Updating contributing doc to add more detail on how to start

CONTRIBUTING.rst

@@ -124,15 +124,51 @@ See the relevant sections above on how to do this.
 Setting up the environment
 ^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-Follow the steps in the :ref:`installation_instructions` > "From Source" section
-to set up your environment, install the required development dependencies, and
-run the tests.
+To contribute, you will first have to run through some steps:
+
+- Set up your environment by forking the repository (`Github doc on
+  forking and
+  cloning <https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/working-with-forks/fork-a-repo>`__).
+- Create and activate a new virtual environment:
+
+  - With `venv <https://docs.python.org/3/library/venv.html>`__, create
+    the env with ``python -m venv env_skrub`` and then activate it with
+    ``source env_skrub/bin/activate``.
+  - With
+    `conda <https://docs.conda.io/projects/conda/en/latest/user-guide/tasks/manage-environments.html>`__,
+    create the env with ``conda new -n env_skrub`` and activate it with
+    ``conda activate env_skrub``.
+  - While at the root of your local copy of skrub and within the new
+    env, install the required development dependencies by running
+    ``pip install --editable ".[dev, lint, test, doc]"``.
+
+- Run ``pre-commit install`` to activate some checks that will run every
+  time you do a ``git commit`` (mostly, formatting checks).
+
+If you want to make sure that everything runs properly, you can run all
+the tests with the command ``pytest -s skrub/tests``; note that this may
+take a long time. Some tests may raise warnings such as:
 
-When starting to work on a new issue, it's recommended to create a new branch:
+.. code:: sh
+  UserWarning: Only pandas and polars DataFrames are supported, but input is a Numpy array. Please convert Numpy arrays to DataFrames before passing them to skrub transformers. Converting to pandas DataFrame with columns ['0', '1', …].
+    warnings.warn(
+
+This is expected, and you may proceed with the next steps without worrying about them. However, no tests should fail at this point: if they do fail, then let us know.
+
+Now that the development environment is ready, you may start working on
+the new issue by creating a new branch:
+
+.. code:: sh
 
-.. code:: console
+   git checkout -b my-branch-name-eg-fix-issue-123
+   # make some changes
+   git add ./the/file-i-changed
+   git commit -m "my message"
+   git push --set-upstream origin my-branch-name-eg-fix-issue-123
 
-   git switch -c branch_name
+At this point, if you visit again the `pull requests
+page <https://github.com/skrub-data/skrub/pulls>`__ github should show a
+banner asking if you want to open a pull request from your new branch.
 
 
 .. _implementation guidelines:
@@ -183,7 +219,8 @@ Additionally, you might have updated the internal dataframe API in
 ``skrub/_dataframe/tests/test_common.py`` to add a test for the
 ``amazing_function``.
 
-Run each updated test file using ``pytest``:
+Run each updated test file using ``pytest``
+([pytest docs](https://docs.pytest.org/en/stable/)):
 
 .. code:: sh
 
@@ -193,10 +230,20 @@ Run each updated test file using ``pytest``:
 
 The ``-vsl`` flag provides more information when running the tests.
 
+It is also possible to run a specific test, or set of tests using the
+commands ``pytest the_file.py::the_test``, or
+``pytest the_file.py -k 'test_name_pattern'``. This is helpful to avoid
+having to run all the tests.
+
+If you work on Windows, you might have some issues with the working
+directory if you use ``pytest``, while ``python -m pytest ...`` should
+be more robust.
+
 Once you are satisfied with your changes, you can run all the tests to make sure
 that your change did not break code elsewhere:
 
 .. code:: sh
+
     pytest -s skrub/tests
 
 Finally, sync your changes with the remote repository and wait for CI to run.
@@ -229,6 +276,21 @@ the docstrings. Check for possible problems by running
 
    pytest skrub/path/to/file
 
+
+Formatting and pre-commit checks
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Formatting the code well helps with code development and maintenance,
+which is skrub requires that all commits follow a specific set of
+formatting rules to ensure code quality.
+
+Luckily, these checks are performed automatically by the ``pre-commit``
+tool (`pre-commit docs <https://pre-commit.com>`__) before any commit
+can be pushed. Something worth noting is that if the ``pre-commit``
+hooks format some files, the commit will be canceled: you will have to
+stage the changes made by ``pre-commit`` and commit again.
+
+
 Submitting your code
 ^^^^^^^^^^^^^^^^^^^^
 
@@ -237,17 +299,10 @@ a PR by clicking the "Compare & pull request" button on GitHub,
 targeting the skrub repository.
 
