feat: pass tracker's config into TrackRequest (#210)

This PR improves the ergonomics of `TrackRequest`. The user callback now
receives a `Config` directly, which can be accessed to provide
parameters for the request.

An alternative would be directly exposing the `Config` as a public
variable of `Tracker`, or forcing the user to instead reference the
config returned from a call to `cfg, tracker := client.Config(..)`.

Those alternatives are not great, because they make the user carry
around the config and manually inject it into the callback. This way,
the callback can be defined wherever and not need to worry about how to
receive the config.

ldai/tracker.go

@@ -200,25 +200,26 @@ func (t *Tracker) TrackUsage(usage TokenUsage) error {
 	return nil
 }
 
-func measureDurationOfTask[T any](stopwatch Stopwatch, task func() (T, error)) (T, time.Duration, error) {
+func measureDurationOfTask[T any, A any](stopwatch Stopwatch, arg A, task func(A) (T, error)) (T, time.Duration, error) {
 	stopwatch.Start()
-	result, err := task()
+	result, err := task(arg)
 	return result, stopwatch.Stop(), err
 }
 
 // TrackRequest tracks metrics for a model evaluation request. The task function should return a ProviderResponse
-// which can be used to specify request metrics and token usage.
+// which can be used to specify request metrics and token usage. All fields of the returned ProviderResponse are optional.
 //
-// All fields of the ProviderResponse are optional.
+// The task function will be passed the current AI config, which can be used to obtain any parameters or messages
+// relevant to the request.
 //
 // If the task returns an error, then the request is not considered successful and no metrics are tracked.
 // Otherwise, the following metrics are tracked:
 //  1. Successful model evaluation.
 //  2. Any metrics that were that set in the ProviderResponse
 //     2a) If Latency was not set in the ProviderResponse's Metrics field, an automatically measured duration.
 //  3. Any token usage that was set in the ProviderResponse.
-func (t *Tracker) TrackRequest(task func() (ProviderResponse, error)) (ProviderResponse, error) {
-	usage, duration, err := measureDurationOfTask(t.stopwatch, task)
+func (t *Tracker) TrackRequest(task func(c *Config) (ProviderResponse, error)) (ProviderResponse, error) {
+	usage, duration, err := measureDurationOfTask(t.stopwatch, t.config, task)
 
 	if err != nil {
 		t.logWarning("error executing request: %v", err)

ldai/tracker_test.go

@@ -1,6 +1,7 @@
 package ldai
 
 import (
+	"github.com/launchdarkly/go-server-sdk/ldai/datamodel"
 	"testing"
 	"time"
 
@@ -78,7 +79,7 @@ func TestTracker_TrackRequest(t *testing.T) {
 		},
 	}
 
-	r, err := tracker.TrackRequest(func() (ProviderResponse, error) {
+	r, err := tracker.TrackRequest(func(c *Config) (ProviderResponse, error) {
 		return expectedResponse, nil
 	})
 
@@ -110,6 +111,29 @@ func TestTracker_TrackRequest(t *testing.T) {
 	assert.ElementsMatch(t, expectedEvents, events.events)
 }
 
+func TestTracker_TrackRequestReceivesConfig(t *testing.T) {
+	events := newMockEvents()
+
+	expectedConfig := NewConfig().
+		WithMessage("hello", datamodel.Assistant).
+		WithModelId("model").
+		WithProviderId("provider").
+		WithModelParam("param", ldvalue.String("value")).
+		WithCustomModelParam("custom", ldvalue.String("value")).
+		Enable().
+		Build()
+
+	tracker := newTracker("key", "versionKey", events, &expectedConfig, ldcontext.New("key"), nil)
+
+	var gotConfig *Config
+	_, _ = tracker.TrackRequest(func(c *Config) (ProviderResponse, error) {
+		gotConfig = c
+		return ProviderResponse{}, nil
+	})
+
+	assert.Equal(t, expectedConfig, *gotConfig)
+}
+
 type mockStopwatch time.Duration
 
 func (m mockStopwatch) Start() {}
@@ -130,7 +154,7 @@ func TestTracker_LatencyMeasuredIfNotProvided(t *testing.T) {
 		},
 	}
 
-	r, err := tracker.TrackRequest(func() (ProviderResponse, error) {
+	r, err := tracker.TrackRequest(func(c *Config) (ProviderResponse, error) {
 		return expectedResponse, nil
 	})