fix(rulesets): duplicated-entry-in-enum - support null values

packages/rulesets/src/oas/__tests__/duplicated-entry-in-enum.test.ts

@@ -85,7 +85,7 @@ testRule('duplicated-entry-in-enum', [
   },
 
   {
-    name: 'osa3: enum with duplicated entries',
+    name: 'oas3: enum with duplicated entries',
     document: {
       openapi: '3.0.0',
       components: {
@@ -158,4 +158,62 @@ testRule('duplicated-entry-in-enum', [
     },
     errors: [],
   },
+  {
+    name: 'oas3.1: valid model',
+    document: {
+      openapi: '3.1.0',
+      components: {
+        schemas: {
+          Test: {
+            type: 'integer',
+            enum: [1, 2, 3, null],
+          },
+        },
+      },
+    },
+    errors: [],
+  },
+
+  {
+    name: 'oas3.1: enum with duplicated entries',
+    document: {
+      openapi: '3.1.0',
+      components: {
+        schemas: {
+          Test: {
+            type: 'integer',
+            enum: [1, 2, 3, 4, 5, 2],
+          },
+        },
+      },
+    },
+    errors: [
+      {
+        message: `"enum" property must not have duplicate items (items ## 1 and 5 are identical)`,
+        path: ['components', 'schemas', 'Test', 'enum'],
+        severity: DiagnosticSeverity.Warning,
+      },
+    ],
+  },
+  {
+    name: 'oas3.1: enum with duplicated null entries',
+    document: {
+      openapi: '3.1.0',
+      components: {
+        schemas: {
+          Test: {
+            type: 'integer',
+            enum: [null, 1, 3, 4, 5, 2, null],
+          },
+        },
+      },
+    },
+    errors: [
+      {
+        message: `"enum" property must not have duplicate items (items ## 0 and 6 are identical)`,
+        path: ['components', 'schemas', 'Test', 'enum'],
+        severity: DiagnosticSeverity.Warning,
+      },
+    ],
+  },
 ]);

packages/rulesets/src/oas/index.ts

@@ -159,7 +159,7 @@ const ruleset = {
       severity: 'warn',
       recommended: true,
       message: '{{error}}',
-      given: ["$..[?(@property !== 'properties' && @.enum && @.enum.constructor.name === 'Array')]"],
+      given: ["$..[?(@property !== 'properties' && @ != null && @.enum && @.enum.constructor.name === 'Array')]"],
       then: {
         field: 'enum',
         function: oasSchema,