Add deprecation note to pyflyte serialize (#2716)

Signed-off-by: Yee Hing Tong <[email protected]>

docs/source/design/clis.rst

@@ -99,3 +99,23 @@ Both the commands have their own place in a production Flyte setting.
 .. note ::
 
    Neither ``pyflyte register`` nor ``pyflyte run`` commands work on Python namespace packages since both the tools traverse the filesystem to find the first folder that doesn't have an __init__.py file, which is interpreted as the root of the project. Both the commands use this root as the basis to name the Flyte entities.
+
+
+How to move away from the ``pyflyte serialize`` command?
+========================================================
+
+The ``serialize`` command is deprecated around the end of Q3 2024. Users should move to the ``package`` command instead as the two commands provide nearly identical functionality.
+
+Migrate
+-------
+To use the ``package`` command, make the following changes:
+* The ``--local-source-root`` option should be changed to ``--source``
+* If the already ``--in-container-virtualenv-root`` option was specified, then move to the ``--python-interpreter`` option in ``package``. The default Python interpreter for serialize was based on this deprecated flag, and if not specified, ``sys.executable``. The default for ``package`` is ``/opt/venv/bin/python3``. If that is not where the Python interpreter is located in the task container, then you'll need to now specify ``--python-interpreter``.  Note that this was only used for Spark tasks.
+* The ``--in-container-config-path`` option should be removed as this was not actually being used by the ``serialize`` command.
+
+
+Functional Changes
+------------------
+Beyond the options, the ``package`` command differs in that
+* Whether or not to use fast register should be specified by the ``--copy auto`` or ``--copy all`` flags, rather than ``fast`` being a subcommand.
+* The serialized file output by default is in a .tgz file, rather than being separate files. This means that any subsequent ``flytectl register`` command will need to be updated with the ``--archive`` flag.

flytekit/clis/sdk_in_container/serialize.py

@@ -3,6 +3,7 @@
 import typing
 from enum import Enum
 
+import rich
 import rich_click as click
 
 from flytekit.clis.sdk_in_container import constants
@@ -136,6 +137,12 @@ def serialize(
     ctx.obj[CTX_IMAGE] = image_config
     ctx.obj[CTX_LOCAL_SRC_ROOT] = local_source_root
     ctx.obj[CTX_ENV] = env
+    rich.print(
+        "[bold bright_green on black][Deprecation notice]\nThis 'serialize' command is being deprecated,"
+        " please move to using 'package' instead."
+        " See [link=https://docs.flyte.org/en/latest/api/flytekit/design/clis.html#pyflyte]docs[/link]"
+        " for more information.[/]\n"
+    )
     click.echo(f"Serializing Flyte elements with image {image_config}")
 
     if in_container_virtualenv_root: