esm: phase two of new esm implementation

This PR updates the current `--experimental-modules` implementation
based on the work of the modules team  and reflects Phase 2 of our
new modules plan.

The largest differences from the current implementation include

* `packge.type` which can be either `module` or `commonjs`
  - `type: "commonjs"`:
    - `.js` is parsed as commonjs
    - default for entry point without an extension is commonjs
  - `type: "module"`:
    - `.js` is parsed as esm
    - does not support loading JSON or Native Module by default
    - default for entry point without an extension is esm
* `--entry-type=[mode]`
  - allows you set the type on entry point.
* A new file extension `.cjs`.
  - this is specifically to support importing commonjs in the
    `module` mode.
  - this is only in the esm loader, the commonjs loader remains
    untouched, but the extension will work in the old loader if you use
    the full file path.
* `--es-module-specifier-resolution=[type]`
  - options are `explicit` (default) and `node`
  - by default our loader will not allow for optional extensions in
    the import, the path for a module must include the extension if
    there is one
  - by default our loader will not allow for importing directories that
    have an index file
  - developers can use `--es-module-specifier-resolution=node` to
    enable the commonjs specifier resolution algorithm
  - This is not a “feature” but rather an implementation for
    experimentation. It is expected to change before the flag is
    removed
* `--experimental-json-loader`
  - the only way to import json when `"type": "module"`
  - when enable all `import 'thing.json'` will go through the
    experimental loader independent of mode
  - based on https://github.com/whatwg/html/issues/4315
* You can use `package.main` to set an entry point for a module
  - the file extensions used in main will be resolved based on the
    `type` of the module

Refs: https://github.com/nodejs/modules/blob/master/doc/plan-for-new-modules-implementation.md
Refs: https://github.com/GeoffreyBooth/node-import-file-specifier-resolution-proposal
Refs: https://github.com/nodejs/modules/pull/180
Refs: https://github.com/nodejs/ecmascript-modules/pull/6
Refs: https://github.com/nodejs/ecmascript-modules/pull/12
Refs: https://github.com/nodejs/ecmascript-modules/pull/28
Refs: https://github.com/nodejs/modules/issues/255
Refs: https://github.com/whatwg/html/issues/4315
Refs: https://github.com/w3c/webcomponents/issues/770
Co-authored-by: Myles Borins <MylesBorins@google.com>
Co-authored-by: John-David Dalton <john.david.dalton@gmail.com>
Co-authored-by: Evan Plaice <evanplaice@gmail.com>
Co-authored-by: Geoffrey Booth <webmaster@geoffreybooth.com>
Co-authored-by: Michaël Zasso <targos@protonmail.com>

PR-URL: https://github.com/nodejs/node/pull/26745
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Guy Bedford <guybedford@gmail.com>
Reviewed-By: Ben Coe <bencoe@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Сковорода Никита Андреевич <chalkerx@gmail.com>

18 files changed, 47 insertions, 7 deletions

diff --git a/test/fixtures/es-modules/cjs-file.cjs b/test/fixtures/es-modules/cjs-file.cjs
new file mode 100644
index 0000000000..3d0637686e
--- /dev/null
+++ b/test/fixtures/es-modules/cjs-file.cjs
@@ -0,0 +1 @@
+console.log('.cjs file');
diff --git a/test/fixtures/es-modules/json-cache/another.cjs b/test/fixtures/es-modules/json-cache/another.cjs
new file mode 100644
index 0000000000..8c8e9f1c0f
--- /dev/null
+++ b/test/fixtures/es-modules/json-cache/another.cjs
@@ -0,0 +1,7 @@
+const test = require('./test.json');
+
+module.exports = {
+  ...test
+};
+
+test.one = 'it comes';
diff --git a/test/fixtures/es-modules/json-cache/mod.cjs b/test/fixtures/es-modules/json-cache/mod.cjs
new file mode 100644
index 0000000000..047cfb24a4
--- /dev/null
+++ b/test/fixtures/es-modules/json-cache/mod.cjs
@@ -0,0 +1,7 @@
+const test = require('./test.json');
+
+module.exports = {
+  ...test
+};
+
+test.one = 'zalgo';
diff --git a/test/fixtures/es-modules/json-cache/test.json b/test/fixtures/es-modules/json-cache/test.json
new file mode 100644
index 0000000000..120cbb2840
--- /dev/null
+++ b/test/fixtures/es-modules/json-cache/test.json
@@ -0,0 +1,5 @@
+{
+  "one": 1,
+  "two": 2,
+  "three": 3
+}
diff --git a/test/fixtures/es-modules/json.json b/test/fixtures/es-modules/json.json
deleted file mode 100644
index 8288d42e2b..0000000000
--- a/test/fixtures/es-modules/json.json
+++ /dev/null
@@ -1,3 +0,0 @@
-{
-  "val": 42
-}
diff --git a/test/fixtures/es-modules/loop.mjs b/test/fixtures/es-modules/loop.mjs
index 1b5cab10ed..3d2ddd2eb7 100644
--- a/test/fixtures/es-modules/loop.mjs
+++ b/test/fixtures/es-modules/loop.mjs
@@ -1,4 +1,4 @@
-import { message } from './message';
+import { message } from './message.mjs';
 
