Fix exceptions when loading OAS documents with extensions on paths and responses

[alasdairhurst]

Fixes loading and validation for Swagger which has extensions on the path and response level. Previously it would throw errors when trying to parse the value of an extension as a path or response.

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[alasdairhurst]

This fixes #198

[alasdairhurst]

@whitlockjc my "evil" swagger document that I use for testing compatibility loads a bit further with this fix in place. Here it is if you want to test it:

{
	"swagger": "2.0",
	"x-an-extension-null": null,
	"x-an-extension-primitive": 1,
	"x-an-extension-array": [],
	"x-an-extension-object": {},
	"host": "localhost:8080",
	"basePath": "/test",
	"schemes": [
		"http",
		"https",
		"ws",
		"wss"
	],
	"consumes": [
		"application/json"
	],
	"produces": [
		"application/json"
	],
	"info": {
		"version": "0.0.0",
		"title": "Thing API",
		"contact": {
			"name": "Axway Person",
			"url": "http://www.axway.com",
			"email": "[email protected]",
			"x-an-extension-null": null,
			"x-an-extension-primitive": 1,
			"x-an-extension-array": [],
			"x-an-extension-object": {}
		},
		"license": {
			"name": "FREE",
			"url": "http://www.axway.com",
			"x-an-extension-null": null,
			"x-an-extension-primitive": 1,
			"x-an-extension-array": [],
			"x-an-extension-object": {}
		},
		"x-an-extension-null": null,
		"x-an-extension-primitive": 1,
		"x-an-extension-array": [],
		"x-an-extension-object": {}
	},
	"parameters": {
		"apiKey": {
			"in": "query",
			"name": "apiKey",
			"type": "string",
			"required": true
		},
		"name": {
			"name": "name",
			"enum": [
				"foo",
				"bar",
				"baz"
			],
			"in": "query",
			"type": "string",
			"format": "password",
			"allowEmptyValue": true
		},
		"fooArr": {
			"name": "fooArr",
			"in": "query",
			"type": "array",
			"description": "an array of array of strings no bigger than 10 characters beginning with h y or m",
			"collectionFormat": "pipes",
			"uniqueItems": true,
			"default": [
				[
					"hello",
					"you"
				],
				[
					"me"
				]
			],
			"items": {
				"type": "array",
				"collectionFormat": "csv",
				"default": [
					"hello",
					"me"
				],
				"items": {
					"type": "string",
					"maxLength": 10,
					"minLength": 2,
					"pattern": "^[hmy]"
				}
			}
		},
		"barInt": {
			"x-an-extension-null": null,
			"x-an-extension-primitive": 1,
			"x-an-extension-array": [],
			"x-an-extension-object": {},
			"in": "query",
			"description": "an integer which is a multiple of 5 but bigger than 5 and no bigger than 100",
			"name": "barInt",
			"type": "integer",
			"multipleOf": 5,
			"maximum": 100,
			"exclusiveMaximum": false,
			"minimum": 5,
			"exclusiveMinimum": true
		}
	},
	"paths": {
		"x-an-extension-null": null,
		"x-an-extension-primitive": 1,
		"x-an-extension-array": [],
		"x-an-extension-object": {
			"get": {
				"description": "this is an x- extension and not a path/method",
				"responses": {
					"default": {
						"description": "too lazy to make a 200"
					}
				}
			}
		},
		"x-not-a-path-but-used-in-ref": {
			"get": {
				"description": "this is a method used by a path which isn't 'x-not-a-path-but-used-in-ref'",
				"responses": {
					"default": {
						"description": "too lazy to make a 200"
					}
				}
			}
		},
		"/thingEmpty": {},
		"/thingyref": {
			"$ref": "#/paths/x-not-a-path-but-used-in-ref"
		},
		"/thing": {
			"parameters": [
				{
					"$ref": "#/parameters/apiKey"
				}
			],
			"get": {
				"x-an-extension-null": null,
				"x-an-extension-primitive": 1,
				"x-an-extension-array": [],
				"x-an-extension-object": {},
				"description": "has no operation id, no parameters",
				"responses": {
					"default": {
						"description": "too lazy to make a 200"
					}
				}
			},
			"patch": {
				"x-an-extension-null": null,
				"x-an-extension-primitive": 1,
				"x-an-extension-array": [],
				"x-an-extension-object": {},
				"description": "updates name",
				"parameters": [
					{
						"name": "name",
						"in": "query",
						"type": "string"
					},
					{
						"name": "apiKey",
						"in": "query",
						"type": "number",
						"description": "Overrides the path item parameters"
					}
				],
				"responses": {
					"204": {
						"description": "done"
					}
				}
			},
			"delete": {
				"x-an-extension-null": null,
				"x-an-extension-primitive": 1,
				"x-an-extension-array": [],
				"x-an-extension-object": {},
				"tags": [
					"foo",
					"bar",
					"baz"
				],
				"summary": "interesting endpoint which deletes something for the sake of it.",
				"externalDocs": {
					"description": "foo",
					"url": "http://www.axway.com",
					"x-an-extension-null": null,
