fix(compartment-mapper): Fix "module" property in package.json

packages/compartment-mapper/NEWS.md

@@ -1,5 +1,12 @@
 User-visible changes to the compartment mapper:
 
+# Next release
+
+- Fixes treatment of packages with a `"module"` property in their
+  `package.json`: When the compartment mapper encounters such a package, every
+  module in that package with `.js` extension including the referenced module
+  will be treated an ESM, as if it had the `.mjs` extension.
+
 # v0.7.0 (2022-03-01)
 
 - *BREAKING:* Archive integrity checks now occur when the archive is loaded

packages/compartment-mapper/src/infer-exports.js

@@ -81,20 +81,18 @@ export const inferExportsEntries = function* inferExportsEntries(
 ) {
   // From lowest to highest precedence, such that later entries override former
   // entries.
-  if (main !== undefined) {
-    yield [name, relativize(main)];
-  }
   if (module !== undefined && tags.has('import')) {
     // In this one case, the key "module" has carried a hint that the
-    // referenced module is an ECMASCript module, and that hint is necessary to
-    // override whatever type might be inferred from the module specifier
-    // extension.
+    // referenced module is an ECMASCript module, and that hint may be
+    // necessary to override whatever type might be inferred from the module
+    // specifier extension.
     const spec = relativize(module);
     types[spec] = 'mjs';
-    yield [name, spec];
-  }
-  if (browser !== undefined && tags.has('browser')) {
+    yield [name, relativize(module)];
+  } else if (browser !== undefined && tags.has('browser')) {
     yield* interpretBrowserExports(name, browser);
+  } else if (main !== undefined) {
+    yield [name, relativize(main)];
   }
   if (exports !== undefined) {
     yield* interpretExports(name, exports, tags);

packages/compartment-mapper/src/node-modules.js

@@ -165,7 +165,7 @@ const moduleParsers = { js: 'mjs', ...uncontroversialParsers };
  * @returns {Record<string, string>}
  */
 const inferParsers = (descriptor, location) => {
-  const { type, parsers } = descriptor;
+  const { type, module, parsers } = descriptor;
   if (parsers !== undefined) {
     if (typeof parsers !== 'object') {
       throw new Error(
@@ -186,7 +186,7 @@ const inferParsers = (descriptor, location) => {
     }
     return { ...uncontroversialParsers, ...parsers };
   }
-  if (type === 'module') {
+  if (type === 'module' || module !== undefined) {
     return moduleParsers;
   }
   if (type === 'commonjs') {

packages/compartment-mapper/test/test-main.js

@@ -20,7 +20,7 @@ const assertFixture = (t, { namespace, globals, globalLexicals }) => {
     receivedGlobalLexical,
     typecommon,
     typemodule,
-    typehybrid,
+    typemoduleImplied,
     typeparsers,
   } = namespace;
 
@@ -52,7 +52,11 @@ const assertFixture = (t, { namespace, globals, globalLexicals }) => {
     [42, 42, 42, 42],
     'parsers-specifying package carries exports',
   );
-  t.is(typehybrid, 42, 'type=module and module= package carries exports');
+  t.deepEqual(
+    typemoduleImplied,
+    [42, 42, 42, 42],
+    'module= package carries exports',
+  );
 };
 
 const fixtureAssertionCount = 11;