Add WebhookTypes and EventForType methods (google#2865)

Fixes: google#2863.

github/event.go

@@ -27,139 +27,16 @@ func (e Event) String() string {
 
 // ParsePayload parses the event payload. For recognized event types,
 // a value of the corresponding struct type will be returned.
-func (e *Event) ParsePayload() (payload interface{}, err error) {
-	switch *e.Type {
-	case "BranchProtectionRuleEvent":
-		payload = &BranchProtectionRuleEvent{}
-	case "CheckRunEvent":
-		payload = &CheckRunEvent{}
-	case "CheckSuiteEvent":
-		payload = &CheckSuiteEvent{}
-	case "CodeScanningAlertEvent":
-		payload = &CodeScanningAlertEvent{}
-	case "CommitCommentEvent":
-		payload = &CommitCommentEvent{}
-	case "ContentReferenceEvent":
-		payload = &ContentReferenceEvent{}
-	case "CreateEvent":
-		payload = &CreateEvent{}
-	case "DeleteEvent":
-		payload = &DeleteEvent{}
-	case "DeployKeyEvent":
-		payload = &DeployKeyEvent{}
-	case "DeploymentEvent":
-		payload = &DeploymentEvent{}
-	case "DeploymentProtectionRuleEvent":
-		payload = &DeploymentProtectionRuleEvent{}
-	case "DeploymentStatusEvent":
-		payload = &DeploymentStatusEvent{}
-	case "DiscussionEvent":
-		payload = &DiscussionEvent{}
-	case "DiscussionCommentEvent":
-		payload = &DiscussionCommentEvent{}
-	case "ForkEvent":
-		payload = &ForkEvent{}
-	case "GitHubAppAuthorizationEvent":
-		payload = &GitHubAppAuthorizationEvent{}
-	case "GollumEvent":
-		payload = &GollumEvent{}
-	case "InstallationEvent":
-		payload = &InstallationEvent{}
-	case "InstallationRepositoriesEvent":
-		payload = &InstallationRepositoriesEvent{}
-	case "InstallationTargetEvent":
-		payload = &InstallationTargetEvent{}
-	case "IssueCommentEvent":
-		payload = &IssueCommentEvent{}
-	case "IssuesEvent":
-		payload = &IssuesEvent{}
-	case "LabelEvent":
-		payload = &LabelEvent{}
-	case "MarketplacePurchaseEvent":
-		payload = &MarketplacePurchaseEvent{}
-	case "MemberEvent":
-		payload = &MemberEvent{}
-	case "MembershipEvent":
-		payload = &MembershipEvent{}
-	case "MergeGroupEvent":
-		payload = &MergeGroupEvent{}
-	case "MetaEvent":
-		payload = &MetaEvent{}
-	case "MilestoneEvent":
-		payload = &MilestoneEvent{}
-	case "OrganizationEvent":
-		payload = &OrganizationEvent{}
-	case "OrgBlockEvent":
-		payload = &OrgBlockEvent{}
-	case "PackageEvent":
-		payload = &PackageEvent{}
-	case "PageBuildEvent":
-		payload = &PageBuildEvent{}
-	case "PersonalAccessTokenRequestEvent":
-		payload = &PersonalAccessTokenRequestEvent{}
-	case "PingEvent":
-		payload = &PingEvent{}
-	case "ProjectEvent":
-		payload = &ProjectEvent{}
-	case "ProjectCardEvent":
-		payload = &ProjectCardEvent{}
-	case "ProjectColumnEvent":
-		payload = &ProjectColumnEvent{}
-	case "ProjectV2Event":
-		payload = &ProjectV2Event{}
-	case "ProjectV2ItemEvent":
-		payload = &ProjectV2ItemEvent{}
-	case "PublicEvent":
-		payload = &PublicEvent{}
-	case "PullRequestEvent":
-		payload = &PullRequestEvent{}
-	case "PullRequestReviewEvent":
-		payload = &PullRequestReviewEvent{}
-	case "PullRequestReviewCommentEvent":
-		payload = &PullRequestReviewCommentEvent{}
-	case "PullRequestReviewThreadEvent":
-		payload = &PullRequestReviewThreadEvent{}
-	case "PullRequestTargetEvent":
-		payload = &PullRequestTargetEvent{}
-	case "PushEvent":
-		payload = &PushEvent{}
-	case "ReleaseEvent":
-		payload = &ReleaseEvent{}
-	case "RepositoryEvent":
-		payload = &RepositoryEvent{}
-	case "RepositoryDispatchEvent":
-		payload = &RepositoryDispatchEvent{}
-	case "RepositoryImportEvent":
-		payload = &RepositoryImportEvent{}
-	case "RepositoryVulnerabilityAlertEvent":
-		payload = &RepositoryVulnerabilityAlertEvent{}
-	case "SecretScanningAlertEvent":
-		payload = &SecretScanningAlertEvent{}
-	case "SecurityAdvisoryEvent":
-		payload = &SecurityAdvisoryEvent{}
-	case "SecurityAndAnalysisEvent":
-		payload = &SecurityAndAnalysisEvent{}
-	case "StarEvent":
-		payload = &StarEvent{}
-	case "StatusEvent":
-		payload = &StatusEvent{}
-	case "TeamEvent":
-		payload = &TeamEvent{}
-	case "TeamAddEvent":
-		payload = &TeamAddEvent{}
-	case "UserEvent":
-		payload = &UserEvent{}
-	case "WatchEvent":
-		payload = &WatchEvent{}
-	case "WorkflowDispatchEvent":
-		payload = &WorkflowDispatchEvent{}
-	case "WorkflowJobEvent":
-		payload = &WorkflowJobEvent{}
-	case "WorkflowRunEvent":
-		payload = &WorkflowRunEvent{}
+func (e *Event) ParsePayload() (interface{}, error) {
+	// It would be nice if e.Type were the snake_case name of the event,
+	// but the existing interface uses the struct name instead.
+	payload := EventForType(typeToMessageMapping[e.GetType()])
+
+	if err := json.Unmarshal(e.GetRawPayload(), &payload); err != nil {
+		return nil, err
 	}
-	err = json.Unmarshal(*e.RawPayload, &payload)
-	return payload, err
+
+	return payload, nil
 }
 
