Usability: Improve "tools/mpy_cross_all" to invoke the "mpy-cross" program coming from the mpy_cross distribution

[amotl]

Dear @pfalcon, @dpgeorge, @stinos, @dhylands and all maintainers of good faith in MicroPython tooling,

first things first: Thank you so much for your amazing work on MicroPython and its ecosystem - you know who you are.

Introduction

Coming from https://github.com/micropython/micropython/issues/4955 and building upon https://github.com/micropython/micropython/issues/3040 and https://github.com/micropython/micropython/issues/3057, we enabled tools/mpy_cross_all.py to invoke the mpy-cross program through the fine mpy-cross distribution package.

Setup

The operator will be able to decide to selectively install specific versions of mpy-cross like

source .venv2/bin/activate
pip install mpy-cross=1.9.4

into the Python environment running on her workstation.

Usage

Description

When running it from a Python environment where the mpy_cross modules is installed, mpy_cross_all.py will attempt to invoke mpy-cross from the mpy_cross distribution.

Otherwise, it will go down the established route of invoking mpy-cross directly, essentially expecting it to reside somewhere on $PATH.

Synopsis

source .venv2/bin/activate
time python tools/mpy_cross_all.py --out dist-packages-mpy dist-packages

real    0m0.439s
user    0m0.152s
sys 0m0.247s

We hope you like this.

With kind regards, Andreas.

[pfalcon]

Thanks for your patch.

Pycopy is a principled project, with "right vs wrong" principles clearly (hopefully) described at https://github.com/pfalcon/pycopy#the-pycopy-zen .

This patch contradicts those principles on a few accounts:

• It makes mpy_cross_all.py more complex, without clearly describing the need for this, whereas Pycopy's aim is simplicity.
• The patch itself is complex, clearly not optimized for minimal impact, ease of review or maintenance.
• Pycopy's goal is to be self-hosted and full-stack language, to be able to run its own support tools. This patch represents retrograde action of adding dependency on outside project(s), whereas the goal is to get rid of such dependencies in tools which still have them.

Thus, it's not a good fit for Pycopy, sorry.