module: resolve self-references

Adds the ability to `import` or `require` a package from within its
own source code. This allows tests and examples to be written using
the package name, making them easier to reuse by consumers of the
package.

Assuming the `name` field in `package.json` is set to `my-pkg`, its
test could use `require('my-pkg')` or `import 'my-pkg'` even if
there's no `node_modules/my-pkg` while testing the package itself.

An important difference between this and relative specifiers like
`require('../')` is that self-references use the public interface
of the package as defined in the `exports` field while relative
specifiers don't.

This behavior is guarded by a new experimental flag
(`--experimental-resolve-self`).

PR-URL: https://github.com/nodejs/node/pull/29327
Reviewed-By: Guy Bedford <guybedford@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>

3 files changed, 15 insertions, 0 deletions

diff --git a/test/fixtures/node_modules/pkgexports/lib/hole.js b/test/fixtures/node_modules/pkgexports/lib/hole.js
new file mode 100644
index 0000000000..124b0932ad
--- /dev/null
+++ b/test/fixtures/node_modules/pkgexports/lib/hole.js
@@ -0,0 +1,10 @@
+'use strict';
+
+module.exports = {
+  async importFromInside(specifier) {
+    return import(specifier);
+  },
+  async requireFromInside(specifier) {
+    return { default: require(specifier) };
+  },
+};
diff --git a/test/fixtures/node_modules/pkgexports/not-exported.js b/test/fixtures/node_modules/pkgexports/not-exported.js
new file mode 100644
index 0000000000..02e146dbe9
--- /dev/null
+++ b/test/fixtures/node_modules/pkgexports/not-exported.js
@@ -0,0 +1,3 @@
+'use strict';
+
+module.exports = 'not-exported';
diff --git a/test/fixtures/node_modules/pkgexports/package.json b/test/fixtures/node_modules/pkgexports/package.json
index 2b190521e5..38e2fc1a5c 100644
--- a/test/fixtures/node_modules/pkgexports/package.json
+++ b/test/fixtures/node_modules/pkgexports/package.json
@@ -1,6 +1,8 @@
 {
+  "name": "@pkgexports/name",
   "exports": {
     ".": "./asdf.js",
+    "./hole": "./lib/hole.js",
     "./space": "./sp%20ce.js",
     "./valid-cjs": "./asdf.js",
     "./sub/": "./",