 // Payload returns the parsed event payload. For recognized event types,

github/event_test.go

@@ -30,6 +30,18 @@ func TestPayload_NoPanic(t *testing.T) {
 	e.Payload()
 }
 
+func TestEmptyEvent_NoPanic(t *testing.T) {
+	e := &Event{}
+	if _, err := e.ParsePayload(); err == nil {
+		t.Error("ParsePayload unexpectedly succeeded on empty event")
+	}
+
+	e = nil
+	if _, err := e.ParsePayload(); err == nil {
+		t.Error("ParsePayload unexpectedly succeeded on nil event")
+	}
+}
+
 func TestEvent_Marshal(t *testing.T) {
 	testJSONMarshal(t, &Event{}, "{}")
 

github/messages.go

@@ -22,6 +22,8 @@ import (
 	"mime"
 	"net/http"
 	"net/url"
+	"reflect"
+	"sort"
 	"strings"
 )
 
@@ -43,74 +45,86 @@ const (
 
 var (
 	// eventTypeMapping maps webhooks types to their corresponding go-github struct types.
-	eventTypeMapping = map[string]string{
-		"branch_protection_rule":         "BranchProtectionRuleEvent",
-		"check_run":                      "CheckRunEvent",
-		"check_suite":                    "CheckSuiteEvent",
-		"code_scanning_alert":            "CodeScanningAlertEvent",
-		"commit_comment":                 "CommitCommentEvent",
-		"content_reference":              "ContentReferenceEvent",
-		"create":                         "CreateEvent",
-		"delete":                         "DeleteEvent",
-		"deploy_key":                     "DeployKeyEvent",
-		"deployment":                     "DeploymentEvent",
-		"deployment_status":              "DeploymentStatusEvent",
-		"deployment_protection_rule":     "DeploymentProtectionRuleEvent",
-		"discussion":                     "DiscussionEvent",
-		"discussion_comment":             "DiscussionCommentEvent",
-		"fork":                           "ForkEvent",
-		"github_app_authorization":       "GitHubAppAuthorizationEvent",
-		"gollum":                         "GollumEvent",
-		"installation":                   "InstallationEvent",
-		"installation_repositories":      "InstallationRepositoriesEvent",
-		"installation_target":            "InstallationTargetEvent",
-		"issue_comment":                  "IssueCommentEvent",
-		"issues":                         "IssuesEvent",
-		"label":                          "LabelEvent",
-		"marketplace_purchase":           "MarketplacePurchaseEvent",
-		"member":                         "MemberEvent",
-		"membership":                     "MembershipEvent",
-		"merge_group":                    "MergeGroupEvent",
-		"meta":                           "MetaEvent",
-		"milestone":                      "MilestoneEvent",
-		"organization":                   "OrganizationEvent",
-		"org_block":                      "OrgBlockEvent",
-		"package":                        "PackageEvent",
-		"page_build":                     "PageBuildEvent",
-		"personal_access_token_request":  "PersonalAccessTokenRequestEvent",
-		"ping":                           "PingEvent",
-		"project":                        "ProjectEvent",
-		"project_card":                   "ProjectCardEvent",
-		"project_column":                 "ProjectColumnEvent",
-		"projects_v2":                    "ProjectV2Event",
-		"projects_v2_item":               "ProjectV2ItemEvent",
-		"public":                         "PublicEvent",
-		"pull_request":                   "PullRequestEvent",
-		"pull_request_review":            "PullRequestReviewEvent",
-		"pull_request_review_comment":    "PullRequestReviewCommentEvent",
-		"pull_request_review_thread":     "PullRequestReviewThreadEvent",
-		"pull_request_target":            "PullRequestTargetEvent",
-		"push":                           "PushEvent",
-		"repository":                     "RepositoryEvent",
-		"repository_dispatch":            "RepositoryDispatchEvent",
-		"repository_import":              "RepositoryImportEvent",
-		"repository_vulnerability_alert": "RepositoryVulnerabilityAlertEvent",
-		"release":                        "ReleaseEvent",
-		"secret_scanning_alert":          "SecretScanningAlertEvent",
-		"security_advisory":              "SecurityAdvisoryEvent",
-		"security_and_analysis":          "SecurityAndAnalysisEvent",
-		"star":                           "StarEvent",
-		"status":                         "StatusEvent",
-		"team":                           "TeamEvent",
-		"team_add":                       "TeamAddEvent",
-		"user":                           "UserEvent",
