解构泛型类型

Question

我有一个函数，其中某些输入属性取决于其中一个道具的值。所以我定义了一个类型如下，它按预期工作：

enum OrganizationPermission {
    UPDATE = 'organization:update',
    INVITE = 'organization:invite',
}

enum WorkspacePermission {
    UPDATE = 'workspace:update',
    INVITE = 'workspace:invite',
}

enum OrganizationRole {
    MANAGER = 'manager'
}

enum WorkspaceRole {
    MANAGER = 'manager'
}

type RolePermission = {
    [OrganizationPermission.UPDATE]: {
        organizationRole: OrganizationRole,
    },
    [OrganizationPermission.INVITE]: {
        organizationRole: OrganizationRole,
    },
    [WorkspacePermission.UPDATE]: {
        workspaceRole: WorkspaceRole,
    },
}

type Permissions = WorkspacePermission | OrganizationPermission;

type CheckPermissionsArgs<P extends Permissions> = {
    perform: P,
    sustain?: boolean,
} & (P extends keyof RolePermission ? RolePermission[P] : Record<string, never>);

function checkPermissions<P extends Permissions>(props: CheckPermissionsArgs<P>): void {
    // omitted for brevity
}

当我必须扩展这个道具时就会出现问题，如下例所示：

type CheckRolePermissionsArgs<P extends Permissions> = CheckPermissionsArgs<P> & {
    role: string[],
}

function checkRolePermissions<P extends Permissions>({role, ...props}: CheckRolePermissionsArgs<P>): void {
    // Typing error
    checkPermissions(props);
}

Typescript 抱怨说：

TS2345：'Pick 类型的参数

, "执行" | “维持” | Exclude), "role">>' 不可分配给类型为 'CheckPermissionsArgs 的参数

[“执行”]>'。键入'Pick

, "执行" | “维持” | Exclude), "role">>' 不可分配给类型 'CheckRolePermissionsArgs

["perform"] 扩展了 OrganizationPermission | WorkspacePermission.UPDATE ？ RolePermission[CheckRolePermissionsArgs<...>["perform"]] : Record<...>'

如何重构这些类型以避免在第二个示例中强制转换 props 参数？

Answer 1

我认为这是因为 逆变，但这只是我的猜测。欢迎批评我。

请参阅this 答案。

考虑下一个例子：

/**
 * VARIANCE
 */
declare var y: Omit<CheckRolePermissionsArgs<WorkspacePermission.UPDATE>, 'role'>

let x: CheckPermissionsArgs<WorkspacePermission.UPDATE> = y // ok
y = x // ok
checkPermissions(x)

因为checkRolePermissions 是高阶函数：

function checkRolePermissions<P extends Permissions_>(props: CheckRolePermissionsArgs<P>): void {
  // Typing error
  const { role, ...rest } = props
  type Keys = keyof typeof rest // "perform" | "sustain" | Exclude<keyof (P extends keyof RolePermission ? RolePermission[P] : Record<string, never>), "role">
  checkPermissions(rest);
}

TS 无法识别rest 类型，因为它在这个地方有点动态类型。它只在运行时知道。

我认为这里最好的解决方案是拆分CheckPermissionsArgs 类型。

enum OrganizationPermission {
  UPDATE = 'organization:update',
  INVITE = 'organization:invite',

}

enum WorkspacePermission {
  UPDATE = 'workspace:update',
  INVITE = 'workspace:invite',
}


enum OrganizationRole {
  MANAGER = 'manager'
}

enum WorkspaceRole {
  MANAGER = 'manager'
}

type RolePermission = {
  [OrganizationPermission.UPDATE]: {
    organizationRole: OrganizationRole,
  },
  [OrganizationPermission.INVITE]: {
    organizationRole: OrganizationRole,
  },
  [WorkspacePermission.UPDATE]: {
    workspaceRole: WorkspaceRole,
  }
}

type Permissions_ = WorkspacePermission | OrganizationPermission;


type CheckPermissionsArgs<P extends Permissions_> = {
  perform: P,
  sustain?: boolean,
};

type Union<P extends Permissions_> = P extends keyof RolePermission ? RolePermission[P] : Record<string, never>

function checkPermissions<P extends Permissions_>(props: CheckPermissionsArgs<P>, data: Union<P>) {
  // this object has exactly the same type as you have in your question
  const merged = { ...props, ...data } 
}


type CheckRolePermissionsArgs<P extends Permissions_> = CheckPermissionsArgs<P> & {
  role: string[],
}



function checkRolePermissions<P extends Permissions_>({ role, ...rest }: CheckRolePermissionsArgs<P>) {
  // Now, TS is able to infer the type
  return (data: Union<P>) => checkPermissions(rest, data);

}


checkRolePermissions({
  perform: OrganizationPermission.UPDATE,
  sustain: true,
  role: ['sdf']
})({
  organizationRole: OrganizationRole.MANAGER,
}) // ok


checkRolePermissions({
  perform: WorkspacePermission.INVITE,
  sustain: true,
  role: ['sdf']
})({
  organizationRole: OrganizationRole.MANAGER,
}) // expected error

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