feat(oas): add rule to detect duplicated entry in enum (#1485)

docs/reference/openapi-rules.md

@@ -411,6 +411,44 @@ TheBadModel:
         - 8
 ```
 
+### duplicated-entry-in-enum
+
+Each value of an `enum` must be different from one another.
+
+**Recommended:** Yes
+
+**Good Example**
+
+```yaml
+TheGoodModel:
+  type: object
+  properties:
+    number_of_connectors:
+      type: integer
+      description: The number of extension points.
+      enum:
+        - 1
+        - 2
+        - 4
+        - 8
+```
+
+**Bad Example**
+
+```yaml
+TheBadModel:
+  type: object
+  properties:
+    number_of_connectors:
+      type: integer
+      description: The number of extension points.
+      enum:
+        - 1
+        - 2
+        - 3
+        - 2
+```
+
 ## OpenAPI v2.0-only
 
 These rules will only apply to OpenAPI v2.0 documents.

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

@@ -0,0 +1,117 @@
+import { DiagnosticSeverity } from '@stoplight/types';
+import * as ruleset from '../index.json';
+import { RuleType, Spectral } from '../../../spectral';
+
+describe('duplicated-entry-in-enum', () => {
+  const s = new Spectral();
+  s.setRules({
+    'duplicated-entry-in-enum': Object.assign(ruleset.rules['duplicated-entry-in-enum'], {
+      recommended: true,
+      type: RuleType[ruleset.rules['duplicated-entry-in-enum'].type],
+    }),
+  });
+
+  describe('oas2', () => {
+    test('does not report anything for empty object', async () => {
+      const results = await s.run({
+        swagger: '2.0',
+      });
+
+      expect(results).toEqual([]);
+    });
+
+    test('does not report anything when the model valid', async () => {
+      const doc = {
+        swagger: '2.0',
+        definitions: {
+          Test: {
+            type: 'integer',
+            enum: [1, 2, 3],
+          },
+        },
+      };
+
+      const results = await s.run(doc);
+
+      expect(results).toEqual([]);
+    });
+
+    test('identifies enum with duplicated entries', async () => {
+      const doc = {
+        swagger: '2.0',
+        definitions: {
+          Test: {
+            type: 'integer',
+            enum: [1, 2, 3, 4, 5, 2],
+          },
+        },
+      };
+
+      const results = await s.run(doc);
+
+      expect(results).toEqual([
+        {
+          code: 'duplicated-entry-in-enum',
+          message: `A duplicated entry in the enum was found. Error: \`enum\` property should not have duplicate items (items ## 1 and 5 are identical)`,
+          path: ['definitions', 'Test', 'enum'],
+          range: expect.any(Object),
+          severity: DiagnosticSeverity.Warning,
+        },
+      ]);
+    });
+  });
+
+  describe('oas3', () => {
+    test('does not report anything for empty object', async () => {
+      const results = await s.run({
+        openapi: '3.0.0',
+      });
+
+      expect(results).toEqual([]);
+    });
+
+    test('does not report anything when the model is valid', async () => {
+      const doc = {
+        openapi: '3.0.0',
+        components: {
+          schemas: {
+            Test: {
+              type: 'integer',
+              enum: [1, 2, 3],
+            },
+          },
+        },
+      };
+
+      const results = await s.run(doc);
+
+      expect(results).toEqual([]);
+    });
+
+    test('identifies enum with duplicated entries', async () => {
+      const doc = {
+        openapi: '3.0.0',
+        components: {
+          schemas: {
+            Test: {
+              type: 'integer',
+              enum: [1, 2, 3, 4, 5, 2],
+            },
+          },
+        },
+      };
+
+      const results = await s.run(doc);
+
+      expect(results).toEqual([
+        {
+          code: 'duplicated-entry-in-enum',
+          message: `A duplicated entry in the enum was found. Error: \`enum\` property should not have duplicate items (items ## 1 and 5 are identical)`,
+          path: ['components', 'schemas', 'Test', 'enum'],
+          range: expect.any(Object),
+          severity: DiagnosticSeverity.Warning,
+        },
+      ]);
+    });
+  });
+});

src/rulesets/oas/index.json

@@ -95,6 +95,23 @@
         }
       ]
     },
+    "duplicated-entry-in-enum": {
+      "description": "Enum values should not have duplicate entry.",
+      "type": "validation",
+      "severity": 1,
+      "recommended": true,
+      "message": "A duplicated entry in the enum was found. Error: {{error}}",
+      "given": "$..enum",
+      "then": {
+        "function": "schema",
+        "functionOptions": {
+          "schema": {
+            "type": "array",
+            "uniqueItems": true
+          }
+        }
+      }
+    },
     "info-contact": {
       "description": "Info object should contain `contact` object.",
       "recommended": true,

test-harness/scenarios/duplicated-entry-in-enum.oas.scenario

@@ -0,0 +1,33 @@
+====test====
+Identify enum values that does not respect the specified type
+====asset:ruleset====
+extends: [[spectral:oas, off]]
+
+rules:
+  duplicated-entry-in-enum: error
+====document====
+openapi: 3.0.2
+components:
+  schemas:
+    a_model:
+      type: object
+      properties:
+        id:
+          type: integer
+          description: Unique asset identifier
+          enum:
+            - 1
+            - 2
+            - 3
+            - 4
+            - 5
+            - 2
+====command====
+{bin} lint {document} --ruleset {asset:ruleset}
+====stdout====
+OpenAPI 3.x detected
+
+{document}
+ 10:16  error  duplicated-entry-in-enum  A duplicated entry in the enum was found. Error: `enum` property should not have duplicate items (items ## 1 and 5 are identical)  components.schemas.a_model.properties.id.enum
+
+✖ 1 problem (1 error, 0 warnings, 0 infos, 0 hints)

test-harness/scenarios/enabled-rules-amount.oas3.scenario

@@ -24,7 +24,7 @@ components:
 ====command====
 {bin} lint {document} --ruleset ./rulesets/parameter-description.oas3.yaml -v
 ====stdout====
-Found 55 rules (1 enabled)
+Found 56 rules (1 enabled)
 Linting {document}
 OpenAPI 3.x detected