fix: treat null & undefined as no-scope markers

__tests__/plugin.test.js

@@ -136,6 +136,38 @@ describe('commitlintPluginSelectiveScope', () => {
       ).toBe(true)
     })
 
+    // @commitlint/load uses es-toolkit merge, which turns config `[null]` into `[undefined]`.
+    it('should treat undefined in the allowed list as a no-scope marker (commitlint load)', () => {
+      expect(
+        commitlintPluginSelectiveScopeResolverWrapped(
+          { scope: null, type: 'ci' },
+          { ci: [undefined] }
+        )[0]
+      ).toBe(true)
+
+      expect(
+        commitlintPluginSelectiveScopeResolverWrapped(
+          { scope: undefined, type: 'ci' },
+          { ci: [undefined] }
+        )[0]
+      ).toBe(true)
+
+      expect(
+        commitlintPluginSelectiveScopeResolverWrapped(
+          { scope: null, type: 'ci' },
+          { ci: [undefined, 'codebuild'] }
+        )[0]
+      ).toBe(true)
+
+      const [ok, message] = commitlintPluginSelectiveScopeResolverWrapped(
+        { scope: 'github', type: 'ci' },
+        { ci: [undefined, 'codebuild'] }
+      )
+      expect(ok).toBe(false)
+      expect(message).not.toContain('"undefined"')
+      expect(message).toContain('"codebuild"')
+    })
+
     it('should match scope if provided', () => {
       expect(
         commitlintPluginSelectiveScopeResolverWrapped(

index.js

@@ -8,6 +8,19 @@ function normalizeScope(scope) {
   return scope
 }
 
+// @commitlint/load merges config with es-toolkit, which turns array `null`
+// entries into `undefined`. Treat both as "no scope" markers.
+function isNoScopeMarker(value) {
+  return value == null
+}
+
+function formatAllowedScopes(allowedScopes) {
+  return allowedScopes
+    .filter(s => !isNoScopeMarker(s))
+    .map(s => `"${s}"`)
+    .join(', ')
+}
+
 module.exports = {
   rules: {
     'selective-scope': (ctx, applicable, rule) => {
@@ -24,7 +37,7 @@ module.exports = {
       }
 
       if (Array.isArray(allowedScopes)) {
-        // If the type maps to an empty array in the rule config, scope it not allowed
+        // If the type maps to an empty array in the rule config, scope is not allowed
         if (allowedScopes.length === 0) {
           if (scope != null) {
             return [
@@ -36,39 +49,41 @@ module.exports = {
           return [true]
         }
 
-        // Otherwise attempt to match against either null, a string literal, or a RegExp
+        // Otherwise attempt to match against either null/undefined, a string literal, or a RegExp
         if (
           allowedScopes.findIndex(s => {
+            if (isNoScopeMarker(s)) {
+              return scope == null
+            }
+
             if (
               typeof scope === 'string' &&
               Object.prototype.toString.call(s) === '[object RegExp]'
             ) {
               return scope.match(s)
             }
 
-            // Equality comparison works for both strings and null
             return s === scope
           }) !== -1
         ) {
           return [true]
-        } else if (allowedScopes.includes(null)) {
+        } else if (allowedScopes.some(isNoScopeMarker)) {
           return [
             false,
             `commit message with type "${
               ctx.type
-            }" may specify a scope, but if specified, it must be one of the following: ${allowedScopes
-              .filter(s => s !== null)
-              .map(s => `"${s}"`)
-              .join(', ')}`
+            }" may specify a scope, but if specified, it must be one of the following: ${formatAllowedScopes(
+              allowedScopes
+            )}`
           ]
         } else {
           return [
             false,
             `commit message with type "${
               ctx.type
-            }" must specify one of the following scopes: ${allowedScopes
-              .map(s => `"${s}"`)
-              .join(', ')}`
+            }" must specify one of the following scopes: ${formatAllowedScopes(
+              allowedScopes
+            )}`
           ]
         }
       }