 
-Integration
-^^^^^^^^^^^
-
-Community consensus is key in the integration process. Expect a minimum
-of 1 to 3 reviews depending on the size of the change before we consider
-merging the PR.
-
-Please be mindful that maintainers are volunteers, so review times may vary.
-
 Continuous Integration (CI)
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~
+After creating your PR, CI tools will run proceed to run all the tests on all
+configurations supported by skrub.
 
 - **Github Actions**:
   Used for testing skrub across various platforms (Linux, macOS, Windows)
@@ -273,18 +328,32 @@ actions are taken.
 Note that by default the documentation is built, but only the examples that are
 directly modified by the pull request are executed.
 
-- If the remote repository was changed, you might need to run
-  ``pre-commit run --all-files`` to make sure that the formatting is
-  correct.
-- If a specific test environment fails, it is possible to run the tests
-  in the environment that is failing by using pixi. For example if the
-  env is ``ci-py309-min-optional-deps``, it is possible to replicate it
-  using the following command:
+CI is testing all possible configurations supported by skrub, so tests may fail
+with configurations different from what you are developing with. If this is the
+case,  it is possible to run the tests in the environment that is failing by
+using pixi. For example if the env is ``ci-py309-min-optional-deps``, it is
+possible to replicate it using the following command:
 
 .. code:: sh
 
    pixi run -e ci-py309-min-optional-deps  pytest skrub/tests/path/to/test
 
+This command downloads the specific environment on the machine, so you can test
+it locally and apply fixes, or have a clearer idea of where the code is failing
+to discuss with the maintainers.
+
+Finally, if the remote repository was changed, you might need to run
+  ``pre-commit run --all-files`` to make sure that the formatting is
+  correct.
+
+Integration
+^^^^^^^^^^^
+
+Community consensus is key in the integration process. Expect a minimum
+of 1 to 3 reviews depending on the size of the change before we consider
+merging the PR.
+
+Please be mindful that maintainers are volunteers, so review times may vary.
 
 
 Building the documentation

README.rst

@@ -32,7 +32,14 @@ The goal of skrub is to bridge the gap between tabular data sources and machine-
 
 skrub provides high-level tools for joining dataframes (``Joiner``, ``AggJoiner``, ...),
 encoding columns (``MinHashEncoder``, ``ToCategorical``, ...), building a pipeline
-(``TableVectorizer``, ``tabular_learner``, ...), and more.
+(``TableVectorizer``, ``tabular_learner``, ...), and explore interactively your data (``TableReport``).
+
+.. figure::
+   https://github.com/rcap107/skrub-datasets/blob/master/data/output.gif?raw=true
+   :alt: An animation showing how TableReport works
+
+   An animation showing how TableReport works
+
 
 >>> from skrub.datasets import fetch_employee_salaries
 >>> dataset = fetch_employee_salaries()
@@ -69,5 +76,8 @@ The best way to support the development of skrub is to spread the word!
 Also, if you already are a skrub user, we would love to hear about your use cases and challenges in the `Discussions <https://github.com/skrub-data/skrub/discussions>`_ section.
 
 To report a bug or suggest enhancements, please
-`open an issue <https://docs.github.com/en/issues/tracking-your-work-with-issues/creating-an-issue>`_ and/or
-`submit a pull request <https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/proposing-changes-to-your-work-with-pull-requests/creating-a-pull-request>`_.
+`open an issue <https://docs.github.com/en/issues/tracking-your-work-with-issues/creating-an-issue>`_.
+
+If you want to contribute directly to the library, then check the
+`how to contribute <https://skrub-data.org/stable/CONTRIBUTING.html>`_ page on
+the website for more information.