Replace error message matching with structural error checks in apps dev and DBFS filer

cmd/apps/dev.go

@@ -12,7 +12,6 @@ import (
 	"os/exec"
 	"os/signal"
 	"strconv"
-	"strings"
 	"syscall"
 	"time"
 
@@ -22,6 +21,7 @@ import (
 	"github.com/databricks/cli/libs/apps/vite"
 	"github.com/databricks/cli/libs/cmdctx"
 	"github.com/databricks/cli/libs/cmdio"
+	"github.com/databricks/databricks-sdk-go/apierr"
 	"github.com/spf13/cobra"
 )
 
@@ -40,6 +40,12 @@ func isViteReady(port int) bool {
 	return true
 }
 
+// isAppNotFound reports whether err is the Apps API's 404, which covers both a
+// never-created and a deleted app.
+func isAppNotFound(err error) bool {
+	return errors.Is(err, apierr.ErrNotFound)
+}
+
 // detectAppNameFromBundle tries to extract the app name from a databricks.yml bundle config.
 // Returns the app name if found, or empty string if no bundle or no apps found.
 // This properly loads and initializes the bundle to resolve variables and apply prefixes.
@@ -184,7 +190,7 @@ Examples:
 				return domainErr
 			})
 			if err != nil {
-				if strings.Contains(err.Error(), "does not exist") || strings.Contains(err.Error(), "is deleted") {
+				if isAppNotFound(err) {
 					return fmt.Errorf("application '%s' has not been deployed yet. Run `databricks apps deploy` to deploy and then try again", appName)
 				}
 				return fmt.Errorf("failed to get app domain: %w", err)

cmd/apps/dev_test.go

@@ -1,13 +1,16 @@
 package apps
 
 import (
+	"errors"
+	"fmt"
 	"net"
 	"os"
 	"testing"
 	"time"
 
 	"github.com/databricks/cli/libs/apps/vite"
 	"github.com/databricks/cli/libs/cmdio"
+	"github.com/databricks/databricks-sdk-go/apierr"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
@@ -44,6 +47,24 @@ func TestIsViteReady(t *testing.T) {
 	})
 }
 
+func TestIsAppNotFound(t *testing.T) {
+	notFound := &apierr.APIError{
+		StatusCode: 404,
+		ErrorCode:  "NOT_FOUND",
+		Message:    "App with name test-app does not exist or is deleted.",
+	}
+	assert.True(t, isAppNotFound(notFound))
+	assert.True(t, isAppNotFound(fmt.Errorf("failed to get app: %w", notFound)))
+
+	forbidden := &apierr.APIError{
+		StatusCode: 403,
+		ErrorCode:  "PERMISSION_DENIED",
+		Message:    "user does not have permission",
+	}
+	assert.False(t, isAppNotFound(forbidden))
+	assert.False(t, isAppNotFound(errors.New("app URL is empty")))
+}
+
 func TestViteServerScriptContent(t *testing.T) {
 	// Verify the embedded script is not empty
 	assert.NotEmpty(t, vite.ServerScript)

libs/filer/dbfs_client.go

@@ -148,13 +148,13 @@ func (w *DbfsClient) Read(ctx context.Context, name string) (io.ReadCloser, erro
 
 	handle, err := w.workspaceClient.Dbfs.Open(ctx, absPath, files.FileModeRead)
 	if err != nil {
-		// Return error if file is a directory
-		if strings.Contains(err.Error(), "cannot open directory for reading") {
-			return nil, notAFile{absPath}
-		}
-
 		aerr, ok := errors.AsType[*apierr.APIError](err)
 		if !ok {
+			// The SDK's Open fails with a client-side error carrying no sentinel
+			// when the path is a directory, so re-stat to detect that case.
+			if info, serr := w.workspaceClient.Dbfs.GetStatusByPath(ctx, absPath); serr == nil && info.IsDir {
+				return nil, notAFile{absPath}
+			}
 			return nil, err
 		}
 

libs/filer/dbfs_client_test.go

@@ -0,0 +1,54 @@
+package filer
+
+import (
+	"io/fs"
+	"testing"
+
+	"github.com/databricks/cli/libs/testserver"
+	"github.com/databricks/databricks-sdk-go"
+	"github.com/databricks/databricks-sdk-go/service/files"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func dbfsReadWithGetStatusResponse(t *testing.T, response any) error {
+	t.Helper()
+
+	server := testserver.New(t)
+	server.Handle("GET", "/api/2.0/dbfs/get-status", func(req testserver.Request) any {
+		return response
+	})
+	testserver.AddDefaultHandlers(server)
+
+	client, err := databricks.NewWorkspaceClient(&databricks.Config{
+		Host:  server.URL,
+		Token: "testtoken",
+	})
+	require.NoError(t, err)
+
+	f, err := NewDbfsClient(client, "/test")
+	require.NoError(t, err)
+
+	_, err = f.Read(t.Context(), "file")
+	require.Error(t, err)
+	return err
+}
+
+func TestDbfsClientReadDirectory(t *testing.T) {
+	err := dbfsReadWithGetStatusResponse(t, files.FileInfo{
+		Path:  "/test/file",
+		IsDir: true,
+	})
+	assert.ErrorIs(t, err, fs.ErrInvalid)
+}
+
+func TestDbfsClientReadFileDoesNotExist(t *testing.T) {
+	err := dbfsReadWithGetStatusResponse(t, testserver.Response{
+		StatusCode: 404,
+		Body: map[string]string{
+			"error_code": "RESOURCE_DOES_NOT_EXIST",
+			"message":    "test error",
+		},
+	})
+	assert.ErrorIs(t, err, fs.ErrNotExist)
+}