tslint-react-hooks
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TSLint rule that enforces the Rules of Hooks
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# TSLint Rules of Hooks
[](https://www.npmjs.com/package/tslint-react-hooks)
[](https://www.npmjs.com/package/tslint-react-hooks)
[](https://github.com/Gelio/tslint-react-hooks/blob/master/LICENSE.md)
[](https://github.com/Gelio/tslint-react-hooks)
[](https://dev.azure.com/vorenygelio/vorenygelio/_build/latest?definitionId=3&branchName=master)
A TSLint rule that enforces the [Rules of Hooks](https://reactjs.org/docs/hooks-rules.html) for
React hooks.
The rule is based on an [ESLint plugin for react hooks](https://github.com/facebook/react/blob/master/packages/eslint-plugin-react-hooks/README.md).
## Features
- detects using React hooks inside potentially-conditional branches:
- if statements
- short-circuit conditional expressions (`&&`, `||`)
- ternary expressions
- loops (`while`, `for`, `do ... while`)
- functions that themselves are not custom hooks or components
- detects using React hooks in spite of an early return
- support for detecting hooks from namespaces other than `React` (e.g. `MyHooks.useHook`) (**optional**)
## Installation
First, install [the rule](https://www.npmjs.com/package/tslint-react-hooks):
```sh
npm install tslint-react-hooks --save-dev
```
Then, enable the rule by modifying `tslint.json`:
```js
{
"extends": [
// your other plugins...
"tslint-react-hooks"
],
"rules": {
// your other rules...
"react-hooks-nesting": "error"
}
}
```
To use report rule violations as warnings intead of errors, set it to `"warning"`.
## Options
While the rule works fine out-of-the-box, it can be customized. To specify options, use the
following syntax when modifying `tslint.json`:
```js
{
"extends": [
// your other plugins...
"tslint-react-hooks"
],
"rules": {
// your other rules...
"react-hooks-nesting": {
"severity": "error", // "error", "warning", "default" or "off"
"options": {
// options go here
}
}
}
}
```
### Available options
- `"detect-hooks-from-non-react-namespace"` - when set to `true`, violations will be also reported
hooks accessed from sources other than the `React` namespace (e.g. `MyHooks.useHook` will be
treated as a hook).
By default, only direct calls (e.g. `useHook`) or calls from `React` namespace (e.g.
`React.useState`) are treated as hooks.
Have an idea for an option? [Create a new issue](https://github.com/Gelio/tslint-react-hooks/issues/new).
## Workarounds
For some arrow functions/function expressions, the rule has no way to determine whether those are a
component, a hook, both of which could contain hook calls, or a regular function that should not
contain hook calls.
```ts
const withHoc = <TProps extends object>(Component: ComponentType<TProps>) => (
props: TProps,
) => {
const [state] = useState();
return <Component {...props} />;
};
```
The workaround in those cases is to use a **named function expression**:
```ts
const withHoc = <TProps extends object>(Component: ComponentType<TProps>) =>
function WrappedComponent(props: TProps) {
const [state] = useState();
return <Component {...props} />;
};
```
Naming the function like a component (in _PascalCase_) unambiguously lets the rule treat the
function as a component.
## False positives and not-covered cases
There are some cases that seem hard to analyze and may result in false positives or false negatives.
In such cases, disable the rule for a specific line using the following comment:
```ts
// tslint:disable:react-hooks-nesting
useEffect(() => {});
```
### Looping over static arrays
The rule may report false positives, for example in:
```ts
function MyComponent() {
const array = [1, 2, 3];
array.forEach(value => {
React.useEffect(() => console.log(value));
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ [A hook cannot be used inside of another function]
});
}
```
The `useEffect` hook will be called unconditionally and the call-order will be the same between
renders.
### Using renamed hooks (that do not start with _use_)
The rule only treats functions that start with _use_ as hooks. Therefore, renaming the hook will
result in avoiding the rule:
```ts
const renamedUseState = React.useState;
function MyComponent() {
const [state, setState] = renamedUseState(0);
}
```
### Unconditional nesting
Unconditional nesting, for example:
```tsx
function MyComponent() {
if (true) {
const variableThatCannotBeLeaked = useContext(SomeContext);
useEffect(() => {
console.log(variableThatCannotBeLeaked);
});
}
return <div>Text</div>;
}
```
is treated as conditional nesting. It seems hard to verify if the condition is in fact a constant,
therefore such a situation will always result in a rule violation.
In situations where such an `if` statement was used to create an additional block scope, use the
block scope directly:
```tsx
function MyComponent() {
{
const variableThatCannotBeLeaked = useContext(SomeContext);
useEffect(() => {
console.log(variableThatCannotBeLeaked);
});
}
return <div>Text</div>;
}
```
## Development
After pulling the repository, make sure to run
```sh
npm install
```
The source code for the rule is located in the `src` directory.
For more information about the developing custom TSLint rules, take a look at
[TSLint's documentation](https://palantir.github.io/tslint/develop/custom-rules/).
### Testing the rule
Run
```sh
npm run test
```
to compile the rule and run automatic TSLint tests.
They are located in the `test` directory.
## Author
The author of this rule is Grzegorz Rozdzialik.