fix(babel-plugin-import-path-remapper): remap packages with exports field

.changeset/fix-remapper-exports.md

@@ -0,0 +1,5 @@
+---
+"@rnx-kit/babel-plugin-import-path-remapper": patch
+---
+
+Fix lib/ → src/ remapping for packages with an `exports` field in package.json. Previously, packages declaring `exports` were skipped entirely, causing bundlers to load pre-built files instead of source during development.

packages/babel-plugin-import-path-remapper/src/index.js

@@ -45,25 +45,36 @@ function findMainSourceFile(sourcePath, requester, customRemap) {
     resolveOptions
   );
 
-  const { main, exports } = readPackage(manifestPath);
-  if (exports) {
-    // Skip packages that declare entry points
-    return;
+  const { main, exports: pkgExports } = readPackage(manifestPath);
+
+  // Determine the main entry point from `main` or `exports["."]`
+  let mainEntry = typeof main === "string" ? main : undefined;
+  if (!mainEntry && pkgExports) {
+    const root = pkgExports["."];
+    if (typeof root === "string") {
+      mainEntry = root;
+    } else if (root && typeof root === "object") {
+      // Prefer a TypeScript source entry (.ts/.tsx but not .d.ts)
+      const tsEntry = Object.values(root).find(
+        (v) => typeof v === "string" && /\.tsx?$/.test(v) && !/\.d\.ts$/.test(v)
+      );
+      mainEntry = tsEntry || root.default || root.require || root.import;
+    }
   }
 
   if (customRemap) {
     return customRemap(
       sourcePath,
-      typeof main === "string" ? main : undefined,
+      typeof mainEntry === "string" ? mainEntry : undefined,
       requester
     );
   }
 
-  if (typeof main !== "string") {
+  if (typeof mainEntry !== "string") {
     return;
   }
 
-  const remappedPath = `${sourcePath}/${main.replace(
+  const remappedPath = `${sourcePath}/${mainEntry.replace(
     /^(?:\.\/)?lib\/(.*)\.js/,
     "src/$1.ts"
   )}`;

packages/babel-plugin-import-path-remapper/test/__fixtures__/with-exports-dts/node_modules/@rnx-kit/dts-example/lib/index.js

@@ -0,0 +1,2 @@
+"use strict";
+exports.A = 0;

packages/babel-plugin-import-path-remapper/test/__fixtures__/with-exports-dts/node_modules/@rnx-kit/dts-example/package.json

@@ -0,0 +1,11 @@
+{
+  "name": "@rnx-kit/dts-example",
+  "version": "0.0.0-dev",
+  "exports": {
+    ".": {
+      "types": "./lib/index.d.ts",
+      "default": "./lib/index.js"
+    },
+    "./package.json": "./package.json"
+  }
+}

packages/babel-plugin-import-path-remapper/test/__fixtures__/with-exports-ts/node_modules/@rnx-kit/ts-example/lib/index.js

@@ -0,0 +1,2 @@
+"use strict";
+exports.A = 0;

packages/babel-plugin-import-path-remapper/test/__fixtures__/with-exports-ts/node_modules/@rnx-kit/ts-example/package.json

@@ -0,0 +1,12 @@
+{
+  "name": "@rnx-kit/ts-example",
+  "version": "0.0.0-dev",
+  "exports": {
+    ".": {
+      "types": "./lib/index.d.ts",
+      "source": "./src/index.ts",
+      "default": "./lib/index.js"
+    },
+    "./package.json": "./package.json"
+  }
+}

packages/babel-plugin-import-path-remapper/test/__fixtures__/with-exports-ts/node_modules/@rnx-kit/ts-example/src/index.ts

@@ -0,0 +1 @@
+export const A = 0;

packages/babel-plugin-import-path-remapper/test/__fixtures__/with-exports/node_modules/@rnx-kit/example/lib/index.js

@@ -0,0 +1 @@
+module.exports = {};

packages/babel-plugin-import-path-remapper/test/__fixtures__/with-exports/node_modules/@rnx-kit/example/package.json

@@ -0,0 +1,12 @@
+{
+  "name": "@rnx-kit/example",
+  "version": "0.0.0-dev",
+  "main": "lib/index.js",
+  "exports": {
+    ".": {
+      "types": "./lib/index.d.ts",
+      "default": "./lib/index.js"
+    },
+    "./package.json": "./package.json"
+  }
+}

packages/babel-plugin-import-path-remapper/test/__fixtures__/with-exports/node_modules/@rnx-kit/example/src/index.ts

@@ -0,0 +1 @@
+export {};

packages/babel-plugin-import-path-remapper/test/babel-plugin-import-path-remapper.test.ts

@@ -161,4 +161,48 @@ describe("@rnx-kit/babel-plugin-import-path-remapper", () => {
       `import(/* webpackChunkName: "example" */"@rnx-kit/example/__mocks__/lib/index");`
     );
   });
+
+  it("remaps barrel import for package with exports field", () => {
+    process.chdir("test/__fixtures__/with-exports");
+    equal(
+      transform(`import { A } from "@rnx-kit/example";`),
+      `import { A } from "@rnx-kit/example/src/index.ts";`
+    );
+  });
+
+  it("remaps barrel require for package with exports field", () => {
+    process.chdir("test/__fixtures__/with-exports");
+    equal(
+      transform(`require("@rnx-kit/example");`),
+      `require("@rnx-kit/example/src/index.ts");`
+    );
+  });
+
+  it("uses custom remap for package with exports field", () => {
+    process.chdir("test/__fixtures__/with-exports");
+    equal(
+      transform(`import { A } from "@rnx-kit/example";`, {
+        test: isRNXKit,
+        remap: (moduleName: string, path: string) =>
+          `${moduleName}/__mocks__/${path}`,
+      }),
+      `import { A } from "@rnx-kit/example/__mocks__/lib/index.js";`
+    );
+  });
+
+  it("prefers TypeScript source entry in exports over default", () => {
+    process.chdir("test/__fixtures__/with-exports-ts");
+    equal(
+      transform(`import { A } from "@rnx-kit/ts-example";`),
+      `import { A } from "@rnx-kit/ts-example/./src/index.ts";`
+    );
+  });
+
+  it("does not pick .d.ts entries as the main source", () => {
+    process.chdir("test/__fixtures__/with-exports-dts");
+    equal(
+      transform(`import { A } from "@rnx-kit/dts-example";`),
+      `import { A } from "@rnx-kit/dts-example/src/index.ts";`
+    );
+  });
 });