lix/tests/errors/main.cc

#include "../../src/libutil/error.hh"
#include "../../src/libexpr/nixexpr.hh"

#include <iostream>
#include <optional>

int main()
{
    using namespace nix;

    // In each program where errors occur, this has to be set.
    ErrorInfo::programName = std::optional("error-test");

    // There are currently four error types:
    //
    // 			ProgramError, ProgramWarning, NixLangError, NixLangWarning.
    //
    // Each error type is created with a specific sequence of builder functions.
    // Unlike with a constructor, each parameter is clearly named.
    // If the sequence of function calls isn't followed, then there's a type
    // error. This should make for a consistent look in the code when errors are
    // created.

    // ProgramError takes name, description, and an optional hint.
    printErrorInfo( ProgramError()
                    .name("name")
                    .description("error description")
                    .nohint()
                  );

    // ProgramWarning takes name, description, and an optional hint.
    // The hint is in the form of a hintfmt class, which wraps boost::format(),
    // and makes all the substituted text yellow.
    printErrorInfo( ProgramWarning()
                    .name("warning name")
                    .description("warning description")
                    // the templated value, 'warning', is automatically colored yellow.
                    .hint(hintfmt("there was a %1%", "warning")) 
                  );

    /*
      // some invalid errors:

      // type error: no hint function.
      ProgramError()
        .name("name")
        .description("error description");

      // type error:  description before name.
      ProgramError()
        .description("error description")
        .name("name")
        .nohint();

      // type error: hint function with regular boost format, not special
      hintfmt. ProgramError() .description("error description") .name("name")
        .hint(format("there was a %1%") % "warning");
    */

    // NixLangWarning adds nix file, line number, column range, and the lines of
    // code where a warning occurred.

    SymbolTable testTable;
    auto problem_symbol = testTable.create("problem");

    printErrorInfo(NixLangWarning()
                   .name("warning name")
                   .description("warning description")
                   .pos(Pos(problem_symbol, 40, 13))
                   .linesOfCode(std::nullopt,
                                "this is the problem line of code",
                                std::nullopt)
                   .hint(hintfmt("this hint has %1% templated %2%!!", "yellow" , "values")));

    // NixLangError is just the same as NixLangWarning, except for the Error
    // flag.
    printErrorInfo(NixLangError()
                   .name("error name")
                   .description("error description")
                   .pos(Pos(problem_symbol, 40, 13))
                   .linesOfCode(std::optional("previous line of code"),
                                "this is the problem line of code",
                                std::optional("next line of code"))
                   .hint(hintfmt("this hint has %1% templated %2%!!", "yellow", "values")));

    return 0;
}