auto-deprecator 2020.5.0
Python decorator and command to automate deprecating components
License: MIT license
Requires Python: >=3.5
Keywords: auto_deprecator

===============
Auto deprecator
===============


.. image:: https://img.shields.io/pypi/v/auto_deprecator.svg
        :target: https://pypi.python.org/pypi/auto-deprecator

.. image:: https://travis-ci.org/auto-deprecator/auto-deprecator.svg
        :target: https://travis-ci.org/auto-deprecator/auto-deprecator

.. image:: https://readthedocs.org/projects/auto-deprecator/badge/?version=latest
        :target: https://auto-deprecator.readthedocs.io/en/latest/?badge=latest
        :alt: Documentation Status

.. image:: https://img.shields.io/pypi/dm/auto-deprecator.svg


Deprecation toolkit in Python

* Free software: MIT license
* Documentation: https://auto-deprecator.readthedocs.io.


How does it work?
-----------------

The library provides the full cycle to deprecate a function in the following ways

.. image:: https://raw.githubusercontent.com/auto-deprecator/auto-deprecator/master/docs/cycle.png

For example, a function called ``old_hello_world`` should be deprecated in the version 2.0.0, while the current version of the library is 1.0.0.

Add a decorator ``deprecate`` above the function like the below can manage the mentioned deprecation cycle.

.. code-block:: python

  from auto_deprecator import deprecate


  @deprecate(expiry='2.0.0', current='1.9.0')
  def old_hello_world():
      return print("Hello world!")


  def hello_world():
      return print("Hello world again!")


You can also suggest the replacing function / method. For details, please refer to the section `Provide hints to users`_.


Warning Stage
#############

Alert the users the deprecation time
====================================

When the user calls the methods or initializes the objects which will be deprecated 
in the next version or on an expected date, the user should receive the warning of
the future deprecation but get the return in success. The default warning handler is to throw a ``DeprecationWarning`` and the handle method can be customized in the section `Customize the deprecation handling`_

.. code-block:: python

  >>> old_hello_world()
  Hello world!
  DeprecationWarning: The function "old_hello_world" will be deprecated on version 2.0.0


Test as if deprecated
=====================

Before the component is deprecated, unit / integration testing should be run
to ensure the deprecation does not break the existing flow. Pass in the environment
variables in the testing to simulate that the version is deployed.

.. code-block:: console

  (bash) hello-world-app
  Hello world!
  DeprecationWarning: The function "old_hello_world" will be deprecated in version 2.0.0

.. code-block:: console

  (bash) DEPRECATED_VERSION=2.0.0 hello-world-app
  Traceback (most recent call last):
   ...
  RuntimeError: The function "old_hello_world" is deprecated in version 2.0.0


Expired Stage
#############

If the current version has reached the function expiry version, 
calling the deprecated function will trigger the exception by default.


.. code-block:: python

  from auto_deprecator import deprecate

  __version__ = '2.0.0'


  @deprecate(expiry='2.0.0', current=__version__)
  def old_hello_world():
      return print("Hello world!")


For example, the above function is called by the downstream
process ``after-hello-world``. The owner of the process is not
aware that the function should be deprecated and replaced by
another function, and the process is crashed by the default
exception. To work around the exception in the production,
before a proper fix is provided, the environment variable
``DEPRECATED_VERSION`` can be injected in the downstream process.


.. code-block:: bash

  DEPRECATED_VERSION=1.9 after-hello-world


Cleaning Stage
##############


Automatic deprecation before release
====================================

Deprecating the functions is no longer a manual work. Every time before release,
run the command ``auto-deprecate`` to remove the functions deprecated in the coming
version.

.. code-block:: console

  $ auto-deprecate hello_world.py --version 2.0.0

The command removes the function ``old_hello_world`` from the source codes as the expiry version is 2.0.0. Also, if the source file does not require to import the ``auto-deprecate`` anymore (as all the functions have already been deprecated), the import line will be removed as well.

.. code-block:: console

  $ git difftool -y -x sdiff
  from auto_deprecator import deprecate                         <
                                                                <
                                                                <
  @deprecate(expiry='2.0.0', current='1.9.0')                   <
  def old_hello_world():                                        <
      return print("Hello world!")                              <
                                                                <
                                                                <
  def hello_world():                                              def hello_world():
      return print("Hello world again!")                        /     return print("Hello world again!")


