[lldb-dev] Deprecating Python2 and adding type-annotations to the python API

[Pavel Labath via lldb-dev]

On 04/08/2020 02:37, Jonas Devlieghere via lldb-dev wrote:
> Hi Nathan,
> 
> Thanks for bringing this up. I've been expecting this question for a
> while now. 
> 
> Python 2 is end-of-life and we should move to Python 3. I'm pretty sure
> nobody here disagrees with that. Unfortunately though, we still have
> consumers, both internally and externally, that still rely on it. We're
> actively making an effort to change that, but we're not quite there yet. 
> 
> That said, I think we should continue moving in that direction. In line
> with the rest of LLVM moving to Python 3 by the end of the year, we've
> already made it the default. All our bots on GreenDragon are also
> building against Python 3.
> 
> As a first step, for the next release, I propose we remove the fallback
> to Python 2 and make it the only supported configuration. At the same
> time we can convert any scripts and tools (I'm thinking of the lit
> configurations, the lldb-dotest and lldb-repro wrappers, etc) to be
> Python 3 only. During this time however, we'd ask that the bindings and
> the test suite remain compatible with Python 2. Given that Python 3 is
> the only supported configuration for developers, we'd take on the burden
> of maintaining Python 2 compatibility in the test suite and correcting
> (accidental) incompatibilities.
> 
> When the 12.0 release is cut, we can reconsider the situation. If we're
> still not ready by then to drop Python 2 support, I  propose another
> intermediate step where we remove Python 2 support from the upstream
> repository, but ask the community to not actively modernize the test
> suite and the bindings. In this situation we'd be dealing with the merge
> conflicts in our downstream fork and this would avoid an endless number
> of conflicts in the test suite. 
> 
> Finally, presumably after the 13.0 release, we'd drop that last
> requirement. 
> 
> Please let me know if you think that sounds like a reasonable timeline.
> 
> Thanks,
> Jonas
> 



This sounds like a good plan to me. If lldb is supposed to remain
buildable with python2, then I also don't see a problem with keeping the
cmake bits which enable that. We could make it harder to build with
python2 accidentally by requiring the user to set a variable similar to
the LLVM_TEMPORARILY_ALLOW_OLD_TOOLCHAIN thingy.

pl