-		"watch":                          "WatchEvent",
-		"workflow_dispatch":              "WorkflowDispatchEvent",
-		"workflow_job":                   "WorkflowJobEvent",
-		"workflow_run":                   "WorkflowRunEvent",
+	eventTypeMapping = map[string]interface{}{
+		"branch_protection_rule":         &BranchProtectionRuleEvent{},
+		"check_run":                      &CheckRunEvent{},
+		"check_suite":                    &CheckSuiteEvent{},
+		"code_scanning_alert":            &CodeScanningAlertEvent{},
+		"commit_comment":                 &CommitCommentEvent{},
+		"content_reference":              &ContentReferenceEvent{},
+		"create":                         &CreateEvent{},
+		"delete":                         &DeleteEvent{},
+		"deploy_key":                     &DeployKeyEvent{},
+		"deployment":                     &DeploymentEvent{},
+		"deployment_status":              &DeploymentStatusEvent{},
+		"deployment_protection_rule":     &DeploymentProtectionRuleEvent{},
+		"discussion":                     &DiscussionEvent{},
+		"discussion_comment":             &DiscussionCommentEvent{},
+		"fork":                           &ForkEvent{},
+		"github_app_authorization":       &GitHubAppAuthorizationEvent{},
+		"gollum":                         &GollumEvent{},
+		"installation":                   &InstallationEvent{},
+		"installation_repositories":      &InstallationRepositoriesEvent{},
+		"installation_target":            &InstallationTargetEvent{},
+		"issue_comment":                  &IssueCommentEvent{},
+		"issues":                         &IssuesEvent{},
+		"label":                          &LabelEvent{},
+		"marketplace_purchase":           &MarketplacePurchaseEvent{},
+		"member":                         &MemberEvent{},
+		"membership":                     &MembershipEvent{},
+		"merge_group":                    &MergeGroupEvent{},
+		"meta":                           &MetaEvent{},
+		"milestone":                      &MilestoneEvent{},
+		"organization":                   &OrganizationEvent{},
+		"org_block":                      &OrgBlockEvent{},
+		"package":                        &PackageEvent{},
+		"page_build":                     &PageBuildEvent{},
+		"personal_access_token_request":  &PersonalAccessTokenRequestEvent{},
+		"ping":                           &PingEvent{},
+		"project":                        &ProjectEvent{},
+		"project_card":                   &ProjectCardEvent{},
+		"project_column":                 &ProjectColumnEvent{},
+		"projects_v2":                    &ProjectV2Event{},
+		"projects_v2_item":               &ProjectV2ItemEvent{},
+		"public":                         &PublicEvent{},
+		"pull_request":                   &PullRequestEvent{},
+		"pull_request_review":            &PullRequestReviewEvent{},
+		"pull_request_review_comment":    &PullRequestReviewCommentEvent{},
+		"pull_request_review_thread":     &PullRequestReviewThreadEvent{},
+		"pull_request_target":            &PullRequestTargetEvent{},
+		"push":                           &PushEvent{},
+		"repository":                     &RepositoryEvent{},
+		"repository_dispatch":            &RepositoryDispatchEvent{},
+		"repository_import":              &RepositoryImportEvent{},
+		"repository_vulnerability_alert": &RepositoryVulnerabilityAlertEvent{},
+		"release":                        &ReleaseEvent{},
+		"secret_scanning_alert":          &SecretScanningAlertEvent{},
+		"security_advisory":              &SecurityAdvisoryEvent{},
+		"security_and_analysis":          &SecurityAndAnalysisEvent{},
+		"star":                           &StarEvent{},
+		"status":                         &StatusEvent{},
+		"team":                           &TeamEvent{},
+		"team_add":                       &TeamAddEvent{},
+		"user":                           &UserEvent{},
+		"watch":                          &WatchEvent{},
+		"workflow_dispatch":              &WorkflowDispatchEvent{},
+		"workflow_job":                   &WorkflowJobEvent{},
+		"workflow_run":                   &WorkflowRunEvent{},
 	}
+	// forward mapping of event types to the string names of the structs
+	messageToTypeName = make(map[string]string, len(eventTypeMapping))
+	// Inverse map of the above
+	typeToMessageMapping = make(map[string]string, len(eventTypeMapping))
 )
 
