Fix invalid string extension replacement

src/match-path.ts

@@ -16,7 +16,7 @@ export type MatchPath = (
  * @param paths The paths specified in tsconfig.
  */
 export function createMatchPath(
-  absoluteBaseUrl:string,
+  absoluteBaseUrl: string,
   paths: { [key: string]: Array<string> }): MatchPath {
 
   // Resolve all paths to absolute form once here, this saves time on each request later
@@ -94,7 +94,9 @@ function tryResolve(physicalPath: string,
 
   if (packageJson && packageJson.main && fileExists(path.join(physicalPath, packageJson.main))) {
     const file = path.join(physicalPath, packageJson.main);
-    return file.replace(path.extname(file), "");
+    const fileExtension = path.extname(file).replace(/^\./, "");
+    const fileExtensionRegex = new RegExp(`\.${fileExtension}$`);
+    return fileExtension ? file.replace(fileExtensionRegex, "") : file;
   }
 
   const indexPath = path.join(physicalPath, "/index");

tests/match-path-tests.ts

@@ -89,6 +89,30 @@ describe('find-path', function () {
     assert.equal(result, "/root/location/mylib/kalle");
   });
 
+  it('should resolve from main field in package.json and correctly remove file extension', () => {
+
+    const matchPath = createMatchPath("/root/", { "lib/*": ["location/*"] });
+    const result = matchPath(
+      "/root/subfolder/file.js",
+      "lib/mylib.js",
+      (_: string) => ({ main: "./kalle.js" }),
+      (name: string) => name === "/root/location/mylib.js/kalle.js",
+      [".ts", ".js"]
+    );
+
+    // Make sure we escape the "."
+    const result2 = matchPath(
+      "/root/subfolder/file.js",
+      "lib/mylibjs",
+      (_: string) => ({ main: "./kallejs" }),
+      (name: string) => name === "/root/location/mylibjs/kallejs",
+      [".ts", ".js"]
+    );
+    console.log(result2);
+    assert.equal(result, "/root/location/mylib.js/kalle");
+    assert.equal(result2, "/root/location/mylibjs/kallejs");
+  });
+
   it('should not locate path that does not match', () => {
 
     const matchPath = createMatchPath("/root/", { "lib/*": ["location/*"] });