[Scons-users] `__lib_either_version_flag` returning `None` triggers `NameError`

[Mats Wichmann]

On 4/14/24 11:04, Sye van der Veen wrote:
> I call `SetAllowableExceptions()` in my build files to ensure that I set 
> all applicable build variables for my targets. I then set variables I 
> don't currently need to the empty string, to avoid the resulting 
> `NameError`s.
> 
> After a recent update to Scons 4.7.0, I was getting a `NameError` 
> stating that `__libversionflags` was undefined. This variable is 
> implemented as a function, and the docstring states: `if version_var is 
> not empty, returns env[flags_var], otherwise returns None`.
...
> I propose that `__libversionflags` be modified to return the empty 
> string if `version_var` is empty. Note that a similar issue exists for 
> `__lib_either_version_flag` in the same file; I propose the same change 
> here too.

The change is obviously simple enough, like:

@@ -690,7 +690,7 @@ def __libversionflags(env, version_var, flags_var):
      """
      try:
          if env.subst('$' + version_var):
-            return env[flags_var]
+            return env.get(flags_var, "")
      except KeyError:
          pass
      return None


But curious why it specifically is documented to return None in this 
case, and what's changed to cause you a problem - the code doesn't look 
to have been been changed in this area for several years.  What version 
were you running where this didn't cause problems? (consider this the 
investigative phase :-) )