[Scons-users] Finding targets which depend on a source file

[Bill Deegan]

Stefan,

scons --tree=prune should yield the info you're asking about.
If you want something different, feel free to implement it, create some
tests for it, and submit a pull request.

-Bill

On Thu, Nov 19, 2015 at 1:07 AM, Stefan Ross <stefan at electricimp.com> wrote:

> I also have found myself wanting this feature.  Not because Scons is doing
> the wrong thing, but because it's helpful when building SConscript files to
> have this information.  For example, I recently did a big refactoring on a
> codebase where I wasn't that familiar with the whole codebase, including
> its dependencies.  So it's possible that I refactored some of the tools out
> such that nothing depended on them, but there's no easy way to find this
> out.  I could delete the tool, do a clean, and rebuild, but that's a slow
> cycle.  Having Scons report such dependencies would be helpful.
>
> I had other examples where I had output files with the same name in
> different directories (I was moving things about).  Sometimes I got
> confused about which version of the file was being referenced.  I know
> there are other ways of finding these, but a single command to check if a
> particular file had any other files depending on it would have been helpful.
>
> Thanks
>
> Stefan
>
> On Wed, Nov 18, 2015 at 11:50 PM, Bill Deegan <bill at baddogconsulting.com>
> wrote:
>
>> scons will do what you are asking without you having to explicitly list
>> them on  the command line.
>> If it's doing the wrong thing, file a bug.
>>
>> I can't fathom a reason to do what you are asking to do.
>> Can you supply a reason to your madness so that perhaps we can propose a
>> way which make sense for scons?
>>
>> You can use the --tree=prune output as well to see what depends on what.
>>
>> -Bill
>>
>> On Wed, Nov 18, 2015 at 3:47 PM, William Blevins <wblevins001 at gmail.com>
>> wrote:
>>
>>>
>>>
>>> On Wed, Nov 18, 2015 at 11:16 PM, Abhishek Rai <abhishekrai at gmail.com>
>>> wrote:
>>>
>>>> Thanks for the prompt response William.
>>>>
>>>> On Wed, Nov 18, 2015 at 3:06 PM, William Blevins <wblevins001 at gmail.com>
>>>> wrote:
>>>> >
>>>> > SCons already only builds targets that are not up-to-date, so what is
>>>> the point of this script per say? I assume that you are always starting
>>>> from a fresh repository clone of some kind?
>>>>
>>>> Yes.  In our git repository, we pull code from the origin several times
>>>> every day.  After each pull, as far as scons goes, several build targets
>>>> become out of date, causing it to rebuild them when we try to build all
>>>> targets.  In our environment, it's safe to assume that code pulled from
>>>> origin passes all builds and tests, therefore rebuilding locally is an
>>>> overkill.
>>>>
>>>> >
>>>> > The SCons paradigm generally maps Targets to Dependencies (Sources),
>>>> so you would need to work backwards.  You might be able to get this
>>>> information from "scons --dry-run --tree=<option>" with a clever parser,
>>>> but this will require that SCons scan all the files even though it might
>>>> not build targets.
>>>>
>>>> The --dry-run option unfortunately suffers from the similar limitation
>>>> - it finds that most targets are out of date, including those unaffected by
>>>> local changes.
>>>>
>>>
>>> dry-run doesn't execute the build statements, so my point here was to
>>> get the dependency tree output without compiling.  You can then find
>>> entries in the tree that map to local changes (files shown by git status,
>>> etc); this of course can give you the final target if you follow the tree
>>> to the root. You will need a parser for the tree output which shouldn't be
>>> too complicated, but it might not be efficient either.
>>>
>>>
>>>>
>>>> >
>>>> > I am not sure if there is a better way.
>>>> >
>>>> > V/R,
>>>> > William
>>>>
>>>> Thanks!
>>>> Abhishek
>>>>
>>>> >
>>>> > On Wed, Nov 18, 2015 at 10:53 PM, Abhishek Rai <abhishekrai at gmail.com>
>>>> wrote:
>>>> >>
>>>> >> Hello,
>>>> >>
>>>> >> Is there any way in scons to list all targets which depend on a
>>>> given source file?
>>>> >>
>>>> >> In the code base that I'm working on, we have a "pre-commit" script
>>>> which verifies whether the changes in the commit break any targets.
>>>> Currently, this script tries to build all targets.  Of course, some targets
>>>> may not need rebuilding if the corresponding source files haven't changed
>>>> since the previous build.  But given the dynamic nature of the code base,
>>>> each run of the pre-commit script ends up building nearly all targets even
>>>> if that commit affects only a small number of them.
>>>> >>
>>>> >> Having the ability to list all targets derived from a given source
>>>> file will give us the ability to list out these targets first, and then
>>>> only build those targets as part of the pre-commit workflow.
>>>> >>
>>>> >> Thanks!
>>>> >> Abhishek
>>>> >>
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>>>> >
>>>> >
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>>>
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