refactor: pass experiment arguments using a struct (#983)

Closes https://github.com/ooni/probe/issues/2358.

internal/engine/experiment/run/dnscheck.go

@@ -21,5 +21,10 @@ func (m *dnsCheckMain) do(ctx context.Context, input StructuredInput,
 	measurement.TestName = exp.ExperimentName()
 	measurement.TestVersion = exp.ExperimentVersion()
 	measurement.Input = model.MeasurementTarget(input.Input)
-	return exp.Run(ctx, sess, measurement, callbacks)
+	args := &model.ExperimentArgs{
+		Callbacks:   callbacks,
+		Measurement: measurement,
+		Session:     sess,
+	}
+	return exp.Run(ctx, args)
 }

internal/engine/experiment/run/run.go

@@ -46,10 +46,10 @@ type StructuredInput struct {
 }
 
 // Run implements ExperimentMeasurer.ExperimentVersion.
-func (Measurer) Run(
-	ctx context.Context, sess model.ExperimentSession,
-	measurement *model.Measurement, callbacks model.ExperimentCallbacks,
-) error {
+func (Measurer) Run(ctx context.Context, args *model.ExperimentArgs) error {
+	callbacks := args.Callbacks
+	measurement := args.Measurement
+	sess := args.Session
 	var input StructuredInput
 	if err := json.Unmarshal([]byte(measurement.Input), &input); err != nil {
 		return err

internal/engine/experiment/run/run_test.go

@@ -31,7 +31,12 @@ func TestRunDNSCheckWithCancelledContext(t *testing.T) {
 	cancel() // fail immediately
 	sess := &mockable.Session{MockableLogger: log.Log}
 	callbacks := model.NewPrinterCallbacks(log.Log)
-	err := measurer.Run(ctx, sess, measurement, callbacks)
+	args := &model.ExperimentArgs{
+		Callbacks:   callbacks,
+		Measurement: measurement,
+		Session:     sess,
+	}
+	err := measurer.Run(ctx, args)
 	// TODO(bassosimone): here we could improve the tests by checking
 	// whether the result makes sense for a cancelled context.
 	if err != nil {
@@ -62,7 +67,12 @@ func TestRunURLGetterWithCancelledContext(t *testing.T) {
 	cancel() // fail immediately
 	sess := &mockable.Session{MockableLogger: log.Log}
 	callbacks := model.NewPrinterCallbacks(log.Log)
-	err := measurer.Run(ctx, sess, measurement, callbacks)
+	args := &model.ExperimentArgs{
+		Callbacks:   callbacks,
+		Measurement: measurement,
+		Session:     sess,
+	}
+	err := measurer.Run(ctx, args)
 	if err != nil { // here we expected nil b/c we want to submit the measurement
 		t.Fatal(err)
 	}
@@ -86,7 +96,12 @@ func TestRunWithInvalidJSON(t *testing.T) {
 	ctx := context.Background()
 	sess := &mockable.Session{MockableLogger: log.Log}
 	callbacks := model.NewPrinterCallbacks(log.Log)
-	err := measurer.Run(ctx, sess, measurement, callbacks)
+	args := &model.ExperimentArgs{
+		Callbacks:   callbacks,
+		Measurement: measurement,
+		Session:     sess,
+	}
+	err := measurer.Run(ctx, args)
 	if err == nil || err.Error() != "invalid character '}' looking for beginning of value" {
 		t.Fatalf("not the error we expected: %+v", err)
 	}
@@ -100,7 +115,12 @@ func TestRunWithUnknownExperiment(t *testing.T) {
 	ctx := context.Background()
 	sess := &mockable.Session{MockableLogger: log.Log}
 	callbacks := model.NewPrinterCallbacks(log.Log)
-	err := measurer.Run(ctx, sess, measurement, callbacks)
+	args := &model.ExperimentArgs{
+		Callbacks:   callbacks,
+		Measurement: measurement,
+		Session:     sess,
+	}
+	err := measurer.Run(ctx, args)
 	if err == nil || err.Error() != "no such experiment: antani" {
 		t.Fatalf("not the error we expected: %+v", err)
 	}

internal/engine/experiment/run/urlgetter.go

@@ -18,5 +18,10 @@ func (m *urlGetterMain) do(ctx context.Context, input StructuredInput,
 	measurement.TestName = exp.ExperimentName()
 	measurement.TestVersion = exp.ExperimentVersion()
 	measurement.Input = model.MeasurementTarget(input.Input)
-	return exp.Run(ctx, sess, measurement, callbacks)
+	args := &model.ExperimentArgs{
+		Callbacks:   callbacks,
+		Measurement: measurement,
+		Session:     sess,
+	}
+	return exp.Run(ctx, args)
 }