docs/source/whatsnew/development.rst

=====================
 Development version
=====================

This document describes in-flight development work.

.. warning::

    Please do not edit this file by hand (doing so will likely cause merge
    conflicts for other Pull Requests). Instead, create a new file in the
    `docs/source/whatsnew/pr` folder


Released .... ...., 2019


Need to be updated:

.. toctree::
   :maxdepth: 2
   :glob:

   pr/*

IPython 8.0 is bringing a large number of new features and improvements to both the
user of the terminal and of the kernel via Jupyter. The removal of compatibility
with older version of Python is also the opportunity to do a couple of
performance improvement in particular with respect to startup time.

This release contains 250+ Pull requests, in addition to many of the features
and backports that have made it to the 7.x branch.

We removed almost all features, arguments, functions, and modules that were
marked as deprecated between IPython 1.0 and 5.0 and before. As reminder 5.0 was
released in 2016, and 1.0 in 2013. Last release of the 5 branch was 5.10.0, in
may 2020. The few remaining deprecated features have better deprecation warnings
or errors.

There are many change in IPython 8.0 will will try to describe subsequently,


The first on is the integration of the ``stack_data`` package;
which provide smarter information in traceback; in particular it will highlight
the AST node where an error occurs which can help to quickly narrow down errors.

For example in the following snippet::

    def foo(i):
        x = [[[0]]]
        return x[0][i][0]


    def bar():
        return foo(0) + foo(
            1
        ) + foo(2)


Calling ``bar()`` would raise an ``IndexError`` on the return line of ``foo``,
IPython 8.0 is capable of telling you, where the index error occurs::

    return x[0][i][0]
                ^


Numfocus Small Developer Grant
------------------------------

To prepare for Python 3.10 we have also started working on removing reliance and
any dependency that is not Python 3.10 compatible; that include migrating our
test suite to pytest, and starting to remove nose. This also mean that the
``iptest`` command is now gone, and all testing is via pytest.

This was in bog part thanks the NumFOCUS Small Developer grant, we were able to
allocate 4000 to hire `Nikita Kniazev @Kojoley <https://github.com/Kojoley>`__
who did a fantastic job at updating our code base, migrating to pytest, pushing
our coverage, and fixing a large number of bugs. I highly recommend contacting
them if you need help with C++ and Python projects

You can find all relevant issues and PRs with the SDG 2021 tag:

https://github.com/ipython/ipython/issues?q=label%3A%22Numfocus+SDG+2021%22+

Removing support for Older Python
---------------------------------


We are also removing support for Python up to 3.7 allowing internal code to use more
efficient ``pathlib``, and make better use of type annotations.

IMAGE : Pathlib, pathlib everywhere.

The completer has also seen significant updates and make use of newer Jedi API
offering faster and more reliable tab completion.

For the terminal users this also enable the auto-suggestion feature, described
below, which show "ghost text" ahead of your cursor you can accept without
having to press the tab key or ask the completer to suggest completions.


Autosuggestion is a very useful feature available in `fish <https://fishshell.com/>`__, `zsh <https://en.wikipedia.org/wiki/Z_shell>`__, and `prompt-toolkit <https://python-prompt-toolkit.readthedocs.io/en/master/pages/asking_for_input.html#auto-suggestion>`__.

`Ptpython <https://github.com/prompt-toolkit/ptpython#ptpython>`__ allows users to enable this feature in
`ptpython/config.py <https://github.com/prompt-toolkit/ptpython/blob/master/examples/ptpython_config/config.py#L90>`__.

This feature allows users to accept autosuggestions with ctrl e, ctrl f,
or right arrow as described below.

1. Start ipython

.. image:: ../_images/auto_suggest_prompt_no_text.png

2. Run ``print("hello")``

.. image:: ../_images/auto_suggest_print_hello_suggest.png

3. Press p to see the autosuggestion

.. image:: ../_images/auto_suggest_print_hello_suggest.png

4. Press ctrl f, or ctrl e, or right arrow to accept the suggestion

.. image:: ../_images/auto_suggest_print_hello.png

You can also complete word by word:

1. Run ``def say_hello(): print("hello")``

.. image:: ../_images/auto_suggest_second_prompt.png

2. Press d to see the autosuggestion

.. image:: ../_images/audo_suggest_d_phantom.png

3. Press alt f to accept the first word of the suggestion

.. image:: ../_images/auto_suggest_def_phantom.png

Importantly, this feature does not interfere with tab completion:

1. After running ``def say_hello(): print("hello")``, press d

.. image:: ../_images/audo_suggest_d_phantom.png

2. Press Tab to start tab completion

.. image:: ../_images/auto_suggest_d_completions.png

3A. Press Tab again to select the first option

.. image:: ../_images/auto_suggest_def_completions.png

3B. Press alt f to accept to accept the first word of the suggestion

.. image:: ../_images/auto_suggest_def_phantom.png

3C. Press ctrl f or ctrl e to accept the entire suggestion

.. image:: ../_images/auto_suggest_match_parens.png

To install a version of ipython with autosuggestions enabled, run:

``pip install git+https://github.com/mskar/ipython@auto_suggest``

Currently, autosuggestions are only shown in the emacs or vi insert editing modes:

- The ctrl e, ctrl f, and alt f shortcuts work by default in emacs mode.
- To use these shortcuts in vi insert mode, you will have to create `custom keybindings in your config.py <https://github.com/mskar/setup/commit/2892fcee46f9f80ef7788f0749edc99daccc52f4/>`__.