The function with a comment line to state the expiry version is
another way to inform the script ``auto-deprecate`` to remove the
part of the code when it is expired. For example,

.. code-block:: python

    def old_hello_world():
        # auto-deprecate: expiry=2.0.0
        print('hello world')

For the details of the comment hints, please refer to the section `Auto deprecation hints in comments`_.

Installation
------------

The library can be easily installed with pip

.. code-block:: console

  pip install auto-deprecator



Alternative Installation
------------------------

If the auto-deprecator is included and the functions are
well deprecated (following the whole cycle mentioned above),
your software does not need auto-deprecator anymore. For
developers who are not comfortable to include a library not
always in use as a dependency, they can just clone the source
code into your project instead.

For example, your Python project contains a module called
"utils" to maintain all the utility functions.

.. code-block:: console

  .
  ├── setup.py
  └── test_py_project
      ├── cli.py
      ├── __init__.py
      ├── test_py_project.py
      └── utils
          └── __init__.py

With the bash command "curl",

.. code-block:: console

  curl https://raw.githubusercontent.com/auto-deprecator/auto-deprecator/develop/auto_deprecator/__init__.py -o $DEST

the source code of auto-deprecator can be cloned into the
target directory, i.e. "test_py_project/utils" in the example

.. code-block:: console

  curl https://raw.githubusercontent.com/auto-deprecator/auto-deprecator/develop/auto_deprecator/__init__.py -o test_py_project/utils/auto_deprecator.py


Features
--------

Provide hints to users
######################

Provide the parameter "relocate", the warning / error message will inform the user about 
the relocated method.

.. code-block:: python

  @deprecate(expiry='2.1.0', current='2.0.0', relocate='new_compute_method')
  def compute_method():
      return 'hello world'

.. code-block:: python

  >>> old_hello_world()
  Hello world!
  DeprecationWarning: The function "old_hello_world" will be deprecated on version 2.0.0..
                      Please use method / function "new_compute_method".


Import current version from module name
#######################################

Instead of importing the version (``__version__``) in the module,

.. code-block:: python

  from your_package import __version__

  @deprecate(expiry='2.1.0', current=__version__)
  def compute_method():
      return 'hello world'

specifying the module name, which includes the version attribute, can
help maintain the source code in a clean manner.

.. code-block:: python

  @deprecate(expiry='2.1.0', version_module='your_package')
  def compute_method():
      return 'hello world'

Especially if the function is removed by the action ``auto-deprecate``,
the unused import will not be left in the module.

Customize the deprecation handling
##################################

By default, the ``deprecate`` decorator raise ``DeprecationWarning`` for the future expiry and ``RuntimeError`` on the expiration. The behavior can be modified so as to fit in the infrastructure / production environment.

For example, the ``DeprecationWarning`` can be replaced by a simple print out by injecting a callable function into the parameter ``warn_handler``.

.. code-block:: python

  @deprecate(expiry='2.1.0', current='2.0.0', warn_handler=print)
  def compute_method():
      return 'hello world'


Same for injecting a callable function into the parameter ``error_handler``, the behavior is replaced if the function is deprecated.


Auto deprecation hints in comments
##################################

The auto deprecation script handles not only the expiry parts wrapped by the decorator, but also those stated with comments.
The comment line in the format ``# auto-deprecate: expiry=<version>``
in the scope of the function or class is treated same as the
decorator hints ``@deprecate(expiry="version", ...)``.

For example, the below function will be removed

.. code-block:: python

    # hello_world.py


    def old_hello_world():
        # auto-deprecate: expiry=2.0.0
        print('hello world')

when the script is called with current version greater than 2.0.0

.. code-block:: console

    $ auto-deprecate hello_world.py --version 2.1.0


=======
History
=======

2020.4.0 (2020-04-23)
---------------------

* Support deprecation hints in comments
* Simplify the project architecture

2020.3.0 (2020-04-11)
---------------------

* Support automatic deprecation in the directory
* Support customizing the deprecation handler

2020.2.0 (2020-02-11)
---------------------

* Introduce parameter version_module in the deprecate decorator, to
  import the version dynamically
* Removed magic version import

2010.1.0, 2010.1.1, 2010.1.2 (2020-01-21)
-----------------------------------------

* Support alerting the users the deprecate version
* Support testing with environment variables
* Support automatically deprecate the expiry source code