Collapsed components that are references

src/Microsoft.OpenApi.Readers/ParseNodes/MapNode.cs

@@ -100,11 +100,15 @@ public override Dictionary<string, T> CreateMapWithReference<T>(
                     {
                         return null;  // Body Parameters shouldn't be converted to Parameters
                     }
-                    entry.value.Reference = new OpenApiReference()
+                    // If the component isn't a reference to another component, then point it to itself.
+                    if (entry.value.Reference == null)
                     {
-                        Type = referenceType,
-                        Id = entry.key
-                    };
+                        entry.value.Reference = new OpenApiReference()
+                        {
+                            Type = referenceType,
+                            Id = entry.key
+                        };
+                    }
                     return entry;
                 }
                 );

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

@@ -12,6 +12,9 @@
         <SignAssembly>true</SignAssembly>
         <AssemblyOriginatorKeyFile>..\..\src\Microsoft.OpenApi.snk</AssemblyOriginatorKeyFile>
     </PropertyGroup>
+    <ItemGroup>
+      <None Remove="V2Tests\Samples\ComponentRootReference.json" />
+    </ItemGroup>
     <ItemGroup>
       <EmbeddedResource Include="OpenApiReaderTests\Samples\unsupported.v1.yaml">
         <CopyToOutputDirectory>Never</CopyToOutputDirectory>
@@ -25,6 +28,9 @@
       <EmbeddedResource Include="V2Tests\Samples\basic.v3.yaml">
         <CopyToOutputDirectory>Never</CopyToOutputDirectory>
       </EmbeddedResource>
+      <EmbeddedResource Include="V2Tests\Samples\ComponentRootReference.json">
+        <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+      </EmbeddedResource>
       <EmbeddedResource Include="V2Tests\Samples\minimal.v2.yaml">
         <CopyToOutputDirectory>Never</CopyToOutputDirectory>
       </EmbeddedResource>

test/Microsoft.OpenApi.Readers.Tests/V2Tests/OpenApiDocumentTests.cs

@@ -419,5 +419,24 @@ public void ShouldAssignSchemaToAllResponses()
                 xml.Schema.ShouldBeEquivalentTo(targetSchema);
             }
         }
+
+
+        [Fact]
+        public void ShouldAllowComponentsThatJustContainAReference()
+        {
+            using (var stream = Resources.GetStream(Path.Combine(SampleFolderPath, "ComponentRootReference.json")))
+            {
+                OpenApiStreamReader reader = new OpenApiStreamReader();
+                OpenApiDocument doc = reader.Read(stream, out OpenApiDiagnostic diags);
+                OpenApiSchema schema1 = doc.Components.Schemas["AllPets"];
+                Assert.False(schema1.UnresolvedReference);
+                OpenApiSchema schema2 = (OpenApiSchema)doc.ResolveReference(schema1.Reference);
+                if (schema2.UnresolvedReference && schema1.Reference.Id == schema2.Reference.Id)
+                {
+                    // detected a cycle - this code gets triggered
+                    Assert.True(false, "A cycle should not be detected");
+                }
+            }
+        }
     }
 }

test/Microsoft.OpenApi.Readers.Tests/V2Tests/Samples/ComponentRootReference.json

@@ -0,0 +1,178 @@
+{
+	"openapi": "3.0.0",
+	"info": {
+		"version": "1.0.0",
+		"title": "Swagger Petstore",
+		"license": {
+			"name": "MIT"
+		}
+	},
+	"servers": [
+		{
+			"url": "http://petstore.swagger.io/v1"
+		}
+	],
+	"paths": {
+		"/pets": {
+			"get": {
+				"summary": "List all pets",
+				"operationId": "listPets",
+				"tags": [
+					"pets"
+				],
+				"parameters": [
+					{
+						"name": "limit",
+						"in": "query",
+						"description": "How many items to return at one time (max 100)",
+						"required": false,
+						"schema": {
+							"type": "integer",
+							"format": "int32"
+						}
+					}
+				],
+				"responses": {
+					"200": {
+						"description": "A paged array of pets",
+						"headers": {
+							"x-next": {
+								"description": "A link to the next page of responses",
+								"schema": {
+									"type": "string"
+								}
+							}
+						},
+						"content": {
+							"application/json": {
+								"schema": {
+									"$ref": "#/components/schemas/AllPets"
+								}
+							}
+						}
+					},
+					"default": {
+						"description": "unexpected error",
+						"content": {
+							"application/json": {
+								"schema": {
+									"$ref": "#/components/schemas/Error"
+								}
+							}
+						}
+					}
+				}
+			},
+			"post": {
+				"summary": "Create a pet",
+				"operationId": "createPets",
+				"tags": [
+					"pets"
+				],
+				"responses": {
+					"201": {
+						"description": "Null response"
+					},
+					"default": {
+						"description": "unexpected error",
+						"content": {
+							"application/json": {
+								"schema": {
+									"$ref": "#/components/schemas/Error"
+								}
+							}
+						}
+					}
+				}
+			}
+		},
+		"/pets/{petId}": {
+			"get": {
+				"summary": "Info for a specific pet",
+				"operationId": "showPetById",
+				"tags": [
+					"pets"
+				],
+				"parameters": [
+					{
+						"name": "petId",
+						"in": "path",
+						"required": true,
+						"description": "The id of the pet to retrieve",
+						"schema": {
+							"type": "string"
+						}
+					}
+				],
+				"responses": {
+					"200": {
+						"description": "Expected response to a valid request",
+						"content": {
+							"application/json": {
+								"schema": {
+									"$ref": "#/components/schemas/Pets"
+								}
+							}
+						}
+					},
+					"default": {
+						"description": "unexpected error",
+						"content": {
+							"application/json": {
+								"schema": {
+									"$ref": "#/components/schemas/Error"
+								}
+							}
+						}
+					}
+				}
+			}
+		}
+	},
+	"components": {
+		"schemas": {
+			"Pet": {
+				"required": [
+					"id",
+					"name"
+				],
+				"properties": {
+					"id": {
+						"type": "integer",
+						"format": "int64"
+					},
+					"name": {
+						"type": "string"
+					},
+					"tag": {
+						"type": "string"
+					}
+				}
+			},
+			"Pets": {
+				"type": "array",
+				"items": {
+					"$ref": "#/components/schemas/Pet"
+				}
+			},
+			"AllPets": {
+				"$ref": "#/components/schemas/Pets"
+			},
+			"Error": {
+				"required": [
+					"code",
+					"message"
+				],
+				"properties": {
+					"code": {
+						"type": "integer",
+						"format": "int32"
+					},
+					"message": {
+						"type": "string"
+					}
+				}
+			}
+		}
+	}
+}