On 22/10/13 16:35, Thomas Spatzier wrote:
Zane Bitter <zbit...@redhat.com> wrote on 22.10.2013 15:24:28:
From: Zane Bitter <zbit...@redhat.com>
To: openstack-dev@lists.openstack.org,
Date: 22.10.2013 15:27
Subject: Re: [openstack-dev] [Heat] HOT Software configuration proposal
On 22/10/13 09:15, Thomas Spatzier wrote:
BTW, the convention of properties being input and attributes being
output,
i.e. that subtle distinction between properties and attributes is not
really intuitive, at least not to me as non-native speaker, because I
used
to use both words as synonyms.
As a native speaker, I can confidently state that it's not intuitive to
anyone ;)
Phew, good to read that ;-)
We unfortunately inherited these names from the Properties section and
the Fn::GetAtt function in cfn templates. It's even worse than that,
because there's a whole category of... uh... things (DependsOn,
DeletionPolicy, &c.) that don't even have a name - I always have to
resist the urge to call them 'attributes' too.
So is this something we should try to get straight in HOT while we still
have the flexibility?
Y-yes. Provided that we can do it without making things *more*
confusing, +1. That's hard though, because there are a number of places
we have to refer to them, all with different audiences:
- HOT users
- cfn users
- Existing developers
- New developers
- Plugin developers
and using different names for the same thing can cause problems. My test
for this is: if you were helping a user on IRC debug an issue, is there
a high chance you would spend 15 minutes talking past each other because
they misunderstand the terminology?
Regarding properties/attributes for example, to me I would call both just
properties of a resource or component, and then I can write them or read
them like:
components:
my_component:
type: ...
properties:
my_prop: { get_property: [ other_component, other_component_prop ] }
other_component:
# ...
I.e. you write property 'my_prop' of 'my_component' in its properties
section, and you read property 'other_component_prop' of 'other_component'
using the get_property function.
... we can also call them attributes, but use one name, not two different
names for the same thing.
IMO inputs (Properties) and outputs (Fn::GetAtt) are different things
(and they exist in different namespaces), so -1 for giving them the same
name.
In an ideal world I'd like HOT to use something like get_output_data (or
maybe just get_data), but OTOH we have e.g. FnGetAtt() and
attributes_schema baked in to the plugin API that we can't really
change, so it seems likely to lead to developers and users adopting
different terminology, or making things very difficult for new
developers, or both :(
cheers,
Zane.
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