Show explicit error message for SSSP run over a graph with no edge we…

…ight (#2929)

Fixes #1878

Signed-off-by: wang <jiede.wl@alibaba-inc.com>

python/graphscope/analytical/app/sssp.py

@@ -19,6 +19,8 @@
 from graphscope.framework.app import AppAssets
 from graphscope.framework.app import not_compatible_for
 from graphscope.framework.app import project_to_simple
+from graphscope.framework.graph import GraphDAGNode
+from graphscope.proto import graph_def_pb2
 
 __all__ = [
     "sssp",
@@ -59,4 +61,15 @@ def sssp(graph, src=0, weight=None):
         >>> c = graphscope.sssp(pg, src=6)
         >>> sess.close()
     """
+    if not isinstance(graph, GraphDAGNode):
+        if graph.schema.edata_type == graph_def_pb2.NULLVALUE:
+            raise RuntimeError(
+                "The edge data is empty, and the edge data type should be integers or "
+                "floating point numbers to run SSSP. Suggest to use bfs() algorithm."
+            )
+        if graph.schema.edata_type == graph_def_pb2.STRING:
+            raise RuntimeError(
+                "The edge data type is string, and the edge data type should be "
+                "integers or floating point numbers to run SSSP."
+            )
     return AppAssets(algo="sssp", context="vertex_data")(graph, src)