Export DataPipes through the backend writer and remove FileId

+io/+backend/+base/Writer.m

@@ -16,10 +16,6 @@
         ObjectIdToPathMap
     end
 
-    properties (Dependent, SetAccess = private, Hidden)
-        FileId
-    end
-
     methods
         function obj = Writer(filename)
             if nargin < 1
@@ -109,6 +105,32 @@ function copyDatasetFromFile(obj, sourceFilename, sourcePath, destinationPath) %
             io.backend.base.Writer.throwNotImplemented("copyDatasetFromFile")
         end
 
+        function writtenPipe = exportDataPipe(obj, dataPipe, destinationPath) %#ok<INUSD>
+        % exportDataPipe - Write a DataPipe's dataset into this file.
+        %
+        % Writes the dataset held by dataPipe at destinationPath, honouring
+        % the pipe's storage configuration (chunking, compression and the
+        % other pipe properties). Returns the pipe state representing the
+        % dataset as written; DataPipe.export stores it as the pipe's new
+        % internal state, which is how an in-memory blueprint pipe becomes
+        % bound to the dataset in this file. A pipe already bound to a
+        % dataset in this file is left in place. A pipe bound to a dataset
+        % in a different file holds only a reference to that data, not the
+        % data itself, so exporting it raises an error
+        % ('NWB:BoundPipe:CannotExportToNewFile').
+        %
+        % Input Arguments:
+        %   obj - Writer instance targeting the destination file.
+        %   dataPipe - types.untyped.DataPipe whose dataset is written.
+        %   destinationPath - Path the dataset is written to in this file.
+        %
+        % Output Arguments:
+        %   writtenPipe - Pipe object bound to the dataset as written.
+
+            writtenPipe = [];
+            io.backend.base.Writer.throwNotImplemented("exportDataPipe")
+        end
+
         function writeSoftLink(obj, linkPath, targetPath) %#ok<INUSD>
             % writeSoftLink - Create a link to another location in this file.
             %
@@ -186,10 +208,6 @@ function close(obj) %#ok<MANU>
         function abort(obj)
             obj.close();
         end
-
-        function fileId = get.FileId(obj)
-            fileId = obj.getFileId();
-        end
     end
 
     methods (Static)
@@ -203,13 +221,6 @@ function abort(obj)
         end
     end
 
-    methods (Access = protected)
-        function fileId = getFileId(obj) %#ok<MANU>
-            io.backend.base.Writer.throwNotImplemented("getFileId")
-            fileId = [];
-        end
-    end
-
     methods (Static, Access = private)
         function throwNotImplemented(methodName)
             error("NWB:Backend:Writer:NotImplemented", ...

+io/+backend/+hdf5/HDF5Writer.m

@@ -136,6 +136,15 @@ function copyDatasetFromFile(obj, sourceFilename, sourcePath, destinationPath)
             H5F.close(src_fid);
         end
 
+        function writtenPipe = exportDataPipe(obj, dataPipe, destinationPath)
+            % The pipe internals (BoundPipe/BlueprintPipe) drive H5P/H5D
+            % directly for chunking, compression, dynamic filters and
+            % extendable datasets, so they legitimately consume a raw HDF5
+            % file id. Keeping this call inside the HDF5 writer means the
+            % raw id never crosses the backend interface.
+            writtenPipe = dataPipe.internal.write(obj.H5FileId, destinationPath);
+        end
+
         function writeSoftLink(obj, linkPath, targetPath)
             io.internal.h5.writeLink(obj.H5FileId, linkPath, "soft", targetPath);
         end
@@ -168,11 +177,6 @@ function deleteGroup(obj, groupPath)
         end
     end
 
-    methods (Access = protected)
-        function fileId = getFileId(obj)
-            fileId = obj.H5FileId;
-        end
-    end
 end
 
 function hasReference = isCompoundWithReference(src_tid)

+tests/+unit/+io/+backend/+base/BaseWriterTest.m

@@ -12,6 +12,7 @@
             "writeExternalLink", ...
             "validateReferenceResolvable", ...
             "copyDatasetFromFile", ...
+            "exportDataPipe", ...
             "getEmbeddedSpecLocation", ...
             "listChildGroupNames", ...
             "registerWrittenObjectId", ...

+tests/+unit/+io/+backend/HDF5WriterTest.m

@@ -15,7 +15,7 @@ function deleteGroupDeletesPopulatedGroup(testCase)
 
             writer.deleteGroup('/specifications/core');
 
-            groupExists = H5L.exists(writer.FileId, ...
+            groupExists = H5L.exists(writer.H5FileId, ...
                 '/specifications/core', 'H5P_DEFAULT');
             testCase.verifyFalse(logical(groupExists));
         end

+types/+untyped/DataPipe.m

@@ -270,7 +270,7 @@
 
         function refs = export(obj, writer, fullpath, refs)
             writer = io.backend.base.Writer.ensure(writer);
-            obj.internal = obj.internal.write(writer.FileId, fullpath);
+            obj.internal = writer.exportDataPipe(obj, fullpath);
         end
 
         %% Display