Re: [PATCH 1/1] edksetup.sh: rework python executable scanning

["Laszlo Ersek" <lersek@redhat.com>]

On 07/17/19 05:23, Gao, Liming wrote:
> Leif:
>   I agree to discuss the behavior first, then review the code logic in detail. I add my comments below. 
> 
>> -----Original Message-----
>> From: Leif Lindholm [mailto:leif.lindholm@linaro.org]
>> Sent: Wednesday, July 17, 2019 6:05 AM
>> To: Laszlo Ersek <lersek@redhat.com>
>> Cc: devel@edk2.groups.io; Rebecca Cran <rebecca@bsdio.com>; Feng, Bob C <bob.c.feng@intel.com>; Gao, Liming
>> <liming.gao@intel.com>; Kinney, Michael D <michael.d.kinney@intel.com>; afish@apple.com
>> Subject: Re: [PATCH 1/1] edksetup.sh: rework python executable scanning

>> - What does PYTHON3_ENABLE mean? Is it for probing only, or are we
>>   setting it for later use by BaseTools?
> 
> PYTHON3_EANBLE is to decide python3 enable or not. It has high priority.
> Once it is set, PYTHON_COMMAND will be ignored.
>   If it is set to TRUE, edksetup.sh will find Python3 in the system, set PYTHON_COMMAND env. 
>   If it is set to other value, edksetup.sh will find Python3 in the system, set PYTHON_COMMAND env.
> If PYTHON3_EANBLE is not set, PYTHON_COMMAND will be used if PYTHON_COMMAND is set. 
> If PYTHON3_EANBLE is not set, and PYTHON_COMMAND is not set, the default behavior will set PYTHON3_EANBLE to TRUE.

I find this confusing. Basically, PYTHON3_EANBLE says, "ignore
PYTHON_COMMAND, just go for the highest python3 version".

But that is the exact same behavior as if the user didn't set *either*
PYTHON3_EANBLE *or* PYTHON_COMMAND. So why do we have two configurations
for the exact same behavior?

Namely (to repeat):

(1) PYTHON3_EANBLE is set to a non-null string: PYTHON_COMMAND is
ignored, and we pick the highest minor version of python3.

(2) PYTHON3_EANBLE is unset, and PYTHON_COMMAND is unset: we pick the
highest minor version of python3.

Those configurations -- evoking identical behavior -- could be collapsed
into one configuration, namely, if we simply eliminated PYTHON3_EANBLE,
and relied on PYTHON_COMMAND only. Here's how:

* PYTHON_COMMAND is unset: pick the highest minor version of python3.

Thanks
Laszlo