mamba/docs/source/developer_zone/changes-2.0.rst

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Mamba 2.0 Changes
=================
.. ...................... ..
.. THIS IS STILL A DRAFT ..
.. ...................... ..
.. TODO high-level summary of new features:
.. - OCI registries
.. - Mirrors
.. - Own implementation repodata.json
Command Line Executables
------------------------
Mamba (executable)
******************
``mamba``, previously a Python executable mixing ``libmambapy``, ``conda``, and code to bridge both
project is being replace by a fully C++ executable based on ``libmamba`` solely.
It now presents the same user interface and experience as ``micromamba``.
.. warning::
The previous code being a highly complex project with few of its original developers still
active, it is hard to make an exhaustive list of all changes.
Please help us by reporting changes missing changes.
Micromamba
**********
Micromamba receives all new features and its CLI remains mostly unchanged.
Breaking changes include:
- ``micromamba shell init`` root prefix parameter ``--prefix`` (``-p``) was renamed
``--root-prefix`` (``-r``).
Both options were supported in version ``1.5``.
- A new config ``order_solver_request`` (default true) can be used to order the dependencies passed
to the solver, getting order independent solutions.
- Support for complex match specs such as ``pkg[md5=0000000000000]`` and ``pkg[build='^\d*$']``.
.. TODO OCI and mirrors
Libraries
---------
Mamba (Python package)
**********************
In version 2.0, all tools are fully written in C++.
All code previously available in Python through ``import mamba`` has been removed.
Libmambapy (Python bindings)
****************************
The Python bindings to the C++ ``libmamba`` library remain available through ``import libmambapy``.
They are now considered the first class citizen to using Mamba in Python.
Changes include:
- The global ``Context``, previously available through ``Context()``, must now be accessed through
``Context.instance()``.
What's more, it is required to be passed explicitly in a few more functions.
Future version of ``libmambapy`` will continue in this direction until there are no global context.
In version 2, ``Context()`` will throw an exception to allow catching errors more smoothly.
- ``ChannelContext`` is no longer an implicit global variable.
It must be constructed with one of ``ChannelContext.make_simple`` or
``ChannelContext.make_conda_compatible`` (with ``Context.instance`` as argument in most cases)
and passed explicitly to a few functions.
- A new ``Context`` independent submodule ``libmambapy.specs`` has been introduced with:
- The redesign of the ``Channel`` and a new ``UnresolvedChannel`` used to describe unresolved
channel strings.
A featureful ``libmambapy.specs.CondaURL`` is used to describe channel URLs.
- The redesign of ``MatchSpec``.
The module also includes a platform enumeration, an implementation of ordered ``Version``,
and a ``VersionSpec`` to match versions.
- ``PackageInfo`` has been moved to this submodule.
Some attributes have been given a more explicit name ``fn`` > ``filename``,
``url`` > ``package_url``.
- A new ``Context`` independent submodule ``libmambapy.solver`` has been introduced with the
changes below.
A usage documentation page is available at :ref:`mamba_usage_solver`.
- The redesign of the ``Pool``, which is now available as ``libmambapy.solver.libsolv.Database``.
The new interfaces make it easier to create repositories without using other ``libmambapy``
objects.
- ``Repo`` has been redesigned into a lightweight ``RepoInfo`` and moved to
``libmambapy.solver.libsolv``.
The creation and modification of repos happen through the ``Database``, with methods such as
``Database.add_repo_from_repodata_json`` and ``Database.add_repo_from_packages``, but also
high-level free functions such as ``load_subdir_in_database`` and
``load_installed_packages_in_database``.
- The ``Solver`` has been moved to ``libmambapy.solver.libsolv.Solver``.
- All jobs, pins, and flags must be passed as a single ``libmambapy.solver.Request``.
- The outcome of solving the request is either a ``libmambapy.solver.Solution`` or a
``libmambapy.solver.libsolv.Unsolvable`` state from which rich error messages can be
extracted.
For many changes, an exception throwing placeholders has been kept to advise developers on the new
direction to take.
Libmamba (C++)
**************
The C++ library ``libmamba`` has received significant changes.
Due to the low usage of the C++ interface, all changes are not listed here.
The main changes are:
- Refactoring and testing of a large number of utilities into a ``util::`` namespace.
- Creation of ``specs::`` including the items below.
A usage documentation (in Python) is available at :ref:`mamba_usage_specs`.
- Implementations of ``Version`` and ``VersionSpec`` for matching versions,
- A refactoring of a purely functional ``Channel`` class,
- Implementation of a ``UnresolvedChannel`` to describe unresolved ``Channels``,
- A refactored and complete implementation of ``MatchSpec`` using the components above.
- A cleanup of ``ChannelContext`` to be a light proxy and parameter holder wrapping the
``specs::Channel``.
- A new ``repodata.json`` parser using `simdjson <https://simdjson.org/>`_.
- The ``MPool``, ``MRepo`` and ``MSolver`` API has been completely redesigned into a ``solver``
subnamespace and works independently of the ``Context``.
The ``solver::libsolv`` sub-namespace has also been added for full isolation of libsolv, and a
solver API without ``Context``.
The ``solver`` API redesign includes the items below.
A usage documentation (in Python) is available at :ref:`mamba_usage_solver`.
- A refactoring of the ``MPool`` as a ``DataBase``, fully isolates libsolv, and simplifies
repository creation.
- A refactoring and thinning of ``MRepo`` as a new ``RepoInfo``.
- A solver ``Request`` with all requirements to solve is the new way to specify jobs.
- A refactoring of ``Solver``.
- A solver outcome as either a ``Solution`` or an ``UnSolvable`` state.
- Plug of the Mamba's ``MatchSpec`` implementation in the ``Solver``, enabling the solving of all
types of previously unsupported MatchSpecs.
- Improved downloaders.
.. TODO OCI registry
.. TODO Mirrors