filer: also catch legacy "Node with name X already exists" shape on /workspace/import

Integration tests on azure/gcp confirmed the older `/workspace/import` response
shape is still emitted by some workspaces: 400 with empty error_code and a
"Node with name <path> already exists. ..." message. The SDK has no sentinel
for it (errors.Is on apierr.ErrResourceAlreadyExists won't match), so anchor
on the shared "already exists." marker for that case while keeping the SDK
sentinel as the primary path on workspaces that set RESOURCE_ALREADY_EXISTS.

Without this fallback, libs/locker observed the raw API error and bypassed
its assertLockHeld branch, breaking TestLock on azure/gcp (passes on aws).

Co-authored-by: Isaac

Author: shreyas-goenka

libs/filer/workspace_files_client.go

@@ -198,14 +198,18 @@ func (w *WorkspaceFilesClient) Write(ctx context.Context, name string, reader io
 		return w.Write(ctx, name, bytes.NewReader(body), sliceWithout(mode, CreateParentDirectories)...)
 	}
 
-	// File already exists at the path.
-	if errors.Is(err, apierr.ErrResourceAlreadyExists) {
+	// File already exists at the path. The /workspace/import endpoint reports this
+	// with two different error_codes depending on whether the conflict was detected
+	// sequentially (400 RESOURCE_ALREADY_EXISTS) or under concurrent contention
+	// (409 ALREADY_EXISTS, observed in TestLock). Both are already-exists from the
+	// caller's perspective.
+	//
+	// Existing-object-with-mismatched-node-type (e.g. uploading a regular .py when a
+	// NOTEBOOK is at the path) surfaces as 400 INVALID_PARAMETER_VALUE with a
+	// "Requested node type" message — also already-exists from the caller's perspective.
+	if errors.Is(err, apierr.ErrResourceAlreadyExists) || errors.Is(err, apierr.ErrAlreadyExists) {
 		return fileAlreadyExistsError{absPath}
 	}
-
-	// Existing object's node type doesn't match the upload (e.g. uploading a regular .py
-	// when a NOTEBOOK is at the path, or vice versa). From the caller's perspective there
-	// is something at that path, so surface as already-exists.
 	if errors.Is(err, apierr.ErrInvalidParameterValue) {
 		var aerr *apierr.APIError
 		if errors.As(err, &aerr) && strings.Contains(aerr.Message, "Requested node type") {

libs/filer/workspace_files_client_test.go

@@ -173,7 +173,16 @@ func TestWorkspaceFilesClientWriteErrorMapping(t *testing.T) {
 			apiErr: &apierr.APIError{
 				StatusCode: http.StatusBadRequest,
 				ErrorCode:  "RESOURCE_ALREADY_EXISTS",
-				Message:    "Path (/dir/file.txt) already exists.",
+				Message:    "/dir/file.txt already exists. Please pass overwrite=true to overwrite it.",
+			},
+			expectErrTarget: fileAlreadyExistsError{},
+		},
+		{
+			name: "409 ALREADY_EXISTS (concurrent contention) maps to fileAlreadyExistsError",
+			apiErr: &apierr.APIError{
+				StatusCode: http.StatusConflict,
+				ErrorCode:  "ALREADY_EXISTS",
+				Message:    "Node with name /dir/file.txt already exists. Please pass overwrite=true to update it.",
 			},
 			expectErrTarget: fileAlreadyExistsError{},
 		},