Bugfix#344 report error when one of schema doesnt have the discriminator property

src/Microsoft.OpenApi/Properties/SRResource.resx

@@ -210,6 +210,12 @@
   <data name="Validation_RuleAddTwice" xml:space="preserve">
     <value>The same rule cannot be in the same rule set twice.</value>
   </data>
+  <data name="Validation_SchemaDoesntContainDiscriminatorProperty" xml:space="preserve">
+    <value>Schema {0} doesn't contain discriminator property {1}.</value>
+  </data>
+  <data name="Validation_SchemaDoesntContainDiscriminatorPropertyInRequiredFieldList" xml:space="preserve">
+    <value>Schema {0} doesn't contain discriminator property {1} in the required field list.</value>
+  </data>
   <data name="Validation_StringMustBeEmailAddress" xml:space="preserve">
     <value>The string '{0}' MUST be in the format of an email address.</value>
   </data>

src/Microsoft.OpenApi/Validations/Rules/OpenApiSchemaRules.cs

@@ -3,6 +3,8 @@
 
 using Microsoft.OpenApi.Any;
 using Microsoft.OpenApi.Models;
+using Microsoft.OpenApi.Properties;
+using System.Collections.Generic;
 
 namespace Microsoft.OpenApi.Validations.Rules
 {
@@ -55,6 +57,72 @@ public static class OpenApiSchemaRules
                     context.Exit();
                 });
 
+        /// <summary>
+        /// Validates OneOf Discriminator
+        /// </summary>
+        public static ValidationRule<OpenApiSchema> ValidateOneOfDiscriminator =>
+            new ValidationRule<OpenApiSchema>(
+                (context, schema) =>
+                {
+                    // oneOf
+                    context.Enter("oneOf");
+
+                    if (schema.OneOf != null && schema.Discriminator != null)
+                    {
+                        ValidateSchemaListDiscriminator(context, nameof(ValidateOneOfDiscriminator),
+                            schema.OneOf, schema.Discriminator);
+                    }
+
+                    context.Exit();
+                });
+
+        // <summary>
+        /// Validates AnyOf Discriminator
+        /// </summary>
+        public static ValidationRule<OpenApiSchema> ValidateAnyOfDiscriminator =>
+            new ValidationRule<OpenApiSchema>(
+                (context, schema) =>
+                {
+                    // oneOf
+                    context.Enter("anyOf");
+
+                    if (schema.AnyOf != null && schema.Discriminator != null)
+                    {
+                        ValidateSchemaListDiscriminator(context, nameof(ValidateAnyOfDiscriminator),
+                            schema.AnyOf, schema.Discriminator);
+                    }
+
+                    context.Exit();
+                });
+
         // add more rule.
+
+
+        /// <summary>
+        /// Checks if the schemas in the list contain a property with the property name specified by the discriminator.
+        /// </summary>
+        /// <param name="context"></param>
+        /// <param name="ruleName"></param>
+        /// <param name="schemas">OneOf/AnyOf schemas</param>
+        /// <param name="discriminator">discriminator</param>
+        private static void ValidateSchemaListDiscriminator(IValidationContext context, string ruleName,
+                        IList<OpenApiSchema> schemas, OpenApiDiscriminator discriminator)
+        {
+            foreach (var schema in schemas)
+            {
+                if (!schema.Properties.ContainsKey(discriminator.PropertyName))
+                {
+                    context.AddError(new OpenApiValidatorError(ruleName, context.PathString,
+                            string.Format(SRResource.Validation_SchemaDoesntContainDiscriminatorProperty,
+                                        schema.Reference.Id, discriminator.PropertyName)));
+                }
+                if (!schema.Required.Contains(discriminator.PropertyName))
+                {
+                    context.AddError(new OpenApiValidatorError(ruleName, context.PathString,
+                        string.Format(SRResource.Validation_SchemaDoesntContainDiscriminatorPropertyInRequiredFieldList,
+                                        schema.Reference.Id, discriminator.PropertyName)));
+                }
+            }
+        }
     }
 }

