[Scons-users] CPPDEFINES Unexpected Behavior

[Evan Driscoll]

On 04/11/2013 03:27 PM, Dirk Bächle wrote:

> Rob,

>

> On 11.04.2013 21:35, Managan, Rob wrote:

>> Dirk,

>>

>> I don't think it is quite that simple. I agree with you for these two 

>> cases:

>>

>> [...]

>> However,

>> env = Environment(CPPDEFINES={'def1':23, 'def2':None})

>> env.AppendUnique(CPPDEFINES=['def3=4'])

>>

>

> this is a contrived example indeed. I fail to see what would be the 

> expected output of a list appended to a dict. And what should happen 

> in the opposite case? Do we really want to support all these corner 

> cases, or wouldn't a note in the docs help, telling the user to stay 

> consistent and use all lists or all dicts only?


Just to reiterate my previous email:  IMO, the mixed-type appending is a 
red herring.


It is surprising to me that
     env["CPPDEFINES"] = { key : value }
and
     env["CPPDEFINES"] = [ (key, value) ]
produce the same answer in all cases *except* when value is None. (In 
fact, I'm doubly surprised as I'd have expected a dictionary CPPDEFINES 
to just be converted to a list in the implementation.)

Changing *that* behavior, which seems to me to be desirable anyway, 
seems likely to fix Rob's behavior along the way as a side effect. 
Though I also agree the mix of dicts and lists doesn't seem like a good 
idea to me. :-)

Evan
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