Upgrading To Newer Releases
===========================

Click attempts the highest level of backwards compatibility but sometimes
this is not entirely possible.  In case we need to break backwards
compatibility this document gives you information about how to upgrade or
handle backwards compatibility properly.

.. _upgrade-to-7.0:

Upgrading to 7.0
----------------

Commands that take their name from the decorated function now replace
underscores with dashes. For example, the Python function ``run_server``
will get the command name ``run-server`` now. There are a few options
to address this:

-   To continue with the new behavior, pin your dependency to
    ``Click>=7`` and update any documentation to use dashes.
-   To keep existing behavior, add an explicit command name with
    underscores, like ``@click.command("run_server")``.
-   To try a name with dashes if the name with underscores was not
    found, pass a ``token_normalize_func`` to the context:

    .. code-block:: python

        def normalize(name):
            return name.replace("_", "-")

        @click.group(context_settings={"token_normalize_func": normalize})
        def group():
            ...

        @group.command()
        def run_server():
            ...


.. _upgrade-to-3.2:

Upgrading to 3.2
----------------

Click 3.2 had to perform two changes to multi commands which were
triggered by a change between Click 2 and Click 3 that had bigger
consequences than anticipated.

Context Invokes
```````````````

Click 3.2 contains a fix for the :meth:`Context.invoke` function when used
with other commands.  The original intention of this function was to
invoke the other command as as if it came from the command line when it
was passed a context object instead of a function.  This use was only
documented in a single place in the documentation before and there was no
proper explanation for the method in the API documentation.

The core issue is that before 3.2 this call worked against intentions::

    ctx.invoke(other_command, 'arg1', 'arg2')

This was never intended to work as it does not allow Click to operate on
the parameters.  Given that this pattern was never documented and ill
intended the decision was made to change this behavior in a bugfix release
before it spreads by accident and developers depend on it.

The correct invocation for the above command is the following::

    ctx.invoke(other_command, name_of_arg1='arg1', name_of_arg2='arg2')

This also allowed us to fix the issue that defaults were not handled
properly by this function.

Multicommand Chaining API
`````````````````````````

Click 3 introduced multicommand chaining.  This required a change in how
Click internally dispatches.  Unfortunately this change was not correctly
implemented and it appeared that it was possible to provide an API that
can inform the super command about all the subcommands that will be
invoked.

This assumption however does not work with one of the API guarantees that
have been given in the past.  As such this functionality has been removed
in 3.2 as it was already broken.  Instead the accidentally broken
functionality of the :attr:`Context.invoked_subcommand` attribute was
restored.

If you do require the know which exact commands will be invoked there are
different ways to cope with this.  The first one is to let the subcommands
all return functions and then to invoke the functions in a
:meth:`Context.result_callback`.


.. _upgrade-to-2.0:

Upgrading to 2.0
----------------

Click 2.0 has one breaking change which is the signature for parameter
callbacks.  Before 2.0, the callback was invoked with ``(ctx, value)``
whereas now it's ``(ctx, param, value)``.  This change was necessary as it
otherwise made reusing callbacks too complicated.

To ease the transition Click will still accept old callbacks.  Starting
with Click 3.0 it will start to issue a warning to stderr to encourage you
to upgrade.

In case you want to support both Click 1.0 and Click 2.0, you can make a
simple decorator that adjusts the signatures::

    import click
    from functools import update_wrapper

    def compatcallback(f):
        # Click 1.0 does not have a version string stored, so we need to
        # use getattr here to be safe.
        if getattr(click, '__version__', '0.0') >= '2.0':
            return f
        return update_wrapper(lambda ctx, value: f(ctx, None, value), f)

With that helper you can then write something like this::

    @compatcallback
    def callback(ctx, param, value):
        return value.upper()

Note that because Click 1.0 did not pass a parameter, the `param` argument
here would be `None`, so a compatibility callback could not use that
argument.
