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Addition format() testing #98

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0170dac
Addition format() testing
MungoG Nov 20, 2025
c5e2465
Merge branch 'develop' into issue-89-additional-format-testing
MungoG Dec 1, 2025
8342b86
use fmtlib and std::format style escaping/errors and add tests
MungoG Dec 1, 2025
4998132
use exception helpers
MungoG Dec 4, 2025
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80 changes: 63 additions & 17 deletions include/boost/beast2/format.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -46,21 +46,55 @@ struct format_impl
next()
{
has_placeholder = false;
bool unmatched_open = false;
bool unmatched_close = false;
while (p != end)
{
if (*p++ != '{')
continue;
if (p == end)
break;
if (*p++ == '}')
if(unmatched_open)
{
if(*p == '{')
{
p++;
core::string_view seg(p0, (p - 1) - p0);
p0 = p;
return seg;
}
if(*p == '}')
{
p++;
core::string_view seg(p0, (p - 2) - p0);
p0 = p;
has_placeholder = true;
return seg;
}
throw std::runtime_error("invalid format string, unmatched {");
}
if(unmatched_close)
{
if(*p == '}')
{
p++;
core::string_view seg(p0, (p - 1) - p0);
p0 = p;
return seg;
}
throw std::runtime_error("invalid format string, unmatched }");
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@vinniefalco vinniefalco Dec 2, 2025

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This seems kind of harsh... throwing? Anyway if we are going to throw we need to use the helpers in detail/except.hpp.

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@MungoG MungoG Dec 4, 2025

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Throwing is consistent with the behaviour of both fmtlib and std::format. Code that works with this implementation therefore has a clear migration path in the future.
Will change to use the helpers.

}
if (*p == '{')
{
unmatched_open = true;
}
if(*p == '}')
{
core::string_view seg(
p0, (p - 2) - p0);
p0 = p;
has_placeholder = true;
return seg;
unmatched_close = true;
}
p++;
}
if (unmatched_open)
throw std::runtime_error("invalid format string, unmatched {");
if(unmatched_close)
throw std::runtime_error("invalid format string, unmatched }");

core::string_view seg(
p0, end - p0);
p0 = end;
Expand All @@ -71,10 +105,14 @@ struct format_impl
void do_arg(Arg const& arg)
{
core::string_view seg = next();
if (seg.size())
os.write(seg.data(), static_cast<
std::streamsize>(seg.size()));
if (has_placeholder)
while(seg.size())
{
os.write(seg.data(), static_cast<std::streamsize>(seg.size()));
if(has_placeholder)
break;
seg = next();
}
if(has_placeholder)
os << arg;
};

Expand All @@ -83,9 +121,17 @@ struct format_impl
{
using expander = int[];
(void)expander{0, (do_arg(args), 0)...};
if (p0 < end)
os.write(p0, static_cast<
std::streamsize>(end - p0));

core::string_view seg;
do
{
seg = next();
if(has_placeholder)
throw std::runtime_error("too few arguments");
if(seg.size())
os.write(seg.data(), static_cast<std::streamsize>(seg.size()));
}
while(seg.size());
}
};

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45 changes: 36 additions & 9 deletions test/unit/format.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -28,22 +28,49 @@ struct format_test
BOOST_TEST_EQ(s, match);
}

template<class... Args>
void e(
core::string_view match,
core::string_view fs,
Args const&... args)
{
BOOST_TEST_THROWS(f(match, fs, args...), std::runtime_error);
}

void run()
{
// Bad format strings, string arg.
e("{}", "{}");
e("{", "{");
e("}", "}");
e("}{", "}{");
e("{", "{", "x");
e("}", "}", "x");
e("}{", "}{", "x");
e("{", "{", "x");
e("}", "}", "x");
e("}{", "}{", "x");
e("1{}2{}3","1{}2{}3");
e("1a2{}3", "1{}2{}3", "a");

// Good format strings, string arg.
f("x", "x");
f("{}", "{}");
f("{", "{");
f("}", "}");
f("}{", "}{");
f("{", "{{");
f("}", "}}");
f("}{", "}}{{");
f("x", "x");
f("x", "{}", "x");
f("{", "{", "x");
f("}", "}", "x");
f("}{", "}{", "x");
f("1{}2{}3","1{}2{}3");
f("1a2{}3", "1{}2{}3", "a");
f("x", "{}", "x");
f("{", "{{", "x");
f("}", "}}", "x");
f("}{", "}}{{", "x");
f("1a2b3", "1{}2{}3", "a", "b");
f("1a2b3", "1{}2{}3", "a", "b", "c");
f("hello world!", "hello {}!", "world");
f("hello world! {} ", "hello {}! {{}} ", "world");

// Good format string, char arg
f("x", "{}", 'x');
}
};

Expand Down
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