[Scons-users] Value/Alias Nodes default to up-to-date

[Brad Kraemer]

* Fixed subject line (the original line from the mailer daemon added 
JUNK, as this one doesn't allow unconfirmed posters, i.e. I should have 
waited for the mailing-list confirmation before sending the first e-mail 
off)


Currently, just experimenting with some SCons features. At this time I 
was creating an Alias() because I wanted the Alias() object (which is 
namespaced outside the regular FS namespace), allowing me to make 
Action()'s with dependency orderings. While not having these actions 
kicked off by running something like '$ scons /' (which something like 
Command() would).


I realize this is outside the intended use of these functions. However, 
the doc's don't forbid it so it's clean in my eyes.

The Command() part is just for something to depend on (can replace it 
with Program() or any other builder, my issue is with the Alias() lines).


Your reasoning makes sense, however, if my Alias is never out of date 
(i.e. on creation it's meant to be considered already built), why can I 
run AlwaysBuild() and thus force it to build (is this the equivalent of 
rebuilding something already up-to-date)?

Just looking at the sources, it seems these Node's are meant to be built 
at least once (however, Value() in particular does seem to have a 
parameter to be considered built on creation). Or am I off base with this?


On 2022-01-02 5:30 p.m., Bill Deegan wrote:
> Maybe you explain what you're trying to do, rather than how you're 
> currently trying to do it?
> Because this looks like a mess of hard to understand code and there's 
> very likely a better way to do this.
>
> Those aliases would never be out of date with a static source.
> Your command has no source listed, so it will also never be out of 
> date..(after the first time, if the file t1 was actually built).
>
> -Bill
>
>
> On Sun, Jan 2, 2022 at 2:20 PM Bill Deegan <bill at baddogconsulting.com> 
> wrote:
>
>     also why **JUNK** in subject?
>
>     On Sun, Jan 2, 2022 at 2:20 PM Bill Deegan
>     <bill at baddogconsulting.com> wrote:
>
>         What output do you see when you run your example?
>
>
>         On Sun, Jan 2, 2022 at 7:56 AM Brad Kraemer
>         <computerpro_58 at hotmail.com> wrote:
>
>             Hello,
>
>             I filed a GitHub Issue
>             <https://github.com/SCons/scons/issues/4079> and got
>             bounced to this mailing list. So here we go again:
>
>             Value/Alias nodes (as created by the Alias() and Value()
>             functions/methods receptively) default to up-to-date.
>
>             SCons 4.1.0
>
>             Python 3.9
>
>             Installed from nixpkgs (NixOS, $ nix-env -iA nixos.scons)
>
>             Linux
>
>             Reproduction (SConstruct):
>
>             def print_target_1(target, source, env):
>                 print("Target 1 built")
>               
>             def print_alias_1(target, source, env):
>                 print("[I'm not getting called]")
>               
>             def print_alias_2(target, source, env):
>                 print("I'm getting called because of AlwaysBuild() workaround")
>               
>             t1 = Command("t1", [], Action(print_target_1, cmdstr=None))
>             Default(t1)
>               
>             v = Value("_")
>             a1 = Alias("a1", v, Action(print_alias_1, cmdstr=None))
>             a2 = Alias("a2", v, Action(print_alias_2, cmdstr=None))
>             Depends(t1, a1)
>             Depends(t1, a2)
>               
>             AlwaysBuild(a2)
>
>
>             Invoke via executing '$ scons' from the directory where
>             the above SConstruct file exists.
>
>
>             Thanks,
>
>             simplejack-src
>
>
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