Make required types actually required by the Haskell type system
----------------------------------------------------------------
Key: THRIFT-908
URL: https://issues.apache.org/jira/browse/THRIFT-908
Project: Thrift
Issue Type: Bug
Components: Haskell - Compiler, Haskell - Library
Environment: ghc 6.12.3 on Mac OS X 10.6 (Haskell Platform 2010.2)
Darwin -- 10.4.0 Darwin Kernel Version 10.4.0: Fri Apr 23 18:28:53 PDT 2010;
root:xnu-1504.7.4~1/RELEASE_I386 i386
The Glorious Glasgow Haskell Compilation System, version 6.12.3
Reporter: Christian Lavoie
Currently Haskell bindings consider all struct fields to be optional by having
all struct fields be "Maybe $field". This patch removes that Maybe for required
fields.
THIS BREAKS EXISTING CODE.
It's also probably incomplete -- I haven't looked too carefully yet at what
happens on the server side if it tries to parse out an incomplete struct
definition:
{noformat}
struct myStruct {
1: required byte foo,
}
{noformat}
became after some code changes
{noformat}
struct myStruct {
1: optional byte foo,
}
{noformat}
And code generated for the first version is asked to read a struct from the
second version where foo is missing.
I suspect after this patch the Haskell server commits hara-kiri trying to
evaluate {{undefined}} _outside_ of the thrift generated code (so the client
could would receive an error for something that the thrift generated code
should have noticed as wrong). This is clearly inadequate.
Consider this bug a thought experiment / request for comments until I validate
that the patch is complete. It will still break existing code.
First and foremost:
# Thoughts?
# What would be an acceptable way to handle the case described above for other
Haskell users? Break the current interface some more by returning some error
type (Either $struct $errMessags?). Throw a Haskell exception?
# How do the other bindings handle parsing invalid data off the network?
# The generator and generated code is fairly painful to read. Would the powers
that be welcome a cleanup patch that moves as much of the t_hs_generator.cpp
code to a boost::format-style system that uses template strings that look like
Haskell code, and reformats the output to be indented, proper style Haskell
code as much as possible?
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