Ensure frontend functions work when they don't return a value

.changeset/little-peas-roll.md

@@ -0,0 +1,7 @@
+---
+"@gradio/app": patch
+"@gradio/client": patch
+"gradio": patch
+---
+
+fix:Ensure frontend functions work when they don't return a value

client/js/src/helpers/api_info.ts

@@ -383,7 +383,7 @@ export function handle_message(
  */
 
 export const map_data_to_params = (
-	data: unknown[] | Record<string, unknown>,
+	data: unknown[] | Record<string, unknown> = [],
 	api_info: ApiInfo<JsApiData | ApiData>
 ): unknown[] => {
 	const parameters = Object.values(api_info.named_endpoints).flatMap(

client/js/src/test/api_info.test.ts

@@ -580,6 +580,20 @@ describe("map_data_params", () => {
 		expect(result).toEqual(data);
 	});
 
+	it("should return an empty array when data is an empty array", () => {
+		const data = [];
+
+		const result = map_data_to_params(data, transformed_api_info);
+		expect(result).toEqual(data);
+	});
+
+	it("should return an empty array when data is not defined", () => {
+		const data = undefined;
+
+		const result = map_data_to_params(data, transformed_api_info);
+		expect(result).toEqual([]);
+	});
+
 	it("should return the data when too many arguments are provided for the endpoint", () => {
 		const data = [1, 2, 3, 4];
 

