Make scenario options JSON field optional

Previously, the new scenario `options` field added in #3036 was being
serialized to JSON by default, which made it an incompatible change with
some of our internal Cloud services that validate the existing
configuration structure.

This change makes the object optional, and it will only be serialized if
it's included in the data.

cmd/tests/cmd_run_test.go

@@ -431,7 +431,7 @@ func TestExecutionTestOptionsDefaultValues(t *testing.T) {
 	loglines := ts.LoggerHook.Drain()
 	require.Len(t, loglines, 1)
 
-	expected := `{"paused":null,"executionSegment":null,"executionSegmentSequence":null,"noSetup":null,"setupTimeout":null,"noTeardown":null,"teardownTimeout":null,"rps":null,"dns":{"ttl":null,"select":null,"policy":null},"maxRedirects":null,"userAgent":null,"batch":null,"batchPerHost":null,"httpDebug":null,"insecureSkipTLSVerify":null,"tlsCipherSuites":null,"tlsVersion":null,"tlsAuth":null,"throw":null,"thresholds":null,"blacklistIPs":null,"blockHostnames":null,"hosts":null,"noConnectionReuse":null,"noVUConnectionReuse":null,"minIterationDuration":null,"ext":null,"summaryTrendStats":["avg", "min", "med", "max", "p(90)", "p(95)"],"summaryTimeUnit":null,"systemTags":["check","error","error_code","expected_response","group","method","name","proto","scenario","service","status","subproto","tls_version","url"],"tags":null,"metricSamplesBufferSize":null,"noCookiesReset":null,"discardResponseBodies":null,"consoleOutput":null,"scenarios":{"default":{"vus":null,"iterations":1,"executor":"shared-iterations","maxDuration":null,"options":{"browser":null},"startTime":null,"env":null,"tags":null,"gracefulStop":null,"exec":null}},"localIPs":null}`
+	expected := `{"paused":null,"executionSegment":null,"executionSegmentSequence":null,"noSetup":null,"setupTimeout":null,"noTeardown":null,"teardownTimeout":null,"rps":null,"dns":{"ttl":null,"select":null,"policy":null},"maxRedirects":null,"userAgent":null,"batch":null,"batchPerHost":null,"httpDebug":null,"insecureSkipTLSVerify":null,"tlsCipherSuites":null,"tlsVersion":null,"tlsAuth":null,"throw":null,"thresholds":null,"blacklistIPs":null,"blockHostnames":null,"hosts":null,"noConnectionReuse":null,"noVUConnectionReuse":null,"minIterationDuration":null,"ext":null,"summaryTrendStats":["avg", "min", "med", "max", "p(90)", "p(95)"],"summaryTimeUnit":null,"systemTags":["check","error","error_code","expected_response","group","method","name","proto","scenario","service","status","subproto","tls_version","url"],"tags":null,"metricSamplesBufferSize":null,"noCookiesReset":null,"discardResponseBodies":null,"consoleOutput":null,"scenarios":{"default":{"vus":null,"iterations":1,"executor":"shared-iterations","maxDuration":null,"startTime":null,"env":null,"tags":null,"gracefulStop":null,"exec":null}},"localIPs":null}`
 	assert.JSONEq(t, expected, loglines[0].Message)
 }
 

js/modules/k6/execution/execution_test.go

@@ -211,7 +211,7 @@ func TestOptionsTestFull(t *testing.T) {
 							Tags: map[string]string{
 								"tagkey": "tagvalue",
 							},
-							Options: lib.ScenarioOptions{
+							Options: &lib.ScenarioOptions{
 								Browser: map[string]any{
 									"someOption": true,
 								},

lib/executor/base_config.go

@@ -23,14 +23,14 @@ const executorNameErr = "the executor name should contain only numbers, latin le
 
 // BaseConfig contains the common config fields for all executors
 type BaseConfig struct {
-	Name         string              `json:"-"` // set via the JS object key
-	Type         string              `json:"executor"`
-	StartTime    types.NullDuration  `json:"startTime"`
-	GracefulStop types.NullDuration  `json:"gracefulStop"`
-	Env          map[string]string   `json:"env"`
-	Exec         null.String         `json:"exec"` // function name, externally validated
-	Tags         map[string]string   `json:"tags"`
-	Options      lib.ScenarioOptions `json:"options"`
+	Name         string               `json:"-"` // set via the JS object key
+	Type         string               `json:"executor"`
+	StartTime    types.NullDuration   `json:"startTime"`
+	GracefulStop types.NullDuration   `json:"gracefulStop"`
+	Env          map[string]string    `json:"env"`
+	Exec         null.String          `json:"exec"` // function name, externally validated
+	Tags         map[string]string    `json:"tags"`
+	Options      *lib.ScenarioOptions `json:"options,omitempty"`
 
 	// TODO: future extensions like distribution, others?
 }
@@ -113,7 +113,7 @@ func (bc BaseConfig) GetExec() string {
 
 // GetScenarioOptions returns the options specific to a scenario.
 func (bc BaseConfig) GetScenarioOptions() *lib.ScenarioOptions {
-	return &bc.Options
+	return bc.Options
 }
 
 // GetTags returns any custom tags configured for the executor.

lib/executor/executors_test.go

@@ -472,7 +472,7 @@ func TestArchiveRoundTripScenarioOptions(t *testing.T) {
 						Tags: map[string]string{
 							"tagkey": "tagvalue",
 						},
-						Options: lib.ScenarioOptions{
+						Options: &lib.ScenarioOptions{
 							Browser: map[string]any{
 								"someOption": "someValue",
 							},