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#pragma once
///@file
#include <iostream>
#include <string>
#include <optional>
#include <boost/format.hpp>
// Darwin stdenv does not define _GNU_SOURCE but does have _Unwind_Backtrace.
#ifdef __APPLE__
#define BOOST_STACKTRACE_GNU_SOURCE_NOT_REQUIRED
#endif
#include <boost/stacktrace.hpp>
#include "ansicolor.hh"
namespace nix {
/**
* Values wrapped in this struct are printed in magenta.
*
* By default, arguments to `HintFmt` are printed in magenta. To avoid this,
* either wrap the argument in `Uncolored` or add a specialization of
* `HintFmt::operator%`.
*/
template<class T>
struct Magenta
{
Magenta(const T & s) : value(s) {}
const T & value;
};
template<class T>
std::ostream & operator<<(std::ostream & out, const Magenta<T> & y)
{
return out << ANSI_MAGENTA << y.value << ANSI_NORMAL;
}
/**
* Values wrapped in this class are printed without coloring.
*
* By default, arguments to `HintFmt` are printed in magenta (see `Magenta`).
*/
template<class T>
struct Uncolored
{
Uncolored(const T & s) : value(s) {}
const T & value;
};
template<class T>
std::ostream & operator<<(std::ostream & out, const Uncolored<T> & y)
{
return out << ANSI_NORMAL << y.value;
}
namespace fmt_internal {
/**
* Set the correct exceptions for `fmt`.
*/
inline void setExceptions(boost::format & fmt)
{
fmt.exceptions(
boost::io::all_error_bits ^ boost::io::too_many_args_bit ^ boost::io::too_few_args_bit
);
}
/**
* Helper class for `HintFmt` that supports the evil `operator%`.
*
* See: https://git.lix.systems/lix-project/lix/issues/178
*/
struct HintFmt
{
boost::format fmt;
template<typename... Args>
HintFmt(boost::format && fmt, const Args &... args) : fmt(std::move(fmt))
{
setExceptions(fmt);
(*this % ... % args);
}
template<class T>
HintFmt & operator%(const T & value)
{
fmt % Magenta(value);
return *this;
}
template<class T>
HintFmt & operator%(const Uncolored<T> & value)
{
fmt % value.value;
return *this;
}
boost::format into_format()
{
return std::move(fmt);
}
};
}
/**
* A helper for writing a `boost::format` expression to a string.
*
* These are (roughly) equivalent:
*
* ```
* fmt(formatString, a_0, ..., a_n)
* (boost::format(formatString) % a_0 % ... % a_n).str()
* ```
*
* However, when called with a single argument, the string is returned
* unchanged.
*
* If you write code like this:
*
* ```
* std::cout << boost::format(stringFromUserInput) << std::endl;
* ```
*
* And `stringFromUserInput` contains formatting placeholders like `%s`, then
* the code will crash at runtime. `fmt` helps you avoid this pitfall.
*/
inline std::string fmt(const std::string & s)
{
return s;
}
inline std::string fmt(const char * s)
{
return s;
}
template<typename... Args>
inline std::string fmt(const std::string & fs, const Args &... args)
{
boost::format f(fs);
fmt_internal::setExceptions(f);
(f % ... % args);
return f.str();
}
/**
* A wrapper around `boost::format` which colors interpolated arguments in
* magenta by default.
*/
class HintFmt
{
private:
boost::format fmt;
public:
/**
* Format the given string literally, without interpolating format
* placeholders.
*/
HintFmt(const std::string & literal) : HintFmt("%s", Uncolored(literal)) {}
/**
* Interpolate the given arguments into the format string.
*/
template<typename... Args>
HintFmt(const std::string & format, const Args &... args)
// Note the function try block.
try : fmt(fmt_internal::HintFmt(boost::format(format), args...).into_format())
{
if (this->fmt.remaining_args() != 0) {
// Abort. I don't want anything to catch this, I want a coredump.
std::cerr << "HintFmt received incorrect number of format args. Original format string: '";
std::cerr << format << "'; number of arguments: " << sizeof...(args) << "\n";
// And regardless of the coredump give me a damn stacktrace.
std::cerr << boost::stacktrace::stacktrace() << std::endl;
abort();
}
} catch (boost::io::format_error & ex) {
// Same thing, but for anything that happens in the member initializers.
std::cerr << "HintFmt received incorrect format string. Original format string: '";
std::cerr << format << "'; number of arguments: " << sizeof...(args) << "\n";
std::cerr << boost::stacktrace::stacktrace() << std::endl;
abort();
}
HintFmt(const HintFmt & hf) : fmt(hf.fmt) {}
std::string str() const
{
return fmt.str();
}
};
std::ostream & operator<<(std::ostream & os, const HintFmt & hf);
}
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