fmt.hh

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#pragma once
 
#include <iostream>
#include <string>
#include <boost/format.hpp>
#include "lix/libutil/ansicolor.hh"
 
// Explicit instantiation in fmt.cc
extern template class boost::basic_format<char>;
 
namespace nix {

std::string getStackTrace();

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;
}

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 {

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
    );
}

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);
    }
};
 
}

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)
try {
    boost::format f(fs);
    fmt_internal::setExceptions(f);
    (f % ... % args);
    return f.str();
} catch (boost::io::format_error & fe) { // NOLINT(lix-foreign-exceptions)
    // I don't care who catches this, we do not put up with boost format errors
    // Give me a stack trace and a core dump
    std::cerr << "nix::fmt threw format error. Original format string: '";
    std::cerr << fs << "'; number of arguments: " << sizeof...(args) << "\n";
    std::terminate();
}

class HintFmt
{
private:
    boost::format fmt;
 
public:
    // Moved out of line because it was instantiating the template below in
    // every file in the project.
    HintFmt(const std::string & literal);

    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::terminate();
        }
    } catch (boost::io::format_error & ex) { // NOLINT(lix-foreign-exceptions)
        // 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::terminate();
    }
 
    HintFmt(const HintFmt & hf) : fmt(hf.fmt) {}
 
    HintFmt & operator=(HintFmt const & rhs) = default;
 
    std::string str() const
    {
        return fmt.str();
    }
};
 
// Explicit instantiations in fmt.cc
extern template HintFmt::HintFmt(const std::string &, const Uncolored<std::string> &s);
extern template HintFmt::HintFmt(const std::string &, const std::string &s);
extern template HintFmt::HintFmt(const std::string &, const uint64_t &, const char * const &);
 
std::ostream & operator<<(std::ostream & os, const HintFmt & hf);
 
}