# Other

This section is a collection of common issues related to the implementation of `Module Federation` in general(not specific error code).
The main goal is to provide additional context and solution paths for beginners not familiar with the fundamental ways of how `Module Federation` is working at its core.

## Warning: Invalid hook call. Hooks can only be called inside of the body of a function component. This could happen for one of the following reasons:
#### Error Message
:::danger Browser Error Message
Warning: Invalid hook call. Hooks can only be called inside of the body of a function component. This could happen for one of the following reasons:

You might have mismatching versions of React and the renderer (such as React DOM)

You might be breaking the Rules of Hooks

You might have more than one copy of React in the same app
:::

:::danger Browser Error Message
Uncaught TypeError: Cannot read properties on null (reading `useState`)
:::

#### Solution

This error is a React multi-instance problem, which usually occurs when react does not reuse the same instance.
This problem can be avoided by setting `shared` and setting `singleton: true` singleton mode.

```ts title="modern.config.js"
{
    ...
    new ModuleFederationPlugin({
            ...,
         // Default basic configuration
         // shared: [
         //   'react',
         //   'react-dom',
         //   'my-custom-module'
         // ]

         // Configuration with more specificity
            shared: {
                react: { singleton: true, },
                'react-dom': { singleton: true, },
                'my-custom-module': { singleton: true, },
                ...
            },
        })
      ])
  }
```

## Unable to compile federated types, Error: compile TS failed

#### Error Message
:::danger Browser Error Message
Unable to compile federated types, Error: compile TS failed, the original command is 'npx tsc --project file-path.json'.
:::

:::danger Browser Error Message
Error: ENOENT: no such file or directory, open 'project-path/rspack_hmr/application-name/dist/@mf-types.zip'
:::

#### Solution

1. Execute `npx tsc --project file-path.json` according to the error message to solve all type problems encountered.
2. Check your `ModuleFederationPlugin` config field `exposes`:

```ts title="[modern|rspack|rsbuild|webpack].config.[js,ts]"
new ModuleFederationPlugin({
    ...
    // Make sure both key and value start with "./"
    exposes: { './Foo': './src/<path-to-file>/Foo.tsx' },
    ...
  })
```