httpproblem 0.2.0
Utility library to work with RFC7807 Problem Details for HTTP APIs
License: MIT
Keywords: rfc7807 problem http json

python-httpproblem
==================

Utility library to work with `RFC7807 Problem Details for HTTP
APIs <https://tools.ietf.org/html/rfc7807>`__.

|Build Status| |sonar-quality-gate| |sonar-coverage| |sonar-bugs|
|sonar-vulnerabilities|

This library is very light-weight, with no external dependencies,
fully-tested and works with both Python 2 and Python 3. It has special
support for `AWS lambda proxy integration output
format <https://docs.aws.amazon.com/apigateway/latest/developerguide/set-up-lambda-proxy-integrations.html#api-gateway-simple-proxy-for-lambda-output-format>`__
but it should be easy to map to any other format or framework. Currently
only JSON serialization is supported.

Installation
============

::

    pip install httpproblem

Usage
=====

Build a Problem dict
--------------------

The ``problem()`` function that can be used to build a dict with the
problem fields.

.. code:: python

    >>> pprint(problem(httplib.BAD_REQUEST, 'You do not have enough credit.', 'Your current balance is 30, but that costs 50.', '/account/12345/msgs/abc'))
    {'detail': 'Your current balance is 30, but that costs 50.',
     'status': 400,
     'title': 'You do not have enough credit.',
     'type': '/account/12345/msgs/abc'}

You can also use problem extensions

.. code:: python

    >>> pprint(problem(httplib.BAD_REQUEST, 'You do not have enough credit.', 'Your current balance is 30, but that costs 50.', '/account/12345/msgs/abc', balance=30, accounts=['/account/12345','/account/67890']))
    {'accounts': ['/account/12345', '/account/67890'],
     'balance': 30,
     'detail': 'Your current balance is 30, but that costs 50.',
     'status': 400,
     'title': 'You do not have enough credit.',
     'type': '/account/12345/msgs/abc'}

As specified by `Predefined Problem
Types <https://tools.ietf.org/html/rfc7807#section-4.2>`__:

    The “about:blank” URI, when used as a problem type, indicates that
    the problem has no additional semantics beyond that of the HTTP
    status code.

..

    When “about:blank” is used, the title SHOULD be the same as the
    recommended HTTP status phrase for that code (e.g., “Not Found” for
    404, and so on), although it MAY be localized to suit client
    preferences (expressed with the Accept-Language request header).

So if this library will automatically fill the title field if the type
is not present or ``about:blank``.

.. code:: python

    >>> problem(404)
    {'status': 404, 'title': 'Not Found'}
    >>> problem(httplib.BAD_REQUEST, type='about:blank')
    {'status': 400, 'type': 'about:blank', 'title': 'Bad Request'}

Build a Problem HTTP response
-----------------------------

The ``problem_http_response()`` function helps to build HTTP responses
using the format used by the AWS lambda proxy integration. The method
will automatically fill the ``Content-Type`` header with
``application/problem+json`` and the HTTP response code with the status.

.. code:: python

    >>> pprint(problem_http_response(httplib.BAD_REQUEST))
    {'body': '{"status": 400, "type": "about:blank", "title": "Bad Request"}',
     'headers': {'Content-Type': 'application/problem+json'},
     'statusCode': 400}

You can map this to other frameworks. For instance for Flask (or
Werkzeug):

.. code:: python

    >>> problem = problem_http_response(400)
    >>> print(flask.Response(problem['body'], status=problem['statusCode'], headers=problem['headers']))
    <Response 39 bytes [400 BAD REQUEST]>

By default, ``json.dumps`` is used to serialize into JSON. This can be
changed by using the ``set_serialize_function``

::

    >>> httpproblem.set_serialize_method(lambda data: json.dumps(data, indent=4))
    >>> print(problem_http_response(400)['body'])
    {
        "status": 400,
        "title": "Bad Request"
    }

Raise a Problem exception
-------------------------

The ``Problem`` exception class can be used to simplify the error
management with try/except. The class has methods to convert it to a
Problem dict or HTTP response.

.. code:: python

    >>> try:
    ...     raise Problem(httplib.BAD_REQUEST)
    ... except Problem as e:
    ...     print(e.to_dict())
    ...
    {'status': 400, 'title': 'Bad Request'}

The ``to_dict`` and ``to_http_response`` take a ``with_traceback``
argument that can be used to include the traceback. You can also set it
globally with the ``activate_traceback()`` function. For security
reasons, the default is to not include the traceback and it is
recommended to not activate it in production.

.. code:: python

    >>> # Add traceback by call argument
    >>> try:
    ...     raise Problem(httplib.BAD_REQUEST)
    ... except Problem as e:
    ...     pprint(e.to_dict(with_traceback=True))
    ...
    {'status': 400,
     'title': 'Bad Request',
     'traceback': 'Traceback (most recent call last):\n  File "<stdin>", line 2, in <module>\nProblem: {\'status\': 400, \'title\': \'Bad Request\'}\n'}
    >>>
    >>> # Add traceback globally
    >>> httpproblem.activate_traceback()
    >>> try:
    ...     raise Problem(httplib.BAD_REQUEST)
    ... except Problem as e:
    ...     pprint(e.to_dict())
    ...
    {'status': 400,
     'title': 'Bad Request',
     'traceback': 'Traceback (most recent call last):\n  File "<stdin>", line 2, in <module>\nProblem: {\'status\': 400, \'title\': \'Bad Request\'}\n'}

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