fix(actions): reject workflow_dispatch for workflows without that trigger (#37660)

## Summary

Fixes #37528

This PR makes the workflow dispatch API reject workflows that do not
declare `workflow_dispatch`. Previously, `POST
/repos/{owner}/{repo}/actions/workflows/{workflow_id}/dispatches` could
create an `ActionRun` for a workflow that only declared another event
such as `push`.

The service now validates that the target workflow has a
`workflow_dispatch` trigger before inserting the run. The API maps that
validation failure to `422 Unprocessable Entity`, matching existing
validation failures in this handler.

The regression test creates a push-only workflow, dispatches it through
the public API, asserts the `workflow_dispatch` validation message, and
verifies that no run was inserted.

## Disclosure

Developed with assistance from OpenAI Codex.

---------

Co-authored-by: Nicolas <bircni@icloud.com>

routers/api/v1/repo/action.go

@@ -1091,6 +1091,8 @@ func ActionsDispatchWorkflow(ctx *context.APIContext) {
 			ctx.APIError(http.StatusNotFound, err)
 		} else if errors.Is(err, util.ErrPermissionDenied) {
 			ctx.APIError(http.StatusForbidden, err)
+		} else if errors.Is(err, util.ErrInvalidArgument) {
+			ctx.APIError(http.StatusUnprocessableEntity, err)
 		} else {
 			ctx.APIErrorInternal(err)
 		}

services/actions/workflow.go

@@ -140,11 +140,17 @@ func DispatchActionWorkflow(ctx reqctx.RequestContext, doer *user_model.User, re
 	workflow := &model.Workflow{
 		RawOn: singleWorkflow.RawOn,
 	}
+	workflowDispatch := workflow.WorkflowDispatchConfig()
+	if workflowDispatch == nil {
+		return 0, util.ErrorWrapTranslatable(
+			util.NewInvalidArgumentErrorf("workflow %q has no workflow_dispatch event trigger", workflowID),
+			"actions.workflow.has_no_workflow_dispatch", workflowID,
+		)
+	}
+
 	inputsWithDefaults := make(map[string]any)
-	if workflowDispatch := workflow.WorkflowDispatchConfig(); workflowDispatch != nil {
+	if err = processInputs(workflowDispatch, inputsWithDefaults); err != nil {
-		if err = processInputs(workflowDispatch, inputsWithDefaults); err != nil {
+		return 0, err
-			return 0, err
-		}
 	}
 
 	// ctx.Req.PostForm -> WorkflowDispatchPayload.Inputs -> ActionRun.EventPayload -> runner: ghc.Event

tests/integration/actions_trigger_test.go

@@ -931,6 +931,76 @@ jobs:
 	})
 }
 
+func TestWorkflowDispatchPublicApiRequiresWorkflowDispatchTrigger(t *testing.T) {
+	onGiteaRun(t, func(t *testing.T, u *url.URL) {
+		user2 := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: 2})
+		session := loginUser(t, user2.Name)
+		token := getTokenForLoggedInUser(t, session, auth_model.AccessTokenScopeWriteRepository)
+
+		repo, err := repo_service.CreateRepository(t.Context(), user2, user2, repo_service.CreateRepoOptions{
+			Name:          "workflow-dispatch-requires-trigger",
+			Description:   "test workflow dispatch requires workflow_dispatch",
+			AutoInit:      true,
+			Gitignores:    "Go",
+			License:       "MIT",
+			Readme:        "Default",
+			DefaultBranch: "main",
+			IsPrivate:     false,
+		})
+		require.NoError(t, err)
+		require.NotNil(t, repo)
+
+		addWorkflowToBaseResp, err := files_service.ChangeRepoFiles(t.Context(), repo, user2, &files_service.ChangeRepoFilesOptions{
+			Files: []*files_service.ChangeRepoFile{
+				{
+					Operation: "create",
+					TreePath:  ".gitea/workflows/push-only.yml",
+					ContentReader: strings.NewReader(`
+on:
+  push:
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - run: echo helloworld
+`),
+				},
+			},
+			Message:   "add workflow",
+			OldBranch: "main",
+			NewBranch: "main",
+			Author: &files_service.IdentityOptions{
+				GitUserName:  user2.Name,
+				GitUserEmail: user2.Email,
+			},
+			Committer: &files_service.IdentityOptions{
+				GitUserName:  user2.Name,
+				GitUserEmail: user2.Email,
+			},
+			Dates: &files_service.CommitDateOptions{
+				Author:    time.Now(),
+				Committer: time.Now(),
+			},
+		})
+		require.NoError(t, err)
+		require.NotNil(t, addWorkflowToBaseResp)
+
+		values := url.Values{}
+		values.Set("ref", "main")
+		req := NewRequestWithURLValues(t, "POST", fmt.Sprintf("/api/v1/repos/%s/actions/workflows/push-only.yml/dispatches", repo.FullName()), values).
+			AddTokenAuth(token)
+		resp := MakeRequest(t, req, http.StatusUnprocessableEntity)
+		apiError := DecodeJSON(t, resp, &api.APIError{})
+		assert.Contains(t, apiError.Message, "has no workflow_dispatch event trigger")
+
+		unittest.AssertNotExistsBean(t, &actions_model.ActionRun{
+			RepoID:     repo.ID,
+			Event:      "workflow_dispatch",
+			WorkflowID: "push-only.yml",
+		})
+	})
+}
+
 func TestWorkflowDispatchPublicApiWithInputs(t *testing.T) {
 	onGiteaRun(t, func(t *testing.T, u *url.URL) {
 		user2 := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: 2})