Swagger-spec-validator

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- Add warning when using ``$ref`` together with other properties - PR 107

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- Disallow multiple types in schema definitions. See `OpenAPI458 <https://github.com/OAI/OpenAPI-Specification/issues/458>`_ for context - PR #106

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- Fix urlopen issue on Windows platform. Issue 99, PR 101

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- Ensure that inline models are validated - 97
- Ensure that parameters are validated - 97
- Validation of defaults set to None is skipped if x-nullable is set - 97

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- Add support for reading YAML files - 74
- Make sure operationIds are unique within the same tag - 93
- Validate that array models in the top-level definitions have an ``items`` property (validation for array models in other places will come in a future release) - 95
- Responses (the mapping of HTTP status codes to Response objects) cannot be a reference - 92
- ``$ref`` values need to be strings - 83. Thanks ceridwen for your contribution!
- Ensure that default values are compliant with the spec - 82
- More helpful error message when encountering unresolvable path params - 72. Thanks daym for your contribution!

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- Properly validate polymorphic objects - 68