Merge pull request #41 from buildkite/group

Add support for group steps

cmd/buildkite-signed-pipeline/signer.go

@@ -40,26 +40,28 @@ func (s SharedSecretSigner) Sign(pipeline interface{}) (interface{}, error) {
 
 	copy := reflect.MakeMap(original.Type())
 
-	// Copy values to new map
 	// TODO handle pipelines of single commands (e.g. `command: foo`)
+	// Iterate over the top level map (where keys are things like, steps, agents, env)
 	for _, mk := range original.MapKeys() {
 		keyName := mk.String()
 		item := original.MapIndex(mk)
 
-		// references many steps
+		// We only care about "steps" at the top level, so dive into this field
 		if strings.EqualFold(keyName, "steps") {
 			unwrapped := item.Elem()
 			if unwrapped.Kind() == reflect.Slice {
+				// newSteps will replace the existing steps. they will be built up with the signature added
 				var newSteps []interface{}
 				for i := 0; i < unwrapped.Len(); i += 1 {
 					stepItem := unwrapped.Index(i)
+					// If the current stepItem is a complex type (list or map)
 					if stepItem.Elem().Kind() != reflect.String {
 						signedStep, err := s.signStep(stepItem)
 						if err != nil {
 							return nil, err
 						}
 						newSteps = append(newSteps, signedStep)
-					} else {
+					} else { // The current stepItem is a plain string (like just `wait` or `block`) so added it without modification
 						newSteps = append(newSteps, stepItem.Interface())
 					}
 				}
@@ -123,6 +125,15 @@ func (s SharedSecretSigner) signStep(step reflect.Value) (interface{}, error) {
 		}
 	}
 
+	// if the step is a `group` we need to recurse to calculate the signature of nested command steps
+	if _, hasGroup := copy["group"]; hasGroup {
+		pipeline := make(map[string]interface{})
+		pipeline["steps"] = copy["steps"]
+		signedGroup, err := s.Sign(pipeline)
+		copy["steps"] = signedGroup.(map[string]interface{})["steps"]
+		return copy, err
+	}
+
 	// extract the plugin declaration for signing
 	extractedPlugins := ""
 	var err error

cmd/buildkite-signed-pipeline/signer_test.go

@@ -75,6 +75,25 @@ func TestSigningCommandWithPlugins(t *testing.T) {
 	assert.Equal(t, "llamas", sig)
 }
 
+func TestSigningCommandWithGroup(t *testing.T) {
+	jsonPipeline := `{"steps":[{"group":"Tests","steps":[{"command":"echo pass"}]}]}`
+
+	var parsed interface{}
+	if err := json.Unmarshal([]byte(jsonPipeline), &parsed); err != nil {
+		t.Fatal(err)
+	}
+
+	signer := NewSharedSecretSigner("secret-llamas")
+
+	signed, err := signer.Sign(parsed)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	j, err := json.Marshal(signed)
+	assert.Equal(t, `{"steps":[{"group":"Tests","steps":[{"command":"echo pass","env":{"STEP_SIGNATURE":"sha256:2c3cb7057477c9630e26532ab6b1707fffc4df3efeb6488bcd9ff2784e1de6fa"}}]}]}`, string(j))
+}
+
 func mapInto(dest interface{}, source interface{}) error {
 	jsonBytes, err := json.Marshal(source)
 	if err != nil {