 var t = 1;
 var k = 1;
diff --git a/test/fixtures/es-modules/mjs-file.mjs b/test/fixtures/es-modules/mjs-file.mjs
new file mode 100644
index 0000000000..489d4ab570
--- /dev/null
+++ b/test/fixtures/es-modules/mjs-file.mjs
@@ -0,0 +1 @@
+console.log('.mjs file');
diff --git a/test/fixtures/es-modules/noext-esm b/test/fixtures/es-modules/noext-esm
new file mode 100644
index 0000000000..251d6e538a
--- /dev/null
+++ b/test/fixtures/es-modules/noext-esm
@@ -0,0 +1,2 @@
+export default 'module';
+console.log('executed');
diff --git a/test/fixtures/es-modules/package-type-commonjs/index.js b/test/fixtures/es-modules/package-type-commonjs/index.js
new file mode 100644
index 0000000000..009431d851
--- /dev/null
+++ b/test/fixtures/es-modules/package-type-commonjs/index.js
@@ -0,0 +1,3 @@
+const identifier = 'package-type-commonjs';
+console.log(identifier);
+module.exports = identifier;
diff --git a/test/fixtures/es-modules/package-type-commonjs/package.json b/test/fixtures/es-modules/package-type-commonjs/package.json
new file mode 100644
index 0000000000..4aaa4a2388
--- /dev/null
+++ b/test/fixtures/es-modules/package-type-commonjs/package.json
@@ -0,0 +1,4 @@
+{
+  "type": "commonjs",
+  "main": "index.js"
+}
diff --git a/test/fixtures/es-modules/package-type-module/index.js b/test/fixtures/es-modules/package-type-module/index.js
new file mode 100644
index 0000000000..12aba970ef
--- /dev/null
+++ b/test/fixtures/es-modules/package-type-module/index.js
@@ -0,0 +1,3 @@
+const identifier = 'package-type-module';
+console.log(identifier);
+export default identifier;
diff --git a/test/fixtures/es-modules/package-type-module/package.json b/test/fixtures/es-modules/package-type-module/package.json
new file mode 100644
index 0000000000..07aec65d5a
--- /dev/null
+++ b/test/fixtures/es-modules/package-type-module/package.json
@@ -0,0 +1,4 @@
+{
+  "type": "module",
+  "main": "index.js"
+}
diff --git a/test/fixtures/es-modules/package-without-type/index.js b/test/fixtures/es-modules/package-without-type/index.js
new file mode 100644
index 0000000000..a547216cb0
--- /dev/null
+++ b/test/fixtures/es-modules/package-without-type/index.js
@@ -0,0 +1,3 @@
+const identifier = 'package-without-type';
+console.log(identifier);
+module.exports = identifier;
diff --git a/test/fixtures/es-modules/package-without-type/package.json b/test/fixtures/es-modules/package-without-type/package.json
new file mode 100644
index 0000000000..14ab704d8f
--- /dev/null
+++ b/test/fixtures/es-modules/package-without-type/package.json
@@ -0,0 +1,3 @@
+{
+  "main": "index.js"
+}
diff --git a/test/fixtures/es-modules/pjson-main/main.js b/test/fixtures/es-modules/pjson-main/main.js
deleted file mode 100644
index dfdd47b877..0000000000
--- a/test/fixtures/es-modules/pjson-main/main.js
+++ /dev/null
@@ -1 +0,0 @@
-module.exports = 'main';
diff --git a/test/fixtures/es-modules/pjson-main/main.mjs b/test/fixtures/es-modules/pjson-main/main.mjs
new file mode 100644
index 0000000000..9eb0aade18
--- /dev/null
+++ b/test/fixtures/es-modules/pjson-main/main.mjs
@@ -0,0 +1 @@
+export const main = 'main'
diff --git a/test/fixtures/es-modules/pjson-main/package.json b/test/fixtures/es-modules/pjson-main/package.json
index c13b8cf6ac..ea9b784692 100644
--- a/test/fixtures/es-modules/pjson-main/package.json
+++ b/test/fixtures/es-modules/pjson-main/package.json
@@ -1,3 +1,3 @@
 {
-  "main": "main.js"
+  "main": "main.mjs"
 }
diff --git a/test/fixtures/es-modules/test-esm-double-encoding-native%20.js b/test/fixtures/es-modules/test-esm-double-encoding-native%20.mjs
index ea1caa81be..a3bfe972e5 100644
--- a/test/fixtures/es-modules/test-esm-double-encoding-native%20.js
+++ b/test/fixtures/es-modules/test-esm-double-encoding-native%20.mjs
@@ -3,4 +3,4 @@
 // Trivial test to assert we can load files with `%` in their pathname.
 // Imported by `test-esm-double-encoding.mjs`.
 
-module.exports = 42;
+export default 42;