feat: add support for jsconfig.json (#199)

* feat: add support for jsconfig.json

* Update src/tsconfig-loader.ts

Co-authored-by: Michaël De Boey <info@michaeldeboey.be>

* Update src/__tests__/tsconfig-loader.test.ts

Co-authored-by: Alec Larson <1925840+aleclarson@users.noreply.github.com>

* optimize readdir mock

* add changelog

* update readme

Co-authored-by: Michaël De Boey <info@michaeldeboey.be>
Co-authored-by: Alec Larson <1925840+aleclarson@users.noreply.github.com>

CHANGELOG.md

@@ -7,6 +7,8 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [Unreleased]
 
+- Add support for `jsconfig.json`. See PR [#199](https://github.com/dividab/tsconfig-paths/pull/199). Thanks to [@F3n67u](https://github.com/F3n67u) for this PR!
+
 ## [3.14.1] - 2022-03-22
 
 ### Fixed

README.md

@@ -6,11 +6,11 @@
 [![MIT license][license-image]][license-url]
 [![code style: prettier][prettier-image]][prettier-url]
 
-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.
+Use this to load modules whose location is specified in the `paths` section of `tsconfig.json` or `jsconfig.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 you require this package's `tsconfig-paths/register` module it will read the `paths` from `tsconfig.json` or `jsconfig.json` and convert node's module loading calls into to physical file paths that node can load.
 
 ## How to install
 
@@ -156,7 +156,7 @@ export interface ExplicitParams {
 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.
+This function will patch the node's module loading so it will look for modules in paths specified by `tsconfig.json` or `jsconfig.json`.
 A function is returned for you to reinstate Node's original module loading.
 
 ### loadConfig
@@ -180,7 +180,7 @@ export interface ConfigLoaderFailResult {
 }
 ```
 
-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.
+This function loads the `tsconfig.json` or `jsconfig.json`. It will start searching from the specified `cwd` directory. Passing the `tsconfig.json` or `jsconfig.json` file directly instead of a directory also works.
 
 ### createMatchPath
 

src/__tests__/tsconfig-loader.test.ts

@@ -107,27 +107,67 @@ describe("tsconfig-loader", () => {
 describe("walkForTsConfig", () => {
   it("should find tsconfig in starting directory", () => {
     const pathToTsconfig = join("/root", "dir1", "tsconfig.json");
+    const mockFiles: Record<string, string[]> = {
+      "/root/dir1": ["tsconfig.json"],
+    };
+    const res = walkForTsConfig(
+      join("/root", "dir1"),
+      (path) => mockFiles[path] || []
+    );
+    expect(res).toBe(pathToTsconfig);
+  });
+
+  it("should find jsconfig in starting directory", () => {
+    const pathToJsconfig = join("/root", "dir1", "jsconfig.json");
+    const mockFiles: Record<string, string[]> = {
+      "/root/dir1": ["jsconfig.json"],
+    };
+    const res = walkForTsConfig(
+      join("/root", "dir1"),
+      (path) => mockFiles[path] || []
+    );
+    expect(res).toBe(pathToJsconfig);
+  });
+
+  // see https://github.com/Microsoft/TypeScript/issues/15869#issuecomment-301845650
+  it("tsconfig.json take precedence over jsconfig.json when both exist", () => {
+    const pathToTsconfig = join("/root/dir1", "tsconfig.json");
+    const mockFiles: Record<string, string[]> = {
+      "/root/dir1": ["jsconfig.json", "tsconfig.json"],
+    };
     const res = walkForTsConfig(
       join("/root", "dir1"),
-      (path) => path === pathToTsconfig
+      (path) => mockFiles[path] || []
     );
-    // assert.equal(res, pathToTsconfig);
     expect(res).toBe(pathToTsconfig);
   });
 
   it("should find tsconfig in parent directory", () => {
     const pathToTsconfig = join("/root", "tsconfig.json");
+    const mockFiles: Record<string, string[]> = {
+      "/root": ["tsconfig.json"],
+    };
+    const res = walkForTsConfig(
+      join("/root", "dir1"),
+      (path) => mockFiles[path] || []
+    );
+    expect(res).toBe(pathToTsconfig);
+  });
+
+  it("should find jsconfig in parent directory", () => {
+    const pathToTsconfig = join("/root", "jsconfig.json");
+    const mockFiles: Record<string, string[]> = {
+      "/root": ["jsconfig.json"],
+    };
     const res = walkForTsConfig(
       join("/root", "dir1"),
-      (path) => path === pathToTsconfig
+      (path) => mockFiles[path] || []
     );
-    // assert.equal(res, pathToTsconfig);
     expect(res).toBe(pathToTsconfig);
   });
 
   it("should return undefined when reaching the top", () => {
-    const res = walkForTsConfig(join("/root", "dir1", "kalle"), () => false);
-    // assert.equal(res, undefined);
+    const res = walkForTsConfig(join("/root", "dir1", "kalle"), () => []);
     expect(res).toBeUndefined();
   });
 });

src/tsconfig-loader.ts

@@ -90,25 +90,26 @@ function resolveConfigPath(cwd: string, filename?: string): string | undefined {
   const configAbsolutePath = walkForTsConfig(cwd);
   return configAbsolutePath ? path.resolve(configAbsolutePath) : undefined;
 }
-
 export function walkForTsConfig(
   directory: string,
-  // eslint-disable-next-line no-shadow
-  existsSync: (path: string) => boolean = fs.existsSync
+  readdirSync: (path: string) => string[] = fs.readdirSync
 ): string | undefined {
-  const configPath = path.join(directory, "./tsconfig.json");
-  if (existsSync(configPath)) {
-    return configPath;
+  const files = readdirSync(directory);
+  const filesToCheck = ["tsconfig.json", "jsconfig.json"];
+  for (const fileToCheck of filesToCheck) {
+    if (files.indexOf(fileToCheck) !== -1) {
+      return path.join(directory, fileToCheck);
+    }
   }
 
-  const parentDirectory = path.join(directory, "../");
+  const parentDirectory = path.dirname(directory);
 
   // If we reached the top
   if (directory === parentDirectory) {
     return undefined;
   }
 
-  return walkForTsConfig(parentDirectory, existsSync);
+  return walkForTsConfig(parentDirectory, readdirSync);
 }
 
 export function loadTsconfig(