filer: also catch 409 ALREADY_EXISTS on /workspace/import (concurrent writes)

The /workspace/import endpoint reports an existing path with two different
error codes depending on contention:

  - 400 RESOURCE_ALREADY_EXISTS: sequential conflict (overwrite=false on existing path)
    Message: "<path> already exists. Please pass overwrite=true to overwrite it."

  - 409 ALREADY_EXISTS: concurrent contention (e.g. multiple deploy locks racing)
    Message: "Node with name <path> already exists. Please pass overwrite=true to update it."

Verified by direct probe against aws-prod and aws-prod-ucws — sequential
conflicts produce the first shape, but a 5-goroutine race on the same path
produces the second shape with status 409 and error_code ALREADY_EXISTS.

The original PR's errors.Is(err, ErrResourceAlreadyExists) only catches the
first shape, leaving locker.Lock() returning the raw API error instead of
falling through to assertLockHeld() — which is what TestLock asserts. Add
errors.Is(err, ErrAlreadyExists) for the second shape; both inherit from
apierr.ErrResourceConflict but we use the specific sentinels rather than
the broader parent (ErrResourceConflict also covers ErrAborted, which is
a different concept).

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{},
 		},