[Scons-users] Compact notation

[Andrew C. Morrow]

Hi -

Great suggestion! I just tried it, and it definitely works. Supporting None
would be nice too, as it seems a little clearer, but I can work with [].

OK, so that leaves question 2. Any ideas on a way to do accumulative
environment modifications inline when declaring a target?

Thanks,
Andrew

On Sun, Dec 11, 2016 at 11:27 AM, Brian Cody <brian.j.cody at gmail.com> wrote:

> Hey Andrew,
>
> For your first issue, does this work:
>
> env.Library(
>     target="foo",
>     source=[
>         'source1.cpp',
>         'source2.cpp',
>         'source_windows.cpp' if windows else [],
>     ],
>     LIBS=[
>         'lib1',
>         'lib2',
>         'lib_windows' if windows else [],
>     ]
> )
>
> I think it will automatically flatten the lists internally.
>
> On Sun, Dec 11, 2016 at 10:55 AM, Andrew C. Morrow <
> andrew.c.morrow at gmail.com> wrote:
>
>>
>> Over the past few years, I've encountered a few things that seem to lead
>> to more-verbose-than-needed python code when writing SConscripts, leading
>> to a less declarative feel. I've recently been thinking about how I would
>> want to write these things better. Perhaps others have encountered these
>> same issues and have found solutions?
>>
>> 1) Conditionally including a file or library:
>>
>> If I have a library that may or may not include a particular file (say,
>> based on if the target platform is windows), I generally need to pull the
>> list of sources out, and then conditionally append:
>>
>> fooSources=[
>>     'source1.cpp',
>>     'source2.cpp',
>> ]
>>
>> fooLibs=[
>>     'lib1',
>>     'lib2,
>> ]
>>
>> if windows:
>>    fooSources.append('source_windows.cpp')
>>    fooLibs.append('lib_windows')
>>
>> env.Library(
>>     target='foo',
>>     source=fooSources
>>     LIBS=fooLibs
>> )
>>
>> It would be nicer to write:
>>
>> env.Library(
>>     target="foo",
>>     source=[
>>         'source1.cpp',
>>         'source2.cpp',
>>         'source_windows.cpp' if windows else None,
>>     ],
>>     LIBS=[
>>         'lib1',
>>         'lib2',
>>         'lib_windows' if windows else None,
>>     ]
>> )
>>
>> But SCons seems to reject this:
>>
>> AttributeError: 'NoneType' object has no attribute 'name':
>>
>> Would it be a reasonable enhancement request that the various built-in
>> builders filter incoming lists for None? Is there another way to achieve
>> this? I could obviously attach filter each expression for None at the point
>> of its declaration, but that seems verbose.
>>
>> It doesn't come up often, but it would be nice.
>>
>>
>> 2) Inline manipulation of Environment variables.
>>
>> I can easily override an Env var when declaring a target:
>>
>> // Happens far away
>> env.Append(CPPDEFINES="whatever")
>>
>> env.Library(
>>     target="foo",
>>     source=...
>>     CPPDEFINES=["applies"]
>> )
>>
>> This will build with -Dapplies, overriding "whatever" in CPPDEFINES for
>> the sources in this target. But what if I want to Append or Prepend
>> (Unique), instead of override? There doesn't seem to be a compact syntax
>> for that. I need to write:
>>
>> // Happens far away
>> env.Append(CPPDEFINES=["whatever"])
>>
>> env = env.Clone()
>> env.AppendUnique(CPPDEFINES=["applies"])
>> env.Library(
>>     target="foo",
>>     source=...
>> )
>>
>> Now I get both -Dwhatever and -Dapplies for the sources.
>>
>> But what I'd really like to write is:
>>
>>
>> // Happens far away
>> env.Append(CPPDEFINES=["whatever"])
>>
>> env.Library(
>>     target="foo",
>>     source=...
>>     CPPDEFINES=UniqueAppender(["applies"]),
>> )
>>
>> Where UniqueAppender is a mutator that causes the effects of
>> env.AppendUnique(arg) to be applied to the local Environment for the target.
>>
>> Is there any existing mechanism to achieve this? If not, is it possible?
>> Reasonable? Other suggestions for how to do this?
>>
>> Combining the two techniques:
>>
>> Old:
>>
>> fooSources=[
>>     'source1.cpp',
>>     'source2.cpp',
>> ]
>>
>> fooLibs=[
>>     'lib1',
>>     'lib2,
>> ]
>>
>> if windows:
>>    fooSources.append('source_windows.cpp')
>>    fooLibs.append('lib_windows')
>>
>> env = env.Clone()
>> env.AppendUnique(CPPDEFINES=["applies"])
>> env.Library(
>>     target='foo',
>>     source=fooSources
>>     LIBS=fooLibs
>> )
>>
>> New (and making the 'applies' conditional as well, just for fun):
>>
>>
>> env.Library(
>>     target="foo",
>>     source=[
>>         'source1.cpp',
>>         'source2.cpp',
>>         'source_windows.cpp' if windows else None,
>>     ],
>>     CPPDEFINES=UniqueAppender([
>>         "applies" if windows else None,
>>     ]),
>>     LIBS=[
>>         'lib1',
>>         'lib2',
>>         'lib_windows' if windows else None,
>>     ]
>> )
>>
>> I think these two features would go a long way towards making complex
>> SConscripts more declarative.
>>
>> Thoughts? Suggestions? Ways I can do this now with SCons that I'm missing?
>>
>> Thanks,
>> Andrew
>>
>>
>>
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>>
>>
>
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