test/Microsoft.OpenApi.Readers.Tests/Microsoft.OpenApi.Readers.Tests.csproj

@@ -103,6 +103,8 @@
       <EmbeddedResource Include="V3Tests\Samples\OpenApiDiscriminator\basicDiscriminator.yaml">
         <CopyToOutputDirectory>Never</CopyToOutputDirectory>
       </EmbeddedResource>
+      <EmbeddedResource Include="V3Tests\Samples\OpenApiDiscriminator\invalidAnyOfDiscriminator.yaml" />
+      <EmbeddedResource Include="V3Tests\Samples\OpenApiDiscriminator\invalidOneOfDiscriminator.yaml" />
       <EmbeddedResource Include="V3Tests\Samples\OpenApiDocument\basicDocumentWithMultipleServers.yaml">
         <CopyToOutputDirectory>Never</CopyToOutputDirectory>
       </EmbeddedResource>

test/Microsoft.OpenApi.Readers.Tests/V3Tests/OpenApiDiscriminatorTests.cs

@@ -1,12 +1,16 @@
 // Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT license. 
 
+using System.Collections.Generic;
 using System.IO;
 using System.Linq;
 using FluentAssertions;
 using Microsoft.OpenApi.Models;
+using Microsoft.OpenApi.Properties;
 using Microsoft.OpenApi.Readers.ParseNodes;
 using Microsoft.OpenApi.Readers.V3;
+using Microsoft.OpenApi.Validations;
+using Microsoft.OpenApi.Validations.Rules;
 using SharpYaml.Serialization;
 using Xunit;
 
@@ -47,5 +51,51 @@ public void ParseBasicDiscriminatorShouldSucceed()
                     });
             }
         }
+
+        [Fact]
+        public void OneOfSchemasWithoutDiscriminatorPropertyShouldYieldError()
+        {
+            using (var stream = Resources.GetStream(Path.Combine(SampleFolderPath, "invalidOneOfDiscriminator.yaml")))
+            {
+                var diagnostic = new OpenApiDiagnostic();
+                var reader = new OpenApiStreamReader();
+                var doc = reader.Read(stream, out diagnostic);
+                diagnostic.Errors.ShouldAllBeEquivalentTo(new List<OpenApiError>
+                {
+                    new OpenApiValidatorError(nameof(OpenApiSchemaRules.ValidateOneOfDiscriminator),
+                        "#/paths/~1pets~1{id}/get/responses/200/content/application~1json/schema/oneOf",
+                        string.Format(SRResource.Validation_SchemaDoesntContainDiscriminatorPropertyInRequiredFieldList, "pet1", "petType")),
+
+                    new OpenApiValidatorError(nameof(OpenApiSchemaRules.ValidateOneOfDiscriminator),
+                        "#/paths/~1pets~1{id}/get/responses/200/content/application~1json/schema/oneOf",
+                        string.Format(SRResource.Validation_SchemaDoesntContainDiscriminatorProperty, "pet2", "petType")),
+
+                    new OpenApiValidatorError(nameof(OpenApiSchemaRules.ValidateOneOfDiscriminator), 
+                        "#/paths/~1pets~1{id}/get/responses/200/content/application~1json/schema/oneOf",
+                        string.Format(SRResource.Validation_SchemaDoesntContainDiscriminatorPropertyInRequiredFieldList, "pet2", "petType"))
+                });
+            }
+        }
+
+        [Fact]
+        public void AnyOfSchemasWithoutDiscriminatorPropertyShouldYieldError()
+        {
+            using (var stream = Resources.GetStream(Path.Combine(SampleFolderPath, "invalidAnyOfDiscriminator.yaml")))
+            {
+                var diagnostic = new OpenApiDiagnostic();
+                var reader = new OpenApiStreamReader();
+                var doc = reader.Read(stream, out diagnostic);
+                diagnostic.Errors.ShouldAllBeEquivalentTo(new List<OpenApiError>
+                {
+                    new OpenApiValidatorError(nameof(OpenApiSchemaRules.ValidateAnyOfDiscriminator),
+                        "#/paths/~1pets~1{id}/get/responses/200/content/application~1json/schema/anyOf",
+                        string.Format(SRResource.Validation_SchemaDoesntContainDiscriminatorProperty, "pet2", "petType")),
+
+                    new OpenApiValidatorError(nameof(OpenApiSchemaRules.ValidateAnyOfDiscriminator), 
+                        "#/paths/~1pets~1{id}/get/responses/200/content/application~1json/schema/anyOf",
+                        string.Format(SRResource.Validation_SchemaDoesntContainDiscriminatorPropertyInRequiredFieldList, "pet2", "petType"))
+                });
+            }
+        }
     }
 }

