www.digitalmars.com         C & C++   DMDScript  

digitalmars.D.bugs - [Issue 7675] New: std.format needs better exception messages

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=7675

           Summary: std.format needs better exception messages
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: Phobos
        AssignedTo: nobody puremagic.com
        ReportedBy: andrej.mitrovich gmail.com



17:53:14 PST ---
import std.string;

void main()
{
    string res = format("%s %s", 1);
}

std.format.FormatException std\format.d(62): format error

format() should verify that the count of parameters matches the format
specifier and give a nice error message like this:

std.format.FormatException std\format.d(62): format error: Expected 2
parameters, got 1.

format() is one of the most used functions in Phobos so I think this is pretty
important.

-- 
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
Mar 08 2012
next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=7675




09:54:34 PDT ---
If anyone else is annoyed by this you can use a workaround like this:

/** Workaround for Issue 7675 - std.format needs better exception messages */
string safeFmt(string file = __FILE__, int line = __LINE__, T...)(string fmt, T
args)
{
    auto specCount = count(fmt, "%s");
    enforce(specCount == T.length, 
            new Exception(format("Arg count %s doesn't match spec count %s.",
T.length, specCount), file, line));
    return format(fmt, args);
}

That implies using %s exclusively and it only throws on argument count
mismatch, but it's still a shitload better than "Error occurred somewhere, have
fun debugging!".

Throwing exceptions in Phobos with no information on what went wrong should be
*banned*.

-- 
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
May 26 2012
prev sibling next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=7675


bearophile_hugs eml.cc changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bearophile_hugs eml.cc






     enforce(specCount == T.length, 
             new Exception(format("Arg count %s doesn't match spec count %s.",
 T.length, specCount), file, line));


Andrei wants formatted printing to be sloppy, so currently this doesn't raise
an error:

import std.string;
void main() {
    string res = format("%s ", 1, 2);
}

-- 
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
May 26 2012
prev sibling next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=7675




12:42:38 PDT ---


 Andrei wants formatted printing to be sloppy, so currently this doesn't raise
 an error..


Right, but the OP code does raise an exception except it gives absolutely no
information whatsoever on what went wrong. Reading a stack trace of a dozen
template instantiations doesn't help either.

-- 
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
May 26 2012
prev sibling next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=7675


Andrej Mitrovic <andrej.mitrovich gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |WORKSFORME



16:11:25 PST ---
The situation seems to be better now:

import std.string;
void main()
{
    string res = format("%s %s", 1);
}


 std.format.FormatException D:\dmd-git\dmd2\windows\bin\..\..\src\phobo
\std\format.d(431): Orphan format specifier: %%s %s


Slightly confusing message, as it thought it was going to print '%s' but it
prints the entire string.

And the other message:

import std.string;
void main()
{
    string res = format("%s %s", 1, 2, 3);
}


 std.format.FormatException D:\dmd-git\dmd2\windows\bin\..\..\src\phobos
std\string.d(2536): Orphan format arguments: args[2..3]


I'm quite satisfied that this was implemented. Although the stack trace still
sucks as I've yet to get proper line numbers. 

But at least I don't have to count the specifiers in a wrapper function, I just
have to catch FormatExceptions:

string safeFmt(string file = __FILE__, size_t line = __LINE__, Args...)(string
fmt, Args args)
{
    try
    {
        return format(fmt, args);
    }
    catch (FormatException exc)
    {
        exc.file = file;
        exc.line = line;
        throw exc;
    }
}

void main()
{
    auto x = safeFmt("%s", 1, 2);
}

How great is that?

-- 
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
Jan 24 2013
prev sibling next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=7675


Lukasz Wrzosek <luk.wrzosek gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |luk.wrzosek gmail.com



PDT ---
Why this sample compiles fine if it always frows an exception ?

import std.string;

void main()
{
    string res = format("%s %s", 1);
}

-- 
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
May 22 2013
prev sibling next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=7675




14:39:28 PDT ---


 Why this sample compiles fine if it always throws an exception ?


Because the string argument is passed at runtime.

-- 
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
May 22 2013
prev sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=7675




PDT ---
I know that already, but why it was written like that?
It would be useful to have this kind of error thrown at compile time, wouldn't
it"

-- 
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
May 24 2013