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>

4 files changed, 49 insertions, 9 deletions

diff --git a/lib/internal/main/check_syntax.js b/lib/internal/main/check_syntax.js
index 7df70b2720..8c73d522ed 100644
--- a/lib/internal/main/check_syntax.js
+++ b/lib/internal/main/check_syntax.js
@@ -11,12 +11,18 @@ const {
   readStdin
 } = require('internal/process/execution');
 
-const CJSModule = require('internal/modules/cjs/loader');
+const { pathToFileURL } = require('url');
+
 const vm = require('vm');
 const {
   stripShebang, stripBOM
 } = require('internal/modules/cjs/helpers');
 
+let CJSModule;
+function CJSModuleInit() {
+  if (!CJSModule)
+    CJSModule = require('internal/modules/cjs/loader');
+}
 
 if (process.argv[1] && process.argv[1] !== '-') {
   // Expand process.argv[1] into a full path.
@@ -25,7 +31,7 @@ if (process.argv[1] && process.argv[1] !== '-') {
 
   // TODO(joyeecheung): not every one of these are necessary
   prepareMainThreadExecution();
-
+  CJSModuleInit();
   // Read the source.
   const filename = CJSModule._resolveFilename(process.argv[1]);
 
@@ -34,20 +40,40 @@ if (process.argv[1] && process.argv[1] !== '-') {
 
   markBootstrapComplete();
 
-  checkScriptSyntax(source, filename);
+  checkSyntax(source, filename);
 } else {
   // TODO(joyeecheung): not every one of these are necessary
   prepareMainThreadExecution();
+  CJSModuleInit();
   markBootstrapComplete();
 
   readStdin((code) => {
-    checkScriptSyntax(code, '[stdin]');
+    checkSyntax(code, '[stdin]');
   });
 }
 
-function checkScriptSyntax(source, filename) {
+function checkSyntax(source, filename) {
   // Remove Shebang.
   source = stripShebang(source);
+
+  const { getOptionValue } = require('internal/options');
+  const experimentalModules = getOptionValue('--experimental-modules');
+  if (experimentalModules) {
+    let isModule = false;
+    if (filename === '[stdin]' || filename === '[eval]') {
+      isModule = getOptionValue('--entry-type') === 'module';
+    } else {
+      const resolve = require('internal/modules/esm/default_resolve');
+      const { format } = resolve(pathToFileURL(filename).toString());
+      isModule = format === 'module';
+    }
+    if (isModule) {
+      const { ModuleWrap } = internalBinding('module_wrap');
+      new ModuleWrap(source, filename);
+      return;
+    }
+  }
+
   // Remove BOM.
   source = stripBOM(source);
   // Wrap it.
diff --git a/lib/internal/main/eval_stdin.js b/lib/internal/main/eval_stdin.js
index 2a2ef6d38a..4face9e61e 100644
--- a/lib/internal/main/eval_stdin.js
+++ b/lib/internal/main/eval_stdin.js
@@ -7,6 +7,7 @@ const {
 } = require('internal/bootstrap/pre_execution');
 
 const {
+  evalModule,
   evalScript,
   readStdin
 } = require('internal/process/execution');
@@ -16,5 +17,8 @@ markBootstrapComplete();
 
 readStdin((code) => {
   process._eval = code;
-  evalScript('[stdin]', process._eval, process._breakFirstLine);
+  if (require('internal/options').getOptionValue('--entry-type') === 'module')
+    evalModule(process._eval);
+  else
+    evalScript('[stdin]', process._eval, process._breakFirstLine);
 });
diff --git a/lib/internal/main/eval_string.js b/lib/internal/main/eval_string.js
index 953fab386d..b032281925 100644
--- a/lib/internal/main/eval_string.js
+++ b/lib/internal/main/eval_string.js
@@ -6,11 +6,15 @@
 const {
   prepareMainThreadExecution
 } = require('internal/bootstrap/pre_execution');
-const { evalScript } = require('internal/process/execution');
+const { evalModule, evalScript } = require('internal/process/execution');
 const { addBuiltinLibsToObject } = require('internal/modules/cjs/helpers');
 
-const source = require('internal/options').getOptionValue('--eval');
+const { getOptionValue } = require('internal/options');
+const source = getOptionValue('--eval');
 prepareMainThreadExecution();
 addBuiltinLibsToObject(global);
 markBootstrapComplete();
-evalScript('[eval]', source, process._breakFirstLine);
+if (getOptionValue('--entry-type') === 'module')
+  evalModule(source);
+else
+  evalScript('[eval]', source, process._breakFirstLine);
diff --git a/lib/internal/main/repl.js b/lib/internal/main/repl.js
index e6b9885351..c2bf54f8bb 100644
--- a/lib/internal/main/repl.js
+++ b/lib/internal/main/repl.js
@@ -13,6 +13,12 @@ const {
 
 prepareMainThreadExecution();
 
+// --entry-type flag not supported in REPL
+if (require('internal/options').getOptionValue('--entry-type')) {
+  console.error('Cannot specify --entry-type for REPL');
+  process.exit(1);
+}
+
 const cliRepl = require('internal/repl');
 cliRepl.createInternalRepl(process.env, (err, repl) => {
   if (err) {