Remove duplicate build preset declarations

[RLovelett]

Python 3's configparser does not parse in the same way that Python 2's did. Specifically, Python 3's does not allow duplicate sections (or in Swift parlance presets).

Python 3 does provide a "strict" property that can be sent to the constructor to return to the behavior of Python 2 (e.g., config = ConfigParser.SafeConfigParser(substitutions, allow_no_value=True, strict=False)). However, this provides it's own set of complications in that the Python 2 version of the constructor does not.

Therefore, instead of having a conditional in the runtime to detect which version of Python and build the correct initializer this patch normalizes the presets configuration file such that there are no more duplicates. This should work in both Python 2 and 3.

Also worth noting: this patch is insufficient by itself to make the build scripts work with Python 3. This patch is written with the "Incremental Development" theory in mind and in preparation for other patches currently in progress, (i.e., #90).

[benlangmuir]

Why did you inline the settings into the presets? For example, you added settings to buildbot,tools=RA,stdlib=DA that looks identical to what's already there because of mixin_buildbot_tools_RA_stdlib_DA.

[RLovelett]

@benlangmuir I guess I don't fully understand the question. So instead I'll explain what I did and then hopefully that makes sense.

If you look at build-presets.ini on master the definition for buildbot,tools=RA,stdlib=DA occurs twice. Once on line 56 and then again on line 179. The Python 3 configparser does not support defining this twice (unless you disable strict mode).

To resolve this I moved the definition made on line 56 down to line 179. It was 99% a cut-and-paste. The only thing that was not cut-and-paste was merging the mixin-preset definition that was made for each individual preset defintion.

I then repeated that same process for preset: buildbot,tools=RA,stdlib=RD and preset: buildbot,tools=RA,stdlib=RDA.

[RLovelett]

@benlangmuir I guess now I see what your saying. The definition of preset: buildbot,tools=RA,stdlib=DA on line 56-68 is exactly the same as the definition of mixin_buildbot_tools_RA_stdlib_DA on line 164-176.

So why not just delete the definition of preset: buildbot,tools=RA,stdlib=DA on line 56-68? Frankly I hadn't noticed it until you asked this question.

That now seems like a better strategy with less churn. I'll update accordingly.

[benlangmuir]

EDIT: didn't see your second comment, which is exactly what I was trying to say here 😺
Okay, that's what I thought happened. My point is that we don't need to merge the first definition into the second one, we can just delete the first definition. The two definitions were already equivalent because the first instance of buildbot,tools=RA,stdlib=DA is identical to mixin_buildbot_tools_RA_stdlib_DA which is used by buildbot,tools=RA,stdlib=DA. Does that make sense?

[RLovelett]

Yeah it does. We are on the same page now. I'll update that.

[RLovelett]

I've rebased this on the latest master (ab29adf) and have incorporated @benlangmuir's suggestion.

[gribozavr]

@RLovelett Did you test any of the affected presets?

[RLovelett]

I've run a build with swift/utils/build-script --preset=buildbot_linux_1510 and it was able to configure and begin running successfully.

EDIT:
I guess I should point out that it has yet to fully compile. However, it got passed the initial build config parsing part and actually started compiling. I just am having a problem where the linker is not finding -lpthread -ldl but I don't think that is related to this patch because I get it with-or-without this patch being applied.

[gribozavr]

This LGTM.