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# tsconfig-paths
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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.
## How to install
```
yarn add --dev tsconfig-paths
```
or
```
npm install --save-dev tsconfig-paths
```
## How to use
### With node
`node -r tsconfig-paths/register main.js`
If `process.env.TS_NODE_BASEURL` is set it will override the value of `baseUrl` in tsconfig.json:
`TS_NODE_BASEURL=./dist node -r tsconfig-paths/register main.js`
### With ts-node
`ts-node -r tsconfig-paths/register main.ts`
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.
```bash
mocha -r ts-node/register -r tsconfig-paths/register "test/**/*.ts"
```
### With other commands
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.
### With `ts-node` and VSCode
The following is an example configuration for the `.vscode/launch.json`.
```js
{
"version": "0.2.0",
"configurations": [
{
"name": "Debug Functions",
"request": "launch",
"type": "node",
"runtimeArgs": [
"-r",
"${workspaceFolder}/functions/node_modules/ts-node/register",
"-r",
"${workspaceFolder}/functions/node_modules/tsconfig-paths/register"
],
"args": ["${workspaceFolder}/functions/src/index.ts"],
"cwd": "${workspaceFolder}",
"protocol": "inspector",
"env": {
"NODE_ENV": "development",
"TS_NODE_PROJECT": "${workspaceFolder}/functions/tsconfig.json"
},
"outFiles": ["${workspaceFolder}/functions/lib/**/*.js"]
}
]
}
```
## Bootstrapping with explicit params
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.
For example, create a wrapper script called `tsconfig-paths-bootstrap.js` with the contents below:
```javascript
const tsConfig = require("./tsconfig.json");
const tsConfigPaths = require("tsconfig-paths");
const baseUrl = "./"; // Either absolute or relative path. If relative it's resolved to current working directory.
const cleanup = tsConfigPaths.register({
baseUrl,
paths: tsConfig.compilerOptions.paths,
});
// When path registration is no longer needed
cleanup();
```
Then run with:
`node -r ./tsconfig-paths-bootstrap.js main.js`
## Configuration Options
You can set options by passing them before the script path, via programmatic usage or via environment variables.
```bash
ts-node --project customLocation/tsconfig.json -r tsconfig-paths/register "test/**/*.ts"
```
### CLI and Programmatic Options
_Environment variable denoted in parentheses._
- `-P, --project [path]` Path to TypeScript JSON project file (`TS_NODE_PROJECT`)
## Config loading process
1. Use explicit params passed to register
2. Use `process.env.TS_NODE_PROJECT` to resolve tsConfig.json and the specified baseUrl and paths.
3. Resolves tsconfig.json from current working directory and the specified baseUrl and paths.
## Programmatic use
The public API consists of these functions:
- [register](#register)
- [loadConfig](#loadConfig)
- [createMatchPath](#createMatchPath) / [createMatchPathAsync](#createMatchPathAsync)
- [matchFromAbsolutePaths](#matchFromAbsolutePaths) / [matchFromAbsolutePathsAsync](#matchFromAbsolutePathsAsync)
### register
```typescript
export interface ExplicitParams {
baseUrl: string;
paths: { [key: string]: Array<string> };
mainFields?: Array<string>;
addMatchAll?: boolean;
}
/**
* 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
* @returns a function that can resolve paths.
*/
export function createMatchPath(
absoluteBaseUrl: string,
paths: { [key: string]: Array<string> },
mainFields: string[] = ["main"],
addMatchAll: boolean = true
): MatchPath {
```
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.
### matchFromAbsolutePaths
```typescript
/**
* Finds a path from tsconfig that matches a module load request.
* @param absolutePathMappings The paths to try as specified in tsconfig but resolved to absolute form.
* @param requestedModule The required module name.
* @param readJson Function that can read json from a path (useful for testing).
* @param fileExists Function that checks for existence of a file at a path (useful for testing).
* @param extensions File extensions to probe for (useful for testing).
* @param mainFields A list of package.json field names to try when resolving module files.
* @returns the found path, or undefined if no path was found.
*/
export function matchFromAbsolutePaths(
absolutePathMappings: ReadonlyArray<MappingEntry.MappingEntry>,
requestedModule: string,
readJson: Filesystem.ReadJsonSync = Filesystem.readJsonFromDiskSync,
fileExists: Filesystem.FileExistsSync = Filesystem.fileExistsSync,
extensions: Array<string> = Object.keys(require.extensions),
mainFields: string[] = ["main"]
): string | undefined {
```
This function is lower level and requires that the paths as already been resolved to absolute form and sorted in correct order into an array.
### createMatchPathAsync
This is the async version of `createMatchPath`. It has the same signature but with a callback parameter for the result.
### matchFromAbsolutePathsAsync
This is the async version of `matchFromAbsolutePaths`. It has the same signature but with a callback parameter for the result.
## How to publish
```
yarn version --patch
yarn version --minor
yarn version --major
```
[version-image]: https://img.shields.io/npm/v/tsconfig-paths.svg?style=flat
[version-url]: https://www.npmjs.com/package/tsconfig-paths
[travis-image]: https://travis-ci.com/dividab/tsconfig-paths.svg?branch=master&style=flat
[travis-url]: https://travis-ci.com/dividab/tsconfig-paths
[codecov-image]: https://codecov.io/gh/dividab/tsconfig-paths/branch/master/graph/badge.svg
[codecov-url]: https://codecov.io/gh/dividab/tsconfig-paths
[license-image]: https://img.shields.io/github/license/dividab/tsconfig-paths.svg?style=flat
[license-url]: https://opensource.org/licenses/MIT
[prettier-image]: https://img.shields.io/badge/code_style-prettier-ff69b4.svg
[prettier-url]: https://github.com/prettier/prettier
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