[Issue 10291] New: formattedWrite() to an Appender fails silently after Appender.clear()

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=10291

           Summary: formattedWrite() to an Appender fails silently after
                    Appender.clear()
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Phobos
        AssignedTo: nobody at puremagic.com
        ReportedBy: jared at economicmodeling.com


--- Comment #0 from Jared Miller <jared at economicmodeling.com> 2013-06-07 14:19:36 PDT ---
After calling clear() on a std.array.Appender, formattedWrite() using that
appender fails silently. Calling the appender's put() method once after a
clear() is a workaround. Tested on DMD 2.062.

Example:
----
import std.stdio, std.array, std.format, std.string;

void main()
{    
    // FIRST EXAMPLE: use only put().
    auto a = appender!string;
    a.put( format("%d", 1) );
    writeln(a.data);
    a.clear();
    // put() after clear() is OK.
    a.put( format("%d", 2) );
    writeln(a.data);
    assert(a.data == "2");

    // SECOND EXAMPLE: use only formattedWrite().
    auto b = appender!string;
    b.reserve(128);
    formattedWrite(b, "%d", 1);
    writeln(b.data);
    assert(b.data == "1");
    b.clear();
    // formattedWrite() after clear() does not work.
    formattedWrite(b, "%d", 2); // <-- FAILS SILENTLY
    writeln(b.data); // "" (writes empty string)
    assert(b.data == ""); // this should not pass, but it does.
    // You have to call put() on appender before formattedWrite() works again.
    b.put("");
    formattedWrite(b, "%d", 3);
    writeln(b.data);
    assert(b.data == "3");
}
----

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