+func init() {
+	for k, v := range eventTypeMapping {
+		typename := reflect.TypeOf(v).Elem().Name()
+		messageToTypeName[k] = typename
+		typeToMessageMapping[typename] = k
+	}
+}
+
 // genMAC generates the HMAC signature for a message provided the secret key
 // and hashFunc.
 func genMAC(message, key []byte, hashFunc func() hash.Hash) []byte {
@@ -299,7 +313,7 @@ func DeliveryID(r *http.Request) string {
 //	  }
 //	}
 func ParseWebHook(messageType string, payload []byte) (interface{}, error) {
-	eventType, ok := eventTypeMapping[messageType]
+	eventType, ok := messageToTypeName[messageType]
 	if !ok {
 		return nil, fmt.Errorf("unknown X-Github-Event in message: %v", messageType)
 	}
@@ -310,3 +324,28 @@ func ParseWebHook(messageType string, payload []byte) (interface{}, error) {
 	}
 	return event.ParsePayload()
 }
+
+// WebhookTypes returns a sorted list of all the known GitHub event type strings
+// supported by go-github.
+func MessageTypes() []string {
+	types := make([]string, 0, len(eventTypeMapping))
+	for t := range eventTypeMapping {
+		types = append(types, t)
+	}
+	sort.Strings(types)
+	return types
+}
+
+// EventForType returns an empty struct matching the specified GitHub event type.
+// If messageType does not match any known event types, it returns nil.
+func EventForType(messageType string) interface{} {
+	prototype := eventTypeMapping[messageType]
+	if prototype == nil {
+		return nil
+	}
+	// return a _copy_ of the pointed-to-object.  Unfortunately, for this we
+	// need to use reflection.  If we store the actual objects in the map,
+	// we still need to use reflection to convert from `any` to the actual
+	// type, so this was deemed the lesser of two evils. (#2865)
+	return reflect.New(reflect.TypeOf(prototype).Elem()).Interface()
+}

github/messages_test.go

@@ -525,6 +525,23 @@ func TestParseWebHook(t *testing.T) {
 	}
 }
 
+func TestAllMessageTypesMapped(t *testing.T) {
+	for _, mt := range MessageTypes() {
+		if obj := EventForType(mt); obj == nil {
+			t.Errorf("messageMap missing message type %q", mt)
+		}
+	}
+}
+
+func TestUnknownMessageType(t *testing.T) {
+	if obj := EventForType("unknown"); obj != nil {
+		t.Errorf("EventForType(unknown) = %#v, want nil", obj)
+	}
+	if obj := EventForType(""); obj != nil {
+		t.Errorf(`EventForType("") = %#v, want nil`, obj)
+	}
+}
+
 func TestParseWebHook_BadMessageType(t *testing.T) {
 	if _, err := ParseWebHook("bogus message type", []byte("{}")); err == nil {
 		t.Fatal("ParseWebHook returned nil; wanted error")