Flutter调用Supabase Edge函数删用户遇FormatException求助

调用Supabase Edge函数删除用户时遭遇FormatException，错误信息如下：

FormatException: Unexpected character (at character 1) <!DOCTYPE html>

触发错误的Flutter代码片段 #

Future<void> handlingUserDeletion() async {
  try {
    await supabase.functions.invoke(
      "delete-user",
      headers: {
        'Authorization': 'Bearer ${supabase.auth.currentSession?.accessToken}'
      },
    );
    if (mounted) {
      supabase.auth.signOut();
    }
  } on PostgrestException catch (error) {
    debugPrint(error.message);
  } catch (e) {
    debugPrint(e.toString());
  }
}

Supabase Edge函数（delete-user）代码 #

import { serve } from 'https://deno.land/std@0.182.0/http/server.ts';
import { createClient } from 'https://esm.sh/@supabase/supabase-js@2.14.0';
import { corsHeaders } from '../_shared/cors.ts';

console.log("Delete user account function");

serve(async (request) => {

  // This is needed if you're planning to invoke your function from a browser.
  if (request.method === 'OPTIONS') {
    return new Response('ok', { headers: corsHeaders })
  }

  try {
    //Create instance of SupabaseClient
    const supabaseClient = createClient(
      Deno.env.get('SUPABASE_URL') ?? '',
      Deno.env.get('SUPABASE_SERVICE_ROLE_KEY') ?? '',
      { global: { headers: { Authorization: request.headers.get('Authorization')! } } }
    );

    // Create a user object which contains the data we need to identify the user.id
    const {
      data: { user },
    } = await supabaseClient.auth.getUser()

    // Throw an error if there are any issues with identifying the users from the token
    if (!user) throw new Error('No user found for JWT!');
  
    // Create supabaseAdmin client which specifically uses the Service Role
    // Key in order to perform elavated administration actins
    const supabaseAdmin = createClient(
      Deno.env.get('SUPABASE_URL') ?? '',
      Deno.env.get('SUPABASE_SERVICE_ROLE_KEY') ?? ''
    )

    // Call the deleteUser method on the supabaseAdmin client and pass the user.id
    const { data: deletion_data, error: deletion_error } = await supabaseAdmin.auth.admin.deleteUser(user.id, true);
    
    // Log deletion error so we can debug. Delete if not required! 
    // console.log(deletion_error);
    if (deletion_error) throw deletion_error;

    // Return a response of the user which has been deleted
    return new Response("User deleted: " + JSON.stringify(deletion_data, null, 2), {
      headers: { ...corsHeaders, 'Content-Type': 'application/json' },
      status: 200,
    });
  } catch (error) {
    // Return an error with the error message should it run in to any issues
    return new Response(JSON.stringify({ error: error.message }), {
      headers: { ...corsHeaders, 'Content-Type': 'application/json' },
      status: 400,
    })
  }
});

cors.ts文件代码 #

export const corsHeaders = {
    'Access-Control-Allow-Origin': '*',
    'Access-Control-Allow-Headers': 'authorization, x-client-info, apikey, content-type',
}

版本信息 #

• Flutter 3.10.6
• supabase_flutter: ^1.8.1

异常原因分析 #

这个FormatException说明Flutter客户端接收到的响应不是合法的JSON格式，而是HTML内容。通常是Edge函数执行出错后，Supabase返回了默认的错误页面（HTML格式），而非函数本身定义的JSON错误响应。可能的触发点包括：

1. Edge函数的成功响应格式不合法，返回了非纯JSON内容
2. 环境变量未正确配置，导致Supabase客户端初始化失败
3. 请求的Authorization令牌为空或无效，导致函数内部抛出未被正确处理的错误
4. 函数内部的非空断言触发运行时错误，未进入catch块返回JSON响应

可行解决办法 #

1. 修正Edge函数的响应格式
   成功响应中，不要在JSON前拼接字符串"User deleted: "，因为Content-Type设为application/json，必须返回纯JSON内容。修改成功响应代码：

   return new Response(JSON.stringify({ 
     message: "User deleted",
     data: deletion_data 
   }, null, 2), {
     headers: { ...corsHeaders, 'Content-Type': 'application/json' },
     status: 200,
   });
   

2. 检查并确保环境变量正确配置
   在Supabase控制台的Edge函数设置中，确认SUPABASE_URL和SUPABASE_SERVICE_ROLE_KEY已正确添加，且值不为空。函数中可以添加空值检查，提前抛出明确错误：

   const supabaseUrl = Deno.env.get('SUPABASE_URL');
   const serviceRoleKey = Deno.env.get('SUPABASE_SERVICE_ROLE_KEY');
   if (!supabaseUrl || !serviceRoleKey) {
     throw new Error('Missing Supabase environment variables');
   }
   

3. 处理Authorization头为空的情况

   • Flutter端：调用函数前先检查当前会话是否存在，避免发送空令牌：

     final session = supabase.auth.currentSession;
     if (session == null) {
       debugPrint('No active session');
       return;
     }
     await supabase.functions.invoke(
       "delete-user",
       headers: {
         'Authorization': 'Bearer ${session.accessToken}'
       },
     );
     

   • Edge函数端：移除非空断言，先检查Authorization头是否存在：

     const authHeader = request.headers.get('Authorization');
     if (!authHeader) {
       throw new Error('Authorization header missing');
     }
     const supabaseClient = createClient(
       supabaseUrl,
       serviceRoleKey,
       { global: { headers: { Authorization: authHeader } } }
     );
     

4. 查看Edge函数执行日志
   登录Supabase控制台，进入对应的Edge函数页面，查看函数的执行日志，定位具体的错误点（比如获取用户失败、删除用户失败等）。

5. 优化Flutter端的错误捕获
   可以在catch块中尝试获取响应的原始内容，进一步排查问题：

   catch (e) {
     debugPrint(e.toString());
     // 尝试获取函数返回的原始响应
     try {
       final response = await supabase.functions.invoke(
         "delete-user",
         headers: {
           'Authorization': 'Bearer ${supabase.auth.currentSession?.accessToken}'
         },
       );
       debugPrint('Raw response: ${response.data}');
     } catch (innerE) {
       debugPrint('Failed to get raw response: ${innerE.toString()}');
     }
   }
   

内容的提问来源于stack exchange，提问作者Sela404