test/Microsoft.OpenApi.Readers.Tests/V3Tests/Samples/OpenApiDiscriminator/invalidAnyOfDiscriminator.yaml

@@ -0,0 +1,61 @@
+openapi: '3.0.0'
+info:
+  version: '1.0.0'
+  title: Petstore - Invalid 'OneOf' discriminator 
+servers:
+    - url: http://petstore.swagger.io/api
+paths:
+  /pets/{id}:
+    get:
+      description: Returns a pet based on a single ID,
+      operationId: findPetById
+      parameters:
+        - name: id
+          in: path
+          description: ID of pet to fetch
+          required: true
+          schema:
+            type: integer
+            format: int64
+      responses:
+        '200':
+          description: pet response
+          content:
+            application/json:
+                schema:
+                  anyOf:
+                    - "$ref": '#/components/schemas/pet1'
+                    - "$ref": '#/components/schemas/pet2'
+                  discriminator:
+                    propertyName: petType
+components:
+    schemas:
+        pet1:
+            type: object
+            required:
+            - id
+            - name
+            - petType
+            properties:
+              id:
+                type: integer
+                format: int64
+              name:
+                type: string
+              tag:
+                type: string
+              petType:
+                type: string
+        pet2:
+            type: object
+            required:
+            - id
+            - name
+            properties:
+              id:
+                type: integer
+                format: int64
+              name:
+                type: string
+              tag:
+                type: string

test/Microsoft.OpenApi.Readers.Tests/V3Tests/Samples/OpenApiDiscriminator/invalidOneOfDiscriminator.yaml

@@ -0,0 +1,60 @@
+openapi: '3.0.0'
+info:
+  version: '1.0.0'
+  title: Petstore - Invalid 'OneOf' discriminator 
+servers:
+    - url: http://petstore.swagger.io/api
+paths:
+  /pets/{id}:
+    get:
+      description: Returns a pet based on a single ID,
+      operationId: findPetById
+      parameters:
+        - name: id
+          in: path
+          description: ID of pet to fetch
+          required: true
+          schema:
+            type: integer
+            format: int64
+      responses:
+        '200':
+          description: pet response
+          content:
+            application/json:
+                schema:
+                  oneOf:
+                    - "$ref": '#/components/schemas/pet1'
+                    - "$ref": '#/components/schemas/pet2'
+                  discriminator:
+                    propertyName: petType
+components:
+    schemas:
+        pet1:
+            type: object
+            required:
+            - id
+            - name
+            properties:
+              id:
+                type: integer
+                format: int64
+              name:
+                type: string
+              tag:
+                type: string
+              petType:
+                type: string
+        pet2:
+            type: object
+            required:
+            - id
+            - name
+            properties:
+              id:
+                type: integer
+                format: int64
+              name:
+                type: string
+              tag:
+                type: string

test/Microsoft.OpenApi.Tests/Validations/ValidationRuleSetTests.cs

@@ -43,7 +43,7 @@ public void DefaultRuleSetPropertyReturnsTheCorrectRules()
             Assert.NotEmpty(rules);
 
             // Update the number if you add new default rule(s).
-            Assert.Equal(20, rules.Count);
+            Assert.Equal(22, rules.Count);
         }
     }
 }