AWS::Core::Data::List is not an array, and doesn't act like one about aws-sdk-ruby HOT 5 CLOSED

Sorry, gave you the wrong link: https://github.com/aws/aws-sdk-ruby/blob/master/lib/aws/core/data.rb#L230

Fundamentally this lies, because methods defined on Object will never hit your method missing proxy, and therefore in this case I've duplicated AWS::Core::Data::List, which of course does not duplicate the array that it's delegating to.

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To clarify: it seems like the underlying issue here is that calling #dup on Data::List will not perform a deep copy-- that and the fact that our docs are misleading in reporting an "Array" return rather than the proper Data::List class that is returned (which actually wraps the Array). I think we can fix both of those things, so that a) the docs don't refer to the returned instance data as a plain array, and, b) we can better handle dup to perform a deep copy so they work better when a user wants to mutate the original object.

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The AWS::Core::Data classes were added quite a while ago. The client classes (like AWS::EC2::Client) used to construct responses where the values where dynamically created objects with methods punched onto them. This proved to be a performance bottle neck. To address the performance issues, the client response data objects were changed to plain old nested hashes and arrays.

AWS::Core::Data and AWS::Core::Data::List were added to provide a backwards compatible interface for accessing response data.

resp = ec2.client.describe_regions

# deprecated interface, currently handled via AWS::Core::Data
resp.region_info[0].region_name

# preferred access style
resp[:region_info].first[:region_name]

Accessing response data via #[] returns plain old hashes and arrays. Accessing response attributes via named methods return these same structures wrapped. Method style access is deprecated and will not exist in version 2. Unfortunately some sections of the SDK still access response data via the old interfaces. The AWS::EC2::Instance#create method is one such section. Unfortunately this abstraction leaked out because of the call to #map in this method.

I agree with Loren, the core data abstractions can be improved (to prevent this issue). That said, I consider this also a bug. The #create method previously did return an array and the documentation should probably not change. Ideally all such uses of response objects through method missing (that returns a core data object) should be removed.

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Commit 79cbc73 should resolve the immediate issue of AWS::EC2::InstanceCollection#create not returning an actual array. Changes still need to be made to the core data classes.

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I pushed a branch with a proposed change to the core data classes (core-data-fix branch). You can view the changes here: bfc4dc6.

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