[jira] [Created] (PROTON-1216) c++: proton::coerce() should allow conversion from binary.

["Alan Conway (JIRA)" <ji...@apache.org>]

Alan Conway created PROTON-1216:
-----------------------------------

             Summary: c++: proton::coerce<std::string>() should allow conversion from binary.
                 Key: PROTON-1216
                 URL: https://issues.apache.org/jira/browse/PROTON-1216
             Project: Qpid Proton
          Issue Type: Bug
          Components: cpp-binding
    Affects Versions: 0.12.2
            Reporter: Alan Conway
            Assignee: Alan Conway
             Fix For: 0.13.0


proton::coerce<std::string> should convert a binary value to a std::string. The documentation also needs clarification: coerce should allow exactly those conversions that are allowed as implicit C++ conversions.

Issue raised in excellent bug report on the user list http://qpid.2158936.n2.nabble.com/Proton-C-0-13-x-decode-binary-type-tp7644510p7644747.html text follows:

proton::coerce (both forms) currently throws the same
exception as proton::get, as does value.as_string(), although that doesn't
appear to be in the public API. Not sure what 'd' was in the d>>b  example,
but got a version working using value.get<std::binary>() and an implicit
cast to std::string.

To reproduce...

#include <proton/value.hpp>
#include <proton/binary.hpp>
#include <proton/error.hpp>
#include <iostream>

template<typename Lambda>
void expect_exception ( Lambda f )
{
  try
  {
    f();
    std::cout << "*** FAIL (expected conversion error) ***" << std::endl;
  }
  catch ( const proton::conversion_error& e )
  {
    std::cout << "PASS" << std::endl;
  }
}

template<typename Lambda>
void expect_value ( const std::string& expected, Lambda f )
{
  try
  {
    std::cout << (f() == expected ? "PASS" : "*** FAIL (wrong value) ***")
<< std::endl;
  }
  catch ( const proton::conversion_error& e )
  {
    std::cout << "*** FAIL (conversion error) ***" << std::endl;
  }

}

int main()
{

  std::string expected = "Hello World!";
  proton::value value = proton::binary(expected);

  expect_exception(      [=] { return value.get<std::string>();                
});
  expect_exception(      [=] { return proton::get<std::string>(value);         
});
  expect_exception(      [=] { std::string result;
proton::get<std::string>(value); return result; });

  expect_value(expected, [=] () -> std::string { return
value.get<proton::binary>(); } );

  // The following currently fail under 0.13.x
  expect_value(expected, [=] { return value.as_string();                       
});
  expect_value(expected, [=] { return proton::coerce<std::string>(value);      
});
  expect_value(expected, [=] { std::string result;
proton::coerce<std::string>(value, result); return result; });
  
}




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