[Buildroot] [RFC] python: select vs depends on

[Yann E. MORIN]

On 2013-12-24 18:14 +0100, Thomas De Schampheleire spake thusly:
> Currently, we have a dual strategy with respect to packages that have
> optional Python support: alsa-lib uses 'depends on python' for its
> 'python support' option, while ola uses 'select python' for its
> 'python bindings'.
[--SNIP--]
> - python modules (typically named python-foo): here the current
> strategy is to use 'depends on', and this is followed by all such
> packages. For me, this is perfectly sane, and is (IMO) not open for
> discussion.
> Note: in fact, all these modules are in one 'if python' block in
> package/Config.in, and I have prepared a patch to remove the redundant
> 'depends on'.
> 
> - for 'normal' packages that need python for there normal behavior, we
> typically use 'select python'. In this case, the user may not be aware
> of the python dependency, and requiring him/her to first enable python
> is not logical. I think this reasoning is sane too.
> 
> - for 'normal' packages that do not require python, but have optional
> python support (as is the case for ola and alsa-lib), I have no strong
> preference. Whichever is preferred by the community is ok with me, as
> long as we keep one guideline for this case.

Or what about just removing the 'depends on' or 'select' for packages
sub-options, and just add the dependencies and options in the .mk files,
such as:

---8<--- alsa-lib.mk ---8<---
ifeq ($(or $(BR2_PACKAGE_PYTHON),$(BR2_PACKAGE_PYTHON3)),y)
ALSA_LIB_CONF_OPT += \
        --with-pythonlibs=-lpython$(PYTHON_VERSION_MAJOR) \
        --with-pythonincludes=$(STAGING_DIR)/usr/include/python$(PYTHON_VERSION_MAJOR)
ALSA_LIB_CFLAGS+=-I$(STAGING_DIR)/usr/include/python$(PYTHON_VERSION_MAJOR)
ALSA_LIB_DEPENDENCIES = python
else
ALSA_LIB_CONF_OPT += --disable-python
endif
---8<--- alsa-lib.mk ---8<---

And so on for other packages...

We already ave this behaviour in other packages:
  - bind adds features if openssl or libxml2 are selected
  - libvncserver, with libgcrypt, libjpeg, or openssl
  - libpcap, with libusb or libnl
  - and so on. countless times...

Regards,
Yann E. MORIN.

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