demo/outbreak_forecast/run.ipynb

@@ -1 +1 @@
-{"cells": [{"cell_type": "markdown", "id": "302934307671667531413257853548643485645", "metadata": {}, "source": ["# Gradio Demo: outbreak_forecast\n", "### Generate a plot based on 5 inputs.\n", "        "]}, {"cell_type": "code", "execution_count": null, "id": "272996653310673477252411125948039410165", "metadata": {}, "outputs": [], "source": ["!pip install -q gradio numpy matplotlib bokeh plotly altair"]}, {"cell_type": "code", "execution_count": null, "id": "288918539441861185822528903084949547379", "metadata": {}, "outputs": [], "source": ["import altair\n", "\n", "import gradio as gr\n", "from math import sqrt\n", "import matplotlib.pyplot as plt\n", "import numpy as np\n", "import plotly.express as px\n", "import pandas as pd\n", "\n", "\n", "def outbreak(plot_type, r, month, countries, social_distancing):\n", "    months = [\"January\", \"February\", \"March\", \"April\", \"May\"]\n", "    m = months.index(month)\n", "    start_day = 30 * m\n", "    final_day = 30 * (m + 1)\n", "    x = np.arange(start_day, final_day + 1)\n", "    pop_count = {\"USA\": 350, \"Canada\": 40, \"Mexico\": 300, \"UK\": 120}\n", "    if social_distancing:\n", "        r = sqrt(r)\n", "    df = pd.DataFrame({\"day\": x})\n", "    for country in countries:\n", "        df[country] = x ** (r) * (pop_count[country] + 1)\n", "\n", "    if plot_type == \"Matplotlib\":\n", "        fig = plt.figure()\n", "        plt.plot(df[\"day\"], df[countries].to_numpy())\n", "        plt.title(\"Outbreak in \" + month)\n", "        plt.ylabel(\"Cases\")\n", "        plt.xlabel(\"Days since Day 0\")\n", "        plt.legend(countries)\n", "        return fig\n", "    elif plot_type == \"Plotly\":\n", "        fig = px.line(df, x=\"day\", y=countries)\n", "        fig.update_layout(\n", "            title=\"Outbreak in \" + month,\n", "            xaxis_title=\"Cases\",\n", "            yaxis_title=\"Days Since Day 0\",\n", "        )\n", "        return fig\n", "    elif plot_type == \"Altair\":\n", "        df = df.melt(id_vars=\"day\").rename(columns={\"variable\": \"country\"})\n", "        fig = altair.Chart(df).mark_line().encode(x=\"day\", y='value', color='country')\n", "        return fig\n", "    else:\n", "        raise ValueError(\"A plot type must be selected\")\n", "\n", "\n", "inputs = [\n", "    gr.Dropdown([\"Matplotlib\", \"Plotly\", \"Altair\"], label=\"Plot Type\"),\n", "    gr.Slider(1, 4, 3.2, label=\"R\"),\n", "    gr.Dropdown([\"January\", \"February\", \"March\", \"April\", \"May\"], label=\"Month\"),\n", "    gr.CheckboxGroup(\n", "        [\"USA\", \"Canada\", \"Mexico\", \"UK\"], label=\"Countries\", value=[\"USA\", \"Canada\"]\n", "    ),\n", "    gr.Checkbox(label=\"Social Distancing?\"),\n", "]\n", "outputs = gr.Plot()\n", "\n", "demo = gr.Interface(\n", "    fn=outbreak,\n", "    inputs=inputs,\n", "    outputs=outputs,\n", "    examples=[\n", "        [\"Matplotlib\", 2, \"March\", [\"Mexico\", \"UK\"], True],\n", "        [\"Altair\", 2, \"March\", [\"Mexico\", \"Canada\"], True],\n", "        [\"Plotly\", 3.6, \"February\", [\"Canada\", \"Mexico\", \"UK\"], False],\n", "    ],\n", "    cache_examples=True,\n", ")\n", "\n", "if __name__ == \"__main__\":\n", "    demo.launch()\n", "\n", "\n", "\n"]}], "metadata": {}, "nbformat": 4, "nbformat_minor": 5}
+{"cells": [{"cell_type": "markdown", "id": "302934307671667531413257853548643485645", "metadata": {}, "source": ["# Gradio Demo: outbreak_forecast\n", "### Generate a plot based on 5 inputs.\n", "        "]}, {"cell_type": "code", "execution_count": null, "id": "272996653310673477252411125948039410165", "metadata": {}, "outputs": [], "source": ["!pip install -q gradio numpy matplotlib bokeh plotly altair"]}, {"cell_type": "code", "execution_count": null, "id": "288918539441861185822528903084949547379", "metadata": {}, "outputs": [], "source": ["import altair\n", "\n", "import gradio as gr\n", "from math import sqrt\n", "import matplotlib.pyplot as plt\n", "import numpy as np\n", "import plotly.express as px\n", "import pandas as pd\n", "\n", "\n", "def outbreak(plot_type, r, month, countries, social_distancing):\n", "    months = [\"January\", \"February\", \"March\", \"April\", \"May\"]\n", "    m = months.index(month)\n", "    start_day = 30 * m\n", "    final_day = 30 * (m + 1)\n", "    x = np.arange(start_day, final_day + 1)\n", "    pop_count = {\"USA\": 350, \"Canada\": 40, \"Mexico\": 300, \"UK\": 120}\n", "    if social_distancing:\n", "        r = sqrt(r)\n", "    df = pd.DataFrame({\"day\": x})\n", "    for country in countries:\n", "        df[country] = x ** (r) * (pop_count[country] + 1)\n", "\n", "    if plot_type == \"Matplotlib\":\n", "        fig = plt.figure()\n", "        plt.plot(df[\"day\"], df[countries].to_numpy())\n", "        plt.title(\"Outbreak in \" + month)\n", "        plt.ylabel(\"Cases\")\n", "        plt.xlabel(\"Days since Day 0\")\n", "        plt.legend(countries)\n", "        return fig\n", "    elif plot_type == \"Plotly\":\n", "        fig = px.line(df, x=\"day\", y=countries)\n", "        fig.update_layout(\n", "            title=\"Outbreak in \" + month,\n", "            xaxis_title=\"Cases\",\n", "            yaxis_title=\"Days Since Day 0\",\n", "        )\n", "        return fig\n", "    elif plot_type == \"Altair\":\n", "        df = df.melt(id_vars=\"day\").rename(columns={\"variable\": \"country\"})\n", "        fig = altair.Chart(df).mark_line().encode(x=\"day\", y=\"value\", color=\"country\")\n", "        return fig\n", "    else:\n", "        raise ValueError(\"A plot type must be selected\")\n", "\n", "\n", "inputs = [\n", "    gr.Dropdown([\"Matplotlib\", \"Plotly\", \"Altair\"], label=\"Plot Type\"),\n", "    gr.Slider(1, 4, 3.2, label=\"R\"),\n", "    gr.Dropdown([\"January\", \"February\", \"March\", \"April\", \"May\"], label=\"Month\"),\n", "    gr.CheckboxGroup(\n", "        [\"USA\", \"Canada\", \"Mexico\", \"UK\"], label=\"Countries\", value=[\"USA\", \"Canada\"]\n", "    ),\n", "    gr.Checkbox(label=\"Social Distancing?\"),\n", "]\n", "outputs = gr.Plot()\n", "\n", "demo = gr.Interface(\n", "    fn=outbreak,\n", "    inputs=inputs,\n", "    outputs=outputs,\n", "    examples=[\n", "        [\"Matplotlib\", 2, \"March\", [\"Mexico\", \"UK\"], True],\n", "        [\"Altair\", 2, \"March\", [\"Mexico\", \"Canada\"], True],\n", "        [\"Plotly\", 3.6, \"February\", [\"Canada\", \"Mexico\", \"UK\"], False],\n", "    ],\n", "    cache_examples=True,\n", ")\n", "\n", "if __name__ == \"__main__\":\n", "    demo.launch()\n"]}], "metadata": {}, "nbformat": 4, "nbformat_minor": 5}

demo/outbreak_forecast/run.py

@@ -39,7 +39,7 @@ def outbreak(plot_type, r, month, countries, social_distancing):
         return fig
     elif plot_type == "Altair":
         df = df.melt(id_vars="day").rename(columns={"variable": "country"})
-        fig = altair.Chart(df).mark_line().encode(x="day", y='value', color='country')
+        fig = altair.Chart(df).mark_line().encode(x="day", y="value", color="country")
         return fig
     else:
         raise ValueError("A plot type must be selected")
@@ -70,6 +70,3 @@ def outbreak(plot_type, r, month, countries, social_distancing):
 
 if __name__ == "__main__":
     demo.launch()
-
-
-

js/app/src/init.ts

@@ -370,6 +370,7 @@ export function process_frontend_fn(
 		return new AsyncFunction(
 			"__fn_args",
 			`  let result = await (${source})(...__fn_args);
+  if (typeof result === "undefined") return [];
   return (${wrap} && !Array.isArray(result)) ? [result] : result;`
 		);
 	} catch (e) {