Use this to load modules whose location is specified in the `paths` section of `tsconfig.json`. Both loading at run-time and via API are supported.
Typescript by default mimics the Node.js runtime resolution strategy of modules. But it also allows the use of [path mapping](https://www.typescriptlang.org/docs/handbook/module-resolution.html) which allows arbitrary module paths (that doesn't start with "/" or ".") to be specified and mapped to physical paths in the filesystem. The typescript compiler can resolve these paths from `tsconfig` so it will compile OK. But if you then try to execute the compiled files with node (or ts-node), it will only look in the `node_modules` folders all the way up to the root of the filesystem and thus will not find the modules specified by `paths` in `tsconfig`.
If you require this package's `tsconfig-paths/register` module it will read the `paths` from `tsconfig.json` and convert node's module loading calls into to physical file paths that node can load.
If `process.env.TS_NODE_PROJECT` is set it will be used to resolved tsconfig.json
### With webpack
For webpack please use the [tsconfig-paths-webpack-plugin](https://github.com/dividab/tsconfig-paths-webpack-plugin).
### With mocha and ts-node
As of Mocha >= 4.0.0 the `--compiler` was [deprecated](https://github.com/mochajs/mocha/wiki/compilers-deprecation). Instead `--require` should be used. You also have to specify a glob that includes `.ts` files because mocha looks after files with `.js` extension by default.
As long as the command has something similar to a `--require` option that can load a module before it starts, tsconfig-paths should be able to work with it.
If you want more granular control over tsconfig-paths you can bootstrap it. This can be useful if you for instance have compiled with `tsc` to another directory where `tsconfig.json` doesn't exists.
* Installs a custom module load function that can adhere to paths in tsconfig.
*/
export function register(explicitParams: ExplicitParams): () => void;
```
This function will patch the node's module loading so it will look for modules in paths specified by tsconfig.json.
A function is returned for you to reinstate Node's original module loading.
### loadConfig
```typescript
export function loadConfig(cwd: string = process.cwd()): ConfigLoaderResult;
export type ConfigLoaderResult =
| ConfigLoaderSuccessResult
| ConfigLoaderFailResult;
export interface ConfigLoaderSuccessResult {
resultType: "success";
absoluteBaseUrl: string;
paths: { [key: string]: Array<string> };
}
export interface ConfigLoaderFailResult {
resultType: "failed";
message: string;
}
```
This function loads the tsconfig.json. It will start searching from the specified `cwd` directory. Passing the tsconfig.json file directly instead of a directory also works.
### createMatchPath
```typescript
/**
* Function that can match a path
*/
export interface MatchPath {
(
requestedModule: string,
readJson?: Filesystem.ReadJsonSync,
fileExists?: (name: string) => boolean,
extensions?: ReadonlyArray<string>
): string | undefined;
}
/**
* Creates a function that can resolve paths according to tsconfig paths property.
*@param absoluteBaseUrl Absolute version of baseUrl as specified in tsconfig.
*@param paths The paths as specified in tsconfig.
*@param mainFields A list of package.json field names to try when resolving module files.
*@param addMatchAll Add a match-all "*" rule if none is present
The `createMatchPath` function will create a function that can match paths. It accepts `baseUrl` and `paths` directly as they are specified in tsconfig and will handle resolving paths to absolute form. The created function has the signature specified by the type `MatchPath` above.
