Question

I am working on a Next.js project using Supabase for the backend. I have defined some helper types to handle the responses from Supabase queries, but I'm running into a TypeScript issue that I can't seem to resolve.

我正在做一个使用Supabase作为后端的Next.js项目。我已经定义了一些帮助器类型来处理来自Supabase查询的响应，但我遇到了一个似乎无法解决的打字问题。

Helper Types:

Here are my helper types and a brief description of each:

以下是我的帮助器类型以及每种帮助器的简要说明：

• DbResult<T>: This type is intended to unwrap the type from a promise. If T is a promise, it infers the type U that the promise resolves to.

  DbResult ：此类型用于从Promise中展开类型。如果T是承诺，则它推断承诺解析为的类型U。

  
  



• DbResultOk<T>: This type is meant to handle successful query results. It infers the data field from the promise and excludes null values.

  DbResultOk ：该类型用于处理成功的查询结果。它从Promise推断数据字段并排除空值。

  
  



• DbResultErr: This type is simply an alias for PostgrestError, intended to handle errors from the Supabase query.

  DbResultErr：该类型只是PostgrestError的别名，用于处理来自Supabase查询的错误。

  
  

export type DbResult<T> = T extends PromiseLike<infer U> ? U : never;
export type DbResultOk<T> = T extends PromiseLike<{ data: infer U }> ? Exclude<U, null> : never;
export type DbResultErr = PostgrestError;

Code:

I am using these types in a function that performs a Supabase query:

我在执行Supabase查询的函数中使用这些类型：

export async function addFrequentIngresoAccion(payload: {
  // ... payload definition
}): Promise<DbResult<any>> {
  const supabase = createServerActionClient<Database>({ cookies });
  const query = supabase.from("FuenteIngreso").insert([/*...*/]).select();
  const result: DbResult<typeof query> = await query;

  if (result.error) {
    const resultErr: DbResultErr = result.error;
    return { error: resultErr };
  }

  const resultOk: DbResultOk<Tables<"FuenteIngreso">[]> = result.data as Tables<"FuenteIngreso">[];
  return { data: resultOk };
}

The line const resultOk: DbResultOk<Tables<"FuenteIngreso">[]> = result.data as Tables<"FuenteIngreso">[]; is throwing the following error:

行Const ResultOk：DbResultOk []>=Result.data as Tables<“FuenteIngreso”>[]；引发以下错误：

Type '{ CantidadIngresoRecurrente: number | null; created_at: string; es_recurrente: boolean | null; fechadepositorecurrente: string | null; fuente_name: string; id: number; LastIngresoAdded: string | null; user_id: string; }[]' is not assignable to type 'never'.ts(2322)

I don't understand why the type is falling back to never. Can anyone help me understand what's going wrong here? Also, if my understanding of the helper types is incorrect, please feel free to correct me.

我不明白为什么这种类型会倒退到永远不会。有没有人能帮我弄明白这里出了什么问题？另外，如果我对帮手类型的理解不正确，请随时纠正我。

I literally just encountered this exact issue today... what are the odds. For me it was the return value of a Supabase Postgres Function and not a table but I think the change should be exactly what you need or close enough.

我今天确实遇到了这个问题……这几率有多大。对我来说，它是Supabase Postgres函数的返回值，而不是表，但我认为更改应该恰好是您需要的，或者足够接近。

Change this line:

更改此行：

const resultOk: DbResultOk<Tables<"FuenteIngreso">[]> = result.data as Tables<"FuenteIngreso">[];

to this:

对此：

const resultOk: DbResultOk<typeof query> = result.data

Why this change?

为什么会有这样的变化？

DbResultOk is defined as this:

DbResultOk的定义如下：

export type DbResultOk<T> = T extends PromiseLike<{ data: infer U }> ? Exclude<U, null> : never

It is similar to the DbResult definition:

它类似于DbResult定义：

export type DbResult<T> = T extends PromiseLike<infer U> ? U : never

Except that generic type T is referencing the data part of the query Result object. Long story short though, it must also be typeof query like DbResult because T must extend PromiseLike<>.

只是泛型类型T引用的是查询结果对象的数据部分。长话短说，它还必须是像DbResult这样的查询类型，因为T必须扩展PromiseLike<>。

This is part of a larger concept in TS called Conditional Types, and TS documentation about this can be found here:
https://www.typescriptlang.org/docs/handbook/2/conditional-types.html

这是TS中称为条件类型的更大概念的一部分，有关这一概念的TS文档可以在以下位置找到：https://www.typescriptlang.org/docs/handbook/2/conditional-types.html