chore(library): add v3 contains extension deserialization

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: baywet

src/Microsoft.OpenApi/Reader/V3/OpenApiSchemaDeserializer.cs

@@ -316,6 +316,32 @@ internal static partial class OpenApiV3Deserializer
                 OpenApiConstants.ContentSchemaExtension,
                 (o, n, doc, c) => o.ContentSchema = LoadSchema(n, doc, c)
             },
+            {
+                OpenApiConstants.ContainsExtension,
+                (o, n, doc, c) => o.Contains = LoadSchema(n, doc, c)
+            },
+            {
+                OpenApiConstants.MaxContainsExtension,
+                (o, n, _, _) =>
+                {
+                    var maxContains = n.GetScalarValue();
+                    if (maxContains != null)
+                    {
+                        o.MaxContains = uint.Parse(maxContains, CultureInfo.InvariantCulture);
+                    }
+                }
+            },
+            {
+                OpenApiConstants.MinContainsExtension,
+                (o, n, _, _) =>
+                {
+                    var minContains = n.GetScalarValue();
+                    if (minContains != null)
+                    {
+                        o.MinContains = uint.Parse(minContains, CultureInfo.InvariantCulture);
+                    }
+                }
+            },
             {
                 OpenApiConstants.PropertyNamesExtension,
                 (o, n, doc, c) => o.PropertyNames = LoadSchema(n, doc, c)

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

@@ -189,6 +189,11 @@ public void ParseSchemaWithOaiCompatibilityKeywordsShouldSucceed()
   ""x-jsonschema-contentSchema"": {
     ""type"": ""array""
   },
+  ""x-jsonschema-contains"": {
+    ""type"": ""string""
+  },
+  ""x-jsonschema-maxContains"": 5,
+  ""x-jsonschema-minContains"": 1,
   ""x-jsonschema-propertyNames"": {
     ""pattern"": ""^[a-z]+$""
   },
@@ -216,6 +221,9 @@ public void ParseSchemaWithOaiCompatibilityKeywordsShouldSucceed()
             Assert.Equal("base64", missingProperties.ContentEncoding);
             Assert.Equal("application/jwt", missingProperties.ContentMediaType);
             Assert.Equal(JsonSchemaType.Array, missingProperties.ContentSchema?.Type);
+            Assert.Equal(JsonSchemaType.String, missingProperties.Contains?.Type);
+            Assert.Equal((uint?)5, missingProperties.MaxContains);
+            Assert.Equal((uint?)1, missingProperties.MinContains);
             Assert.Equal("^[a-z]+$", missingProperties.PropertyNames?.Pattern);
             Assert.Equal(JsonSchemaType.String, missingProperties.DependentSchemas?["token"].Type);
             Assert.NotNull(missingProperties.If?.Required);

test/Microsoft.OpenApi.Tests/Models/OpenApiSchemaTests.cs

@@ -1817,6 +1817,42 @@ public void DeserializePatternPropertiesExtensionInV3AssignsPatternPropertiesPro
             Assert.True(schema.Extensions is null || !schema.Extensions.ContainsKey("x-jsonschema-patternProperties"));
         }
 
+        [Fact]
+        public void DeserializeContainsExtensionsInV3AssignsContainsProperties()
+        {
+            var jsonContent = """
+            {
+              "openapi": "3.0.0",
+              "info": { "title": "Test", "version": "1.0" },
+              "paths": {},
+              "components": {
+                "schemas": {
+                  "TestSchema": {
+                    "type": "array",
+                    "x-jsonschema-contains": {
+                      "type": "string"
+                    },
+                    "x-jsonschema-maxContains": 5,
+                    "x-jsonschema-minContains": 1
+                  }
+                }
+              }
+            }
+            """;
+
+            var readResult = OpenApiDocument.Parse(jsonContent, "json");
+
+            Assert.Empty(readResult.Diagnostic.Errors);
+            var schema = readResult.Document.Components.Schemas["TestSchema"];
+            var missingProperties = Assert.IsAssignableFrom<IOpenApiSchemaMissingProperties>(schema);
+            Assert.Equal(JsonSchemaType.String, missingProperties.Contains?.Type);
+            Assert.Equal((uint?)5, missingProperties.MaxContains);
+            Assert.Equal((uint?)1, missingProperties.MinContains);
+            Assert.True(schema.Extensions is null || !schema.Extensions.ContainsKey(OpenApiConstants.ContainsExtension));
+            Assert.True(schema.Extensions is null || !schema.Extensions.ContainsKey(OpenApiConstants.MaxContainsExtension));
+            Assert.True(schema.Extensions is null || !schema.Extensions.ContainsKey(OpenApiConstants.MinContainsExtension));
+        }
+
         internal class SchemaVisitor : OpenApiVisitorBase
         {
             public List<string> Titles = new();