fix(compartment-mapper): Take only first matching tag of package expo…

…rts (#2275)

Closes: #2276

## Description

If a `package.json` `"exports"` is a list of ordered constraints, Endo’s
Compartment Mapper currently uses all of the accepted entries and not
just the first. This causes subsequent entries to override the first if
they produce matching paths. I believe the intended behavior is to use
the first that matches.

### Security Considerations

This amounts to a difference in behavior between Endo and Node in the
treatment of Package Exports.

### Scaling Considerations

None.

### Documentation Considerations

Fixing this issue will bring Endo into accord with Node.js’s somewhat
light documentation on this feature.

### Testing Considerations

Existing snapshot tests cover the behavior and must be updated to
reflect the correct interpretation.

### Compatibility Considerations

This will improve ecosystem compatibility. No known bundles depend on
the existing behavior, but we cannot rule out the possibility.

There is a possibility that this change will break existing bundles that
depend on the current erroneous behavior, for example preferring
`default` over an `endo` tag. I am considering this a bugfix and not a
breaking change since it is a bug to rely on the current behavior.

### Upgrade Considerations

Even if this behavior might break the bundling process for existing
contracts, it will not invalidate existing bundles. This change should
not break upgrades but may create a speed bump for upgrading tool
dependencies.

packages/compartment-mapper/NEWS.md

@@ -1,5 +1,11 @@
 User-visible changes to the compartment mapper:
 
+# Next release
+
+- Fixes incompatible behavior with Node.js package conditional exports #2276.
+  Previously, the last matching tag would override all prior matches, often
+  causing a bundle to adopt the `default` instead of a more specific condition.
+
 # 0.9.0 (2023-08-07)
 
 - Introduces support for source map generation.

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

@@ -83,6 +83,8 @@ function* interpretExports(name, exports, tags) {
       }
     } else if (tags.has(key)) {
       yield* interpretExports(name, value, tags);
+      // Take only the first matching tag.
+      break;
     }
   }
 }

packages/compartment-mapper/test/snapshots/infer-exports.test.js.md

@@ -24,7 +24,7 @@ Generated by [AVA](https://avajs.dev).
 
     {
       exports: {
-        '.': './underscore-umd.js',
+        '.': './underscore-node.mjs',
         './amd/*': './amd/*',
         './cjs/*': './cjs/*',
         './modules/*': './modules/*',
@@ -42,7 +42,7 @@ Generated by [AVA](https://avajs.dev).
 
     {
       exports: {
-        '.': './dist/vue.runtime.esm-bundler.js',
+        '.': './index.mjs',
         './compiler-sfc': './compiler-sfc/index.mjs',
         './dist/*': './dist/*',
         './macros': './macros.d.ts',
@@ -62,7 +62,7 @@ Generated by [AVA](https://avajs.dev).
 
     {
       exports: {
-        '.': './build/esm/index.js',
+        '.': './build/esm-debug/index.js',
         './dist/socket.io.js': './dist/socket.io.js',
         './dist/socket.io.js.map': './dist/socket.io.js.map',
         './package.json': './package.json',
@@ -78,7 +78,7 @@ Generated by [AVA](https://avajs.dev).
 
     {
       exports: {
-        '.': './lib/index.js',
+        '.': './esm/index.mjs',
         './package.json': './package.json',
       },
       types: {},
@@ -90,7 +90,7 @@ Generated by [AVA](https://avajs.dev).
 
     {
       exports: {
-        '.': './dist/index.exports.require.cjs.js',
+        '.': './dist/index.exports.import.es.mjs',
         './package.json': './package.json',
       },
       types: {
@@ -104,36 +104,36 @@ Generated by [AVA](https://avajs.dev).
 
     {
       exports: {
-        './_sha2': './_sha2.js',
-        './blake2b': './blake2b.js',
+        './_sha2': './esm/_sha2.js',
+        './blake2b': './esm/blake2b.js',
         './blake2b.d.ts': './blake2b.d.ts',
-        './blake2s': './blake2s.js',
+        './blake2s': './esm/blake2s.js',
         './blake2s.d.ts': './blake2s.d.ts',
-        './blake3': './blake3.js',
+        './blake3': './esm/blake3.js',
         './blake3.d.ts': './blake3.d.ts',
-        './crypto': './crypto.js',
-        './eskdf': './eskdf.js',
+        './crypto': './esm/crypto.js',
+        './eskdf': './esm/eskdf.js',
         './eskdf.d.ts': './eskdf.d.ts',
-        './hkdf': './hkdf.js',
+        './hkdf': './esm/hkdf.js',
         './hkdf.d.ts': './hkdf.d.ts',
-        './hmac': './hmac.js',
+        './hmac': './esm/hmac.js',
         './hmac.d.ts': './hmac.d.ts',
-        './index': './index.js',
-        './pbkdf2': './pbkdf2.js',
+        './index': './esm/index.js',
+        './pbkdf2': './esm/pbkdf2.js',
         './pbkdf2.d.ts': './pbkdf2.d.ts',
-        './ripemd160': './ripemd160.js',
+        './ripemd160': './esm/ripemd160.js',
         './ripemd160.d.ts': './ripemd160.d.ts',
-        './scrypt': './scrypt.js',
+        './scrypt': './esm/scrypt.js',
         './scrypt.d.ts': './scrypt.d.ts',
-        './sha256': './sha256.js',
+        './sha256': './esm/sha256.js',
         './sha256.d.ts': './sha256.d.ts',
-        './sha3': './sha3.js',
-        './sha3-addons': './sha3-addons.js',
+        './sha3': './esm/sha3.js',
+        './sha3-addons': './esm/sha3-addons.js',
         './sha3-addons.d.ts': './sha3-addons.d.ts',
         './sha3.d.ts': './sha3.d.ts',
-        './sha512': './sha512.js',
+        './sha512': './esm/sha512.js',
         './sha512.d.ts': './sha512.d.ts',
-        './utils': './utils.js',
+        './utils': './esm/utils.js',
         './utils.d.ts': './utils.d.ts',
       },
       types: {},