Add intermediate previews and graph reconnection

src/govoplan_dataflow/backend/service.py

@@ -567,6 +567,7 @@ def preview_pipeline(
                 truncated=False,
                 diagnostics=validated.diagnostics,
                 node_diagnostics=[],
+                node_preview=None,
                 source_fingerprints=[],
                 input_row_count=0,
                 definition_hash="",
@@ -622,6 +623,7 @@ def preview_pipeline(
             graph,
             row_limit=payload.row_limit,
             source_resolver=resolve_source,
+            preview_node_id=payload.preview_node_id,
         )
         status = "succeeded"
         error = None
@@ -631,6 +633,7 @@ def preview_pipeline(
         total_rows = result.total_rows
         truncated = result.truncated
         node_diagnostics = result.node_diagnostics
+        node_preview = result.node_preview
         source_fingerprints = result.source_fingerprints
         input_row_count = result.input_row_count
     except PipelineExecutionError as exc:
@@ -650,6 +653,7 @@ def preview_pipeline(
         total_rows = 0
         truncated = False
         node_diagnostics = list(exc.node_diagnostics)
+        node_preview = exc.node_preview
         source_fingerprints = list(exc.source_fingerprints)
         input_row_count = exc.input_row_count
 
@@ -686,6 +690,7 @@ def preview_pipeline(
         truncated=truncated,
         diagnostics=diagnostics,
         node_diagnostics=node_diagnostics,
+        node_preview=node_preview,
         source_fingerprints=source_fingerprints,
         input_row_count=input_row_count,
         definition_hash=graph_hash,