Show pinfo information in ipdb using "?" and "??"
-------------------------------------------------

In IPDB, it is now possible to show the information about an object using "?"
and "??", in much the same way it can be done when using the IPython prompt::

    ipdb> partial?
    Init signature: partial(self, /, *args, **kwargs)
    Docstring:
    partial(func, *args, **keywords) - new function with partial application
    of the given arguments and keywords.
    File:           ~/.pyenv/versions/3.8.6/lib/python3.8/functools.py
    Type:           type
    Subclasses:

Previously, "pinfo" or "pinfo2" command had to be used for this purpose.


Autoreload 3 feature
====================

Example: When an IPython session is ran with the 'autoreload' extension loaded,
you will now have the option '3' to select which means the following:

    1. replicate all functionality from option 2
    2. autoload all new funcs/classes/enums/globals from the module when they're added
    3. autoload all newly imported funcs/classes/enums/globals from external modules

Try ``%autoreload 3`` in an IPython session after running ``%load_ext autoreload``

For more information please see unit test -
    extensions/tests/test_autoreload.py : 'test_autoload_newly_added_objects'


Miscelanious
------------

Minimum supported


History Range Glob feature
==========================

Previously, when using ``%history``, users could specify either
a range of sessions and lines, for example:

.. code-block:: python

   ~8/1-~6/5   # see history from the first line of 8 sessions ago,
               # to the fifth line of 6 sessions ago.``

Or users could specify a glob pattern:

.. code-block:: python

   -g <pattern>  # glob ALL history for the specified pattern.

However users could *not* specify both.

If a user *did* specify both a range and a glob pattern,
then the glob pattern would be used (globbing *all* history) *and the range would be ignored*.

---

With this enhancement, if a user specifies both a range and a glob pattern, then the glob pattern will be applied to the specified range of history.

Don't start a multi line cell with sunken parenthesis
-----------------------------------------------------

From now on IPython will not ask for the next line of input when given a single
line with more closing than opening brackets. For example, this means that if
you (mis)type ']]' instead of '[]', a ``SyntaxError`` will show up, instead of
the ``...:`` prompt continuation.

IPython shell for ipdb interact
-------------------------------

The ipdb ``interact`` starts an IPython shell instead of Python's built-in ``code.interact()``.

Automatic Vi prompt stripping
=============================

When pasting code into IPython, it will strip the leading prompt characters if
there are any. For example, you can paste the following code into the console -
it will still work, even though each line is prefixed with prompts (`In`,
`Out`)::

    In [1]: 2 * 2 == 4
    Out[1]: True

    In [2]: print("This still works as pasted")


Previously, this was not the case for the Vi-mode prompts::

    In [1]: [ins] In [13]: 2 * 2 == 4
       ...: Out[13]: True
       ...:
      File "<ipython-input-1-727bb88eaf33>", line 1
        [ins] In [13]: 2 * 2 == 4
              ^
    SyntaxError: invalid syntax

This is now fixed, and Vi prompt prefixes - ``[ins]`` and ``[nav]`` -  are
skipped just as the normal ``In`` would be.

IPython shell can be started in the Vi mode using ``ipython
--TerminalInteractiveShell.editing_mode=vi``

Empty History Ranges
====================

A number of magics that take history ranges can now be used with an empty
range. These magics are:

 * ``%save``
 * ``%load``
 * ``%pastebin``
 * ``%pycat``

Using them this way will make them take the history of the current session up
to the point of the magic call (such that the magic itself will not be
included).

Therefore it is now possible to save the whole history to a file using simple
``%save <filename>``, load and edit it using ``%load`` (makes for a nice usage
when followed with :kbd:`F2`), send it to dpaste.org using ``%pastebin``, or
view the whole thing syntax-highlighted with a single ``%pycat``.

Traceback improvements
======================


UPDATE THIS IN INPUT.

Previously, error tracebacks for errors happening in code cells were showing a hash, the one used for compiling the Python AST::

    In [1]: def foo():
    ...:     return 3 / 0
    ...:

    In [2]: foo()
    ---------------------------------------------------------------------------
    ZeroDivisionError                         Traceback (most recent call last)
    <ipython-input-2-c19b6d9633cf> in <module>
    ----> 1 foo()

    <ipython-input-1-1595a74c32d5> in foo()
        1 def foo():
    ----> 2     return 3 / 0
        3

    ZeroDivisionError: division by zero

The error traceback is now correctly formatted, showing the cell number in which the error happened::

    In [1]: def foo():
    ...:     return 3 / 0
    ...:

    In [2]: foo()
    ---------------------------------------------------------------------------
    ZeroDivisionError                         Traceback (most recent call last)
    In [2], in <module>
    ----> 1 foo()

    In [1], in foo()
        1 def foo():
    ----> 2     return 3 / 0

    ZeroDivisionError: division by zero

Remove Deprecated Stuff
=======================


We no longer need to add `extensions` to the PYTHONPATH because that is being
handled by `load_extension`.

We are also removing Cythonmagic, sympyprinting and rmagic as they are now in
other packages and no longer need to be inside IPython.

.. DO NOT EDIT THIS LINE BEFORE RELEASE. FEATURE INSERTION POINT.

As a reminder, IPython master has diverged from the 7.x branch, thus master may
have more feature and API changes.

Backwards incompatible changes
------------------------------

.. DO NOT EDIT THIS LINE BEFORE RELEASE. INCOMPAT INSERTION POINT.