					"x-an-extension-primitive": 1,
					"x-an-extension-array": [],
					"x-an-extension-object": {}
				},
				"operationId": "deleteNameUnique",
				"consumes": [
					"application/custom+json"
				],
				"produces": [
					"application/custom+json"
				],
				"description": "deletes name",
				"parameters": [
					{
						"$ref": "#/parameters/name"
					},
					{
						"$ref": "#/parameters/fooArr"
					},
					{
						"$ref": "#/parameters/barInt"
					}
				],
				"responses": {
					"201": {
						"description": "done"
					}
				}
			},
			"put": {
				"x-an-extension-null": null,
				"x-an-extension-primitive": 1,
				"x-an-extension-array": [],
				"x-an-extension-object": {},
				"operationId": "uploadThing",
				"consumes": [
					"multipart/form-data"
				],
				"parameters": [
					{
						"x-an-extension-null": null,
						"x-an-extension-primitive": 1,
						"x-an-extension-array": [],
						"x-an-extension-object": {},
						"name": "thing",
						"in": "formData",
						"description": "file to upload",
						"required": true,
						"type": "file"
					}
				],
				"responses": {
					"default": {
						"description": "Updated"
					}
				}
			},
			"post": {
				"x-an-extension-null": null,
				"x-an-extension-primitive": 1,
				"x-an-extension-array": [],
				"x-an-extension-object": {},
				"operationId": "upsert",
				"parameters": [
					{
						"name": "thing",
						"in": "body",
						"schema": {
							"$ref": "#/definitions/wannaBeThing"
						}
					}
				],
				"schemes": [
					"http",
					"https"
				],
				"deprecated": true,
				"responses": {
					"200": {
						"x-an-extension-null": null,
						"x-an-extension-primitive": 1,
						"x-an-extension-array": [],
						"x-an-extension-object": {},
						"description": "Updated",
						"schema": {
							"$ref": "#/definitions/thing"
						},
						"headers": {
							"Location": {
								"x-an-extension-null": null,
								"x-an-extension-primitive": 1,
								"x-an-extension-array": [],
								"x-an-extension-object": {},
								"type": "string",
								"description": "Location of new resource"
							}
						},
						"examples": {
							"application/json": {
								"name": "Puma",
								"id": "Dog"
							}
						}
					},
					"201": {
						"description": "Created",
						"headers": {
							"Location": {
								"type": "string",
								"description": "Location of new resource"
							}
						}
					},
					"204": {
						"description": "Updated no content"
					},
					"400": {
						"description": "Bad request",
						"schema": {
							"$ref": "#/definitions/error"
						}
					},
					"500": {
						"description": "Server error",
						"schema": {
							"$ref": "#/definitions/serverError"
						}
					},
					"501": {
						"description": "Inline schema",
						"schema": {
							"type": "object",
							"description": "why not"
						}
					},
					"x-an-extension-null": null,
					"x-an-extension-primitive": 1,
					"x-an-extension-array": [],
					"x-an-extension-object": {},
					"default": {
						"$ref": "#/responses/serverError"
					}
				}
			}
		}
	},
	"responses": {
		"serverError": {
			"description": "Server error",
			"schema": {
				"$ref": "#/definitions/serverError"
			}
		}
	},
	"definitions": {
		"geo": {
			"description": "A geographical coordinate",
			"type": "object",
			"properties": {
				"latitude": {
					"type": "number"
				},
				"longitude": {
					"type": "number"
				}
			}
		},
		"wannaBeThing": {
			"x-an-extension-null": null,
			"x-an-extension-primitive": 1,
			"x-an-extension-array": [],
			"x-an-extension-object": {},
			"discriminator": "name",
			"type": "object",
			"properties": {
				"name": {
					"type": "string"
				}
			},
			"required": [
				"name"
			]
		},
		"thing": {
			"x-an-extension-null": null,
			"x-an-extension-primitive": 1,
			"x-an-extension-array": [],
			"x-an-extension-object": {},
			"type": "object",
			"properties": {
				"id": {
					"type": "number"
				},
				"name": {
					"type": "string"
				}
			},
			"required": [
				"id",
				"name"
			]
		},
		"serverError": {
			"x-an-extension-null": null,
			"x-an-extension-primitive": 1,
			"x-an-extension-array": [],
			"x-an-extension-object": {},
			"type": "object",
			"properties": {
				"message": {
					"type": "string"
				},
				"location": {
					"$ref": "#/definitions/geo"
				}
			},
			"required": [
				"message"
			]
		},
		"error": {
			"x-an-extension-null": null,
			"x-an-extension-primitive": 1,
			"x-an-extension-array": [],
			"x-an-extension-object": {},
			"type": "object",
			"properties": {
				"messages": {
					"type": "array",
					"items": {
						"type": "string"
					}
				}
			},
			"required": [
				"messages"
			]
		}
	}
}