http://d.puremagic.com/issues/show_bug.cgi?id=2370

           Summary: Version statement enhancement: versioned identifiers
           Product: D
           Version: unspecified
          Platform: PC
        OS/Version: Windows
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: DMD
        AssignedTo: bugzilla@digitalmars.com
        ReportedBy: snake.scaly@gmail.com


I propose version identifiers to have a numeric value and to add the following version statement syntax:

VersionCondition:
  version ( Identifier, Integer )

This version condition is satisfied when the Identifier's value is equal or greater than the Integer.  This way, the code in

version (D_Version, 2)
{
...
}

will be compiled only when the compiler version is 2 or greater.  The version specification syntax can be

VersionSpecification:
  version = Identifier ( Integer ) ;


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http://d.puremagic.com/issues/show_bug.cgi?id=2370





------- Comment #1 from jarrett.billingsley@gmail.com  2008-09-22 22:27 -------
Please please please.  It seems odd that such an obvious use of preprocessor macros for versioning was not carried forward into D.


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http://d.puremagic.com/issues/show_bug.cgi?id=2370





------- Comment #2 from benoit@tionex.de  2008-09-23 03:41 -------
This would have helped me a lot in the past.


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http://d.puremagic.com/issues/show_bug.cgi?id=2370


shro8822@vandals.uidaho.edu changed:

           What    |Removed                     |Added
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                 CC|                            |shro8822@vandals.uidaho.edu




------- Comment #3 from shro8822@vandals.uidaho.edu  2008-09-23 13:34 -------

Vote += Lots


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http://d.puremagic.com/issues/show_bug.cgi?id=2370


brunodomedeiros+bugz@gmail.com changed:

           What    |Removed                     |Added
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                 CC|                            |brunodomedeiros+bugz@gmail.c
                   |                            |om




------- Comment #4 from brunodomedeiros+bugz@gmail.com  2008-10-03 10:04 -------
Like I said in the original thread, isn't it enough to have:
  version(D_Version_2OrAbove) { ...
?
Or just
  version(D_Version1) {
    ...
  } else {
    //version 2 or above here...
  }
?
It doesn't seem this feature is justified.


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http://d.puremagic.com/issues/show_bug.cgi?id=2370





------- Comment #5 from snake.scaly@gmail.com  2008-10-03 10:53 -------
(In reply to comment #4)
> Like I said in the original thread, isn't it enough to have:
>   version(D_Version_2OrAbove) { ...
> ?
> Or just
>   version(D_Version1) {
>     ...
>   } else {
>     //version 2 or above here...
>   }
> ?
> It doesn't seem this feature is justified.

Imagine I've got MyLib v.21.  There was nice API introduced in v.17 and I have a special cased code which should work from version 17 on. In my approach:

module myapp;
import mylib;
version(MyLib, 17)
{
  NiftyMyLibCall();
}
else
{
  ...lots of code...
}

module mylib;
version = MyLib(21);

In your approach I'm either going to have 21 version statements in mylib which
is tedious, error-prone and is hardly automated, or I must have 5 version
clauses in my source which all mix in the same piece of code
and I must add new version clause every time a new version of lib is published.


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http://d.puremagic.com/issues/show_bug.cgi?id=2370





------- Comment #6 from brunodomedeiros+bugz@gmail.com  2008-10-03 11:31 -------
If you add a specific feature in a given version, it's best (clearer) to add a:
  version = NiftyMyLibCallAvailable;
and then use:
  version(NiftyMyLibCallAvailable)
  {
    NiftyMyLibCall();
  }
instead of version numbers.

In any case, when releasing a new version:
Your approach:
  * go to the 'version = MyLibVersion(20);' statement
  * change it to 'version = MyLibVersion(21);'

My approach:
  * go to the 'version = MyLibVersion20OrAbove;' statement
  * add a 'version = MyLibVersion21OrAbove;' statement

How is my approach any more tedious, error-prone, or less automated? They are both one line changes you have to make (mine has an extra copy&paste), and they are both dead easy to make. My approach may end up with more code written, but that's hardly ever more error-prone, since that code is not supposed to change or be maintained (one doesn't usually downgrade the version number of a lib).


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http://d.puremagic.com/issues/show_bug.cgi?id=2370





------- Comment #7 from snake.scaly@gmail.com  2008-10-03 15:46 -------
(In reply to comment #6)
> If you add a specific feature in a given version, it's best (clearer) to add a:
>   version = NiftyMyLibCallAvailable;
> and then use:
>   version(NiftyMyLibCallAvailable)
>   {
>     NiftyMyLibCall();
>   }
> instead of version numbers.

Is there *any* library around that has a version/#define for every single interface and every single change in that interface?  I don't think so, it's just not feasible.

> In any case, when releasing a new version:
> Your approach:
>   * go to the 'version = MyLibVersion(20);' statement
>   * change it to 'version = MyLibVersion(21);'
> 
> My approach:
>   * go to the 'version = MyLibVersion20OrAbove;' statement
>   * add a 'version = MyLibVersion21OrAbove;' statement
> 
> How is my approach any more tedious, error-prone, or less automated? They are both one line changes you have to make (mine has an extra copy&paste), and they are both dead easy to make. My approach may end up with more code written, but that's hardly ever more error-prone, since that code is not supposed to change or be maintained (one doesn't usually downgrade the version number of a lib).

A version number in one particular place can be replaced by a script, or by a version control system.  It's significantly harder to add a line automatically.

Though adding a line for every version is definitely much better than adding a version statement for every interface change.


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http://d.puremagic.com/issues/show_bug.cgi?id=2370





------- Comment #8 from shro8822@vandals.uidaho.edu  2008-10-03 15:55 -------
Several of the comments seem to be forgetting that "version = bob" in an imported file has no effect on "version(bob)" statements in the importing file.


importer.d:

  import imported;
  version(bob) { pragma(msg,"bob"); }
  else { pragma(msg,"!bob"); }

imported.d:

  version = bob;

output:

  !bob


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http://d.puremagic.com/issues/show_bug.cgi?id=2370





------- Comment #9 from snake.scaly@gmail.com  2008-10-03 16:10 -------
(In reply to comment #8)
> Several of the comments seem to be forgetting that "version = bob" in an imported file has no effect on "version(bob)" statements in the importing file.

You're right.  This is a very strange and undocumented behavior.  Well, this adds more value to my proposal: writing 21 version statements in command line is... well, tedious.


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