feat: Add a configurable error handler for environment updates. Return response codes on HTTP errors

client.go

@@ -31,6 +31,7 @@ type Client struct {
 	ctxAnalytics   context.Context
 	log            Logger
 	offlineHandler OfflineHandler
+	errorHandler   func(handler FlagsmithErrorHandler)
 }
 
 // NewClient creates instance of Client with given configuration.
@@ -267,10 +268,18 @@ func (c *Client) UpdateEnvironment(ctx context.Context) error {
 		Get(c.config.baseURL + "environment-document/")
 
 	if err != nil {
-		return &FlagsmithAPIError{msg: fmt.Sprintf("flagsmith: error performing request to Flagsmith API: %s", err)}
+		f := &FlagsmithAPIError{msg: fmt.Sprintf("flagsmith: error performing request to Flagsmith API: %s", err)}
+		if c.errorHandler != nil {
+			c.errorHandler(FlagsmithErrorHandler{err, resp.StatusCode(), resp.Status()})
+		}
+		return f
 	}
 	if resp.StatusCode() != 200 {
-		return &FlagsmithAPIError{msg: fmt.Sprintf("flagsmith: unexpected response from Flagsmith API: %s", resp.Status())}
+		f := &FlagsmithAPIError{msg: fmt.Sprintf("flagsmith: unexpected response from Flagsmith API: %s", resp.Status())}
+		if c.errorHandler != nil {
+			c.errorHandler(FlagsmithErrorHandler{err, resp.StatusCode(), resp.Status()})
+		}
+		return f
 	}
 	c.environment.Store(&env)
 	identitiesWithOverrides := make(map[string]identities.IdentityModel)

client_test.go

@@ -675,3 +675,35 @@ func TestOfflineHandlerIsUsedWhenRequestFails(t *testing.T) {
 	assert.Equal(t, fixtures.Feature1ID, allFlags[0].FeatureID)
 	assert.Equal(t, fixtures.Feature1Value, allFlags[0].Value)
 }
+
+func TestPollErrorHandlerIsUsedWhenPollFails(t *testing.T) {
+	// Given
+	ctx := context.Background()
+	var capturedError error
+	var statusCode int
+	var status string
+
+	server := httptest.NewServer(http.HandlerFunc(func(rw http.ResponseWriter, req *http.Request) {
+		rw.WriteHeader(http.StatusInternalServerError)
+	}))
+	defer server.Close()
+
+	// When
+	client := flagsmith.NewClient(fixtures.EnvironmentAPIKey,
+		flagsmith.WithBaseURL(server.URL+"/api/v1/"),
+		flagsmith.WithEnvironmentRefreshInterval(time.Duration(2)*time.Second),
+		flagsmith.WithErrorHandler(func(handler flagsmith.FlagsmithErrorHandler) {
+			capturedError = handler.Err
+			statusCode = handler.ResponseStatusCode
+			status = handler.ResponseStatus
+		}),
+	)
+
+	// when
+	_ = client.UpdateEnvironment(ctx)
+
+	// Then
+	assert.Equal(t, capturedError, nil)
+	assert.Equal(t, statusCode, 500)
+	assert.Equal(t, status, "500 Internal Server Error")
+}

errors.go

@@ -8,6 +8,12 @@ type FlagsmithAPIError struct {
 	msg string
 }
 
+type FlagsmithErrorHandler struct {
+	Err                error
+	ResponseStatusCode int
+	ResponseStatus     string
+}
+
 func (e FlagsmithClientError) Error() string {
 	return e.msg
 }

options.go

@@ -117,3 +117,10 @@
 		c.config.offlineMode = true
 	}
 }
+
+// WithErrorHandler provides a way to handle errors that occur during update of an environment
+func WithErrorHandler(handler func(handler FlagsmithErrorHandler)) Option {
+	return func(c *Client) {
+		c.errorHandler = handler
+	}
+}