feat: Pre-flight validate the entrypoint file exists

CHANGELOG.md

@@ -18,6 +18,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+- Deployments now fail early with a clear error if the entrypoint file does not exist. (#2964)
 - Log messages in the Publisher Logs panel are no longer duplicated when multiple deployments are made. (#3069)
 - Fix creating deployments of R Markdown documents that include parameters on Connect Cloud. (#3388)
 - The Publisher outputs (detailed logs) have been consolidated into one channel called "Posit Publisher". (#3168)

internal/clients/connect/capabilities.go

@@ -59,6 +59,37 @@ func checkRequirementsFile(base util.AbsolutePath, cfg *config.Config) error {
 	return nil
 }
 
+const entrypointFileMissing = `entrypoint file '%s' does not exist`
+
+type entrypointErrDetails struct {
+	Entrypoint string `json:"entrypoint"`
+}
+
+func checkEntrypoint(base util.AbsolutePath, cfg *config.Config) error {
+	// Module references (e.g., "app:myapp", "shiny.express.app:app_2e_py")
+	// are not file paths and should not be validated as files.
+	// Module references are currently constructed by reading the file so we
+	// already know the file exists at this point.
+	if strings.Contains(cfg.Entrypoint, ":") {
+		return nil
+	}
+
+	entrypointPath := base.Join(cfg.Entrypoint)
+	exists, err := entrypointPath.Exists()
+	if err != nil {
+		return err
+	}
+
+	if !exists {
+		return types.NewAgentError(
+			types.ErrorEntrypointNotFound,
+			fmt.Errorf(entrypointFileMissing, cfg.Entrypoint),
+			entrypointErrDetails{Entrypoint: cfg.Entrypoint},
+		)
+	}
+	return nil
+}
+
 func (c *ConnectClient) CheckCapabilities(base util.AbsolutePath, cfg *config.Config, contentID *types.ContentID, log logging.Logger) error {
 	if contentID != nil && *contentID != "" {
 		err := c.ValidateDeploymentTarget(*contentID, cfg, log)
@@ -72,6 +103,10 @@ func (c *ConnectClient) CheckCapabilities(base util.AbsolutePath, cfg *config.Co
 			return err
 		}
 	}
+	err := checkEntrypoint(base, cfg)
+	if err != nil {
+		return err
+	}
 	settings, err := c.GetSettings(base, cfg, log)
 	if err != nil {
 		return err

internal/clients/connect/capabilities_test.go

@@ -11,6 +11,7 @@ import (
 	"github.com/posit-dev/publisher/internal/clients/connect/server_settings"
 	"github.com/posit-dev/publisher/internal/config"
 	"github.com/posit-dev/publisher/internal/contenttypes"
+	"github.com/posit-dev/publisher/internal/util"
 	"github.com/posit-dev/publisher/internal/util/utiltest"
 )
 
@@ -307,3 +308,44 @@ func (s *CapabilitiesSuite) TestKubernetesGPULimits() {
 	s.ErrorContains(a.checkConfig(makeGPURequest(5, 0)), "amd_gpu_limit value of 5 is higher than configured maximum of 1 on this server")
 	s.ErrorContains(a.checkConfig(makeGPURequest(0, 5)), "nvidia_gpu_limit value of 5 is higher than configured maximum of 2 on this server")
 }
+
+func (s *CapabilitiesSuite) TestCheckEntrypointNotFound() {
+	base := util.NewAbsolutePath(s.T().TempDir(), nil)
+	cfg := &config.Config{
+		Entrypoint: "nonexistent.py",
+	}
+	err := checkEntrypoint(base, cfg)
+	s.Error(err)
+	s.ErrorContains(err, "entrypoint file 'nonexistent.py' does not exist")
+}
+
+func (s *CapabilitiesSuite) TestCheckEntrypointExists() {
+	base := util.NewAbsolutePath(s.T().TempDir(), nil)
+	// Create a temporary file to test against
+	entrypointFile := base.Join("app.py")
+	err := entrypointFile.WriteFile([]byte("# test app"), 0644)
+	s.NoError(err)
+
+	cfg := &config.Config{
+		Entrypoint: "app.py",
+	}
+	err = checkEntrypoint(base, cfg)
+	s.NoError(err)
+}
+
+func (s *CapabilitiesSuite) TestCheckEntrypointModuleReference() {
+	base := util.NewAbsolutePath(s.T().TempDir(), nil)
+	// Module references like "app:myapp" or "shiny.express.app:app_2e_py"
+	// should not be validated as file paths
+	cfg := &config.Config{
+		Entrypoint: "shiny.express.app:app_2e_py",
+	}
+	err := checkEntrypoint(base, cfg)
+	s.NoError(err)
+
+	cfg2 := &config.Config{
+		Entrypoint: "app:myapp",
+	}
+	err = checkEntrypoint(base, cfg2)
+	s.NoError(err)
+}

internal/types/error.go

@@ -38,6 +38,7 @@ const (
 	ErrorDeviceAuthSlowDown           ErrorCode = "deviceAuthSlowDown"
 	ErrorDeviceAuthAccessDenied       ErrorCode = "deviceAuthAccessDenied"
 	ErrorDeviceAuthExpiredToken       ErrorCode = "deviceAuthExpiredToken"
+	ErrorEntrypointNotFound           ErrorCode = "entrypointNotFound"
 )
 
 type EventableError interface {