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From "Randy Abernethy (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (THRIFT-2464) Transition cpp_type and cpp_include keywords to compiler annotations
Date Thu, 03 Jan 2019 17:38:00 GMT

    [ https://issues.apache.org/jira/browse/THRIFT-2464?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16733271#comment-16733271
] 

Randy Abernethy commented on THRIFT-2464:
-----------------------------------------

This is covered pretty thoroughly in chapter 5 of the Programmer's Guide to Apache Thrift.
I agree Thrift should supply standard cross platform types that work across all languages.
However there are multiple layers of abstraction in Thrift:
 # IDL - the conceptual types
 # wire - the protocol based serialization of the types
 # language - the language specific implementation of the types

It is in #3 that the impl may need to be (or could benefit from) being tweaked. The IDL compiler
might generate a Java TreeMap for a Thrift Map or it might generate a HashMap. We can not
say which is the right answer without a use case.

It is also important to note that the language impl has (must have) no impact on the wire
or conceptual type representations. Adding types to the IDL or wire layers is a breaking Thrift
wide interface change and I think should be avoided unless tremendous benefit is imparted.
On the other hand, changing impl types is by definition an implementation detail that no one
on the other side of the RPC should care about.

In short, I agree with [~jking3] that the cpp_type and cpp_include keywords should be removed
but the functionality should be preserved through Thrift annotations. So my vote is that until
we have the annotations working we do not remove the keywords.

The annotation solution would look something like this:

{{(cpp.include = "unordered_map")}}

{{exception BadFishes {}}
{{    1: map (cpp.type "std::unordered_map<string, int16_t>") <string, i16> 
fish_errors}}
{{}}}

Should be an easy change.

 

> Transition cpp_type and cpp_include keywords to compiler annotations
> --------------------------------------------------------------------
>
>                 Key: THRIFT-2464
>                 URL: https://issues.apache.org/jira/browse/THRIFT-2464
>             Project: Thrift
>          Issue Type: Improvement
>          Components: Compiler (General)
>    Affects Versions: 0.9.2
>         Environment: C++
>            Reporter: Randy Abernethy
>            Assignee: Randy Abernethy
>            Priority: Minor
>
> The cpp_type and cpp_include keywords provide a useful feature but are language specific.
In keeping with the trend of moving the interface language to a clean cross implementation
language abstraction, these two keywords should be transitioned to annotations.



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