Typesafety improvements

.changeset/typesafety.md

@@ -0,0 +1,138 @@
+---
+"@react-router/dev": minor
+"react-router": minor
+---
+
+### Typesafety improvements
+
+React Router now generates types for each of your route modules.
+You can access those types by importing them from `./+types/<route filename without extension>`.
+For example:
+
+```ts
+// app/routes/product.tsx
+import type * as Route from "./+types/product";
+
+export function loader({ params }: Route.LoaderArgs) {}
+
+export default function Component({ loaderData }: Route.ComponentProps) {}
+```
+
+This initial implementation targets type inference for:
+
+- `Params` : Path parameters from your routing config in `routes.ts` including file-based routing
+- `LoaderData` : Loader data from `loader` and/or `clientLoader` within your route module
+- `ActionData` : Action data from `action` and/or `clientAction` within your route module
+
+These types are then used to create types for route export args and props:
+
+- `LoaderArgs`
+- `ClientLoaderArgs`
+- `ActionArgs`
+- `ClientActionArgs`
+- `HydrateFallbackProps`
+- `ComponentProps` (for the `default` export)
+- `ErrorBoundaryProps`
+
+In the future, we plan to add types for the rest of the route module exports: `meta`, `links`, `headers`, `shouldRevalidate`, etc.
+We also plan to generate types for typesafe `Link`s:
+
+```tsx
+<Link to="/products/:id" params={{ id: 1 }} />
+//        ^^^^^^^^^^^^^          ^^^^^^^^^
+// typesafe `to` and `params` based on the available routes in your app
+```
+
+#### Setup
+
+React Router will generate types into a `.react-router/` directory at the root of your app.
+This directory is fully managed by React Router and is derived based on your route config (`routes.ts`).
+
+👉 ** Add `.react-router/` to `.gitignore` **
+
+```txt
+.react-router
+```
+
+You should also ensure that generated types for routes are always present before running typechecking,
+especially for running typechecking in CI.
+
+👉 ** Add `react-router typegen` to your `typecheck` command in `package.json` **
+
+```json
+{
+  "scripts": {
+    "typecheck": "react-router typegen && tsc"
+  }
+}
+```
+
+To get TypeScript to use those generated types, you'll need to add them to `include` in `tsconfig.json`.
+And to be able to import them as if they files next to your route modules, you'll also need to configure `rootDirs`.
+
+👉 ** Configure `tsconfig.json` for generated types **
+
+```json
+{
+  "include": [".react-router/types/**/*"],
+  "compilerOptions": {
+    "rootDirs": [".", "./.react-router/types"]
+  }
+}
+```
+
+#### `typegen` command
+
+You can manually generate types with the new `typegen` command:
+
+```sh
+react-router typegen
+```
+
+However, manual type generation is tedious and types can get out of sync quickly if you ever forget to run `typegen`.
+Instead, we recommend that you setup our new TypeScript plugin which will automatically generate fresh types whenever routes change.
+That way, you'll always have up-to-date types.
+
+#### TypeScript plugin
+
+To get automatic type generation, you can use our new TypeScript plugin.
+
+👉 ** Add the TypeScript plugin to `tsconfig.json` **
+
+```json
+{
+  "compilerOptions": {
+    "plugins": [{ "name": "@react-router/dev" }]
+  }
+}
+```
+
+We plan to add some other goodies to our TypeScript plugin soon, including:
+
+- Automatic `jsdoc` for route exports that include links to official docs
+- Autocomplete for route exports
+- Warnings for non-HMR compliant exports
+
+##### VSCode
+
+TypeScript looks for plugins registered in `tsconfig.json` in the local `node_modules/`,
+but VSCode ships with its own copy of TypeScript that is installed outside of your project.
+For TypeScript plugins to work, you'll need to tell VSCode to use the local workspace version of TypeScript.
+
+👉 ** Ensure that VSCode is using the workspace version of TypeScript **
+
+This should already be set up for you by a `.vscode/settings.json`:
+
+```json
+{
+  "typescript.tsdk": "node_modules/typescript/lib"
+}
+```
+
+Alternatively, you can open up any TypeScript file and use <kbd>CMD</kbd>+<kbd>SHIFT</kbd>+<kbd>P</kbd> to find `Select TypeScript Version` and then select `Use Workspace Version`. You may need to quit VSCode and reopen it for this setting to take effect.
+
+##### Troubleshooting
+
+In VSCode, open up any TypeScript file in your project and then use <kbd>CMD</kbd>+<kbd>SHIFT</kbd>+<kbd>P</kbd> to select `Open TS Server log`.
+There should be a log for `[react-router] setup` that indicates that the plugin was resolved correctly.
+Then look for any errors in the log.

.vscode/settings.json

@@ -0,0 +1,3 @@
+{
+  "typescript.tsdk": "node_modules/typescript/lib"
+}

decisions/0003-infer-types-for-useloaderdata-and-useactiondata-from-loader-and-action-via-generics.md

@@ -2,7 +2,7 @@
 
 Date: 2022-07-11
 
-Status: accepted
+Status: Superseded by [#0012](./0012-type-inference.md)
 
 ## Context