHXK2qfdI8W+GRItjCEkI+2oR4d+MEHy1CKXoU=
 github.com/urfave/cli v1.22.5/go.mod h1:Gos4lmkARVdJ6EkW0WaNv/tZAAMe9V7XWyB60NtXRu0=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
-gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
+gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=