update

app.py

@@ -212,7 +212,7 @@ update_js = """
 """
 
 with gr.Blocks() as demo:
-	stage1_json = gr.JSON(visible=False)
+	stage1_json = gr.JSON({}, visible=False)
 	stage2_json = gr.JSON(visible=False)
 	channel_json = gr.JSON(visible=False)
 
@@ -289,6 +289,11 @@ with gr.Blocks() as demo:
 	# |                                Stage1: channel mapping                                 |
 	# +========================================================================================+
 	def reset_all(stage1_info, stage2_info, in_loc):
+		if in_loc == None:
+			gr.Warning("Please upload a file.")
+			stage1_info["errorFlag"] = True
+			return {stage1_json : stage1_info}
+	    
 		# stop Stage2
 		if stage2_info!=None and stage2_info["state"]=="running":
 			utils.dataDelete(stage2_info["filePath"])
@@ -314,6 +319,7 @@ with gr.Blocks() as demo:
 		    	"outputResult" : rootpath+'/'+stage1_id+'/'+outputname
 			},
 			"state" : "step1-initializing",
+			"errorFlag" : False,
 	    	"step2" : {
 	    		"count" : None,
 				"totalNum" : None
@@ -365,10 +371,13 @@ with gr.Blocks() as demo:
 	# |                                    step transition                                     |
 	# +========================================================================================+
 	def init_next_step(stage1_info, channel_info, fillmode, sel_radio, sel_chkbox):
+		if stage1_info["errorFlag"] == True:
+			stage1_info["errorFlag"] = False
+			yield {stage1_json : stage1_info}
 		
 		# ========================================step0=========================================
 		# step0 to step1
-		if stage1_info["state"] == "step1-initializing":
+		elif stage1_info["state"] == "step1-initializing":
 			yield {desc_md : gr.Markdown("Mapping...", visible=True)}
 		    
 			# match the names