meson: install systemd files

Change-Id: Idacf602fd379c82a051f00df2293cb02c8b286d4

meson.build

@@ -214,6 +214,9 @@ deps += gtest
 toml11 = dependency('toml11', version : '>=3.7.0', required : true)
 deps += toml11
 
+nlohmann_json = dependency('nlohmann_json', required : true)
+deps += nlohmann_json
+
 #
 # Build-time tools
 #
@@ -244,13 +247,12 @@ bison = find_program('bison')
 flex = find_program('flex')
 
 # This is how Nix does generated headers...
+# other instances of header generation use a very similar command.
 # FIXME(Qyriad): do we really need to use the shell for this?
+gen_header_sh = 'echo \'R"__NIX_STR(\' | cat - @INPUT@ && echo \')__NIX_STR"\''
 gen_header = generator(
   bash,
-  arguments : [
-    '-c',
-    'echo \'R"__NIX_STR(\' | cat - @INPUT@ && echo \')__NIX_STR"\'',
-  ],
+  arguments : [ '-c', gen_header_sh ],
   capture : true,
   output : '@PLAINNAME@.gen.hh',
 )
@@ -352,13 +354,10 @@ if get_option('profile-build').require(meson.get_compiler('cpp').get_id() == 'cl
 endif
 
 subdir('src')
+subdir('scripts')
+subdir('misc')
 
 if enable_tests
-  # Just configures `scripts/nix-profile.sh.in` (and copies the original to the build directory).
-  # Done as a subdirectory to convince Meson to put the configured files
-  # in `build/scripts` instead of just `build`.
-  subdir('scripts')
-
   subdir('tests/unit')
   subdir('tests/functional')
 endif

meson.options

@@ -39,7 +39,7 @@ option('store-dir', type : 'string', value : '/nix/store',
   description : 'path of the Nix store',
 )
 
-option('state-dir', type : 'string', value : '/nix/var/nix',
+option('state-dir', type : 'string', value : '/nix/var',
   description : 'path to store state in for Nix',
 )
 

misc/bash/meson.build

@@ -0,0 +1,8 @@
+configure_file(
+  input : 'completion.sh',
+  output : 'nix',
+  install : true,
+  install_dir : datadir / 'bash-completion/completions',
+  install_mode : 'rw-r--r--',
+  copy : true,
+)

misc/fish/meson.build

@@ -0,0 +1,8 @@
+configure_file(
+  input : 'completion.fish',
+  output : 'nix.fish',
+  install : true,
+  install_dir : datadir / 'fish/vendor_completions.d',
+  install_mode : 'rw-r--r--',
+  copy : true,
+)

misc/meson.build

@@ -0,0 +1,5 @@
+subdir('bash')
+subdir('fish')
+subdir('zsh')
+
+subdir('systemd')

misc/systemd/meson.build

@@ -0,0 +1,25 @@
+foreach config : [ 'nix-daemon.socket', 'nix-daemon.service' ]
+  configure_file(
+    input : config + '.in',
+    output : config,
+    install : true,
+    install_dir : prefix / 'lib/systemd/system',
+    install_mode : 'rw-r--r--',
+    configuration : {
+      'storedir' : store_dir,
+      'localstatedir' : state_dir,
+      'bindir' : bindir,
+    },
+  )
+endforeach
+
+configure_file(
+  input : 'nix-daemon.conf.in',
+  output : 'nix-daemon.conf',
+  install : true,
+  install_dir : prefix / 'lib/tmpfiles.d',
+  install_mode : 'rw-r--r--',
+  configuration : {
+    'localstatedir' : state_dir,
+  },
+)

misc/zsh/meson.build

@@ -0,0 +1,10 @@
+foreach script : [ [ 'completion.zsh', '_nix' ], [ 'run-help-nix' ] ]
+  configure_file(
+    input : script[0],
+    output : script.get(1, script[0]),
+    install : true,
+    install_dir : datadir / 'zsh/site-functions',
+    install_mode : 'rw-r--r--',
+    copy : true,
+  )
+endforeach

scripts/meson.build

@@ -1,3 +1,5 @@
+# configures `scripts/nix-profile.sh.in` (and copies the original to the build directory).
+# this is only needed for tests, but running it unconditionally does not hurt enough to care.
 configure_file(
   input : 'nix-profile.sh.in',
   output : 'nix-profile.sh',
@@ -12,3 +14,16 @@ configure_file(
   output : 'nix-profile.sh.in',
   copy : true,
 )
+
+foreach rc : [ '.sh', '.fish', '-daemon.sh', '-daemon.fish' ]
+  configure_file(
+    input : 'nix-profile' + rc  + '.in',
+    output : 'nix' + rc,
+    install : true,
+    install_dir : sysconfdir / 'profile.d',
+    install_mode : 'rw-r--r--',
+    configuration : {
+      'localstatedir': state_dir,
+    },
+  )
+endforeach

src/build-remote/build-remote.cc

@@ -185,16 +185,6 @@ static int main_build_remote(int argc, char * * argv)
                         std::cerr << "# postpone\n";
                     else
                     {
-                        // build the hint template.
-                        std::string errorText =
-                            "Failed to find a machine for remote build!\n"
-                            "derivation: %s\nrequired (system, features): (%s, [%s])";
-                        errorText += "\n%s available machines:";
-                        errorText += "\n(systems, maxjobs, supportedFeatures, mandatoryFeatures)";
-
-                        for (unsigned int i = 0; i < machines.size(); ++i)
-                            errorText += "\n([%s], %s, [%s], [%s])";
-
                         // add the template values.
                         std::string drvstr;
                         if (drvPath.has_value())
@@ -202,19 +192,30 @@ static int main_build_remote(int argc, char * * argv)
                         else
                             drvstr = "<unknown>";
 
-                        auto error = HintFmt::fromFormatString(errorText);
-                        error
-                            % drvstr
-                            % neededSystem
-                            % concatStringsSep<StringSet>(", ", requiredFeatures)
-                            % machines.size();
+                        std::string machinesFormatted;
 
-                        for (auto & m : machines)
-                            error
-                                % concatStringsSep<StringSet>(", ", m.systemTypes)
-                                % m.maxJobs
-                                % concatStringsSep<StringSet>(", ", m.supportedFeatures)
-                                % concatStringsSep<StringSet>(", ", m.mandatoryFeatures);
+                        for (auto & m : machines) {
+                            machinesFormatted += HintFmt(
+                                "\n([%s], %s, [%s], [%s])",
+                                concatStringsSep<StringSet>(", ", m.systemTypes),
+                                m.maxJobs,
+                                concatStringsSep<StringSet>(", ", m.supportedFeatures),
+                                concatStringsSep<StringSet>(", ", m.mandatoryFeatures)
+                            ).str();
+                        }
+
+                        auto error = HintFmt(
+                            "Failed to find a machine for remote build!\n"
+                            "derivation: %s\n"
+                            "required (system, features): (%s, [%s])\n"
+                            "%s available machines:\n"
+                            "(systems, maxjobs, supportedFeatures, mandatoryFeatures)%s",
+                            drvstr,
+                            neededSystem,
+                            concatStringsSep<StringSet>(", ", requiredFeatures),
+                            machines.size(),
+                            Uncolored(machinesFormatted)
+                       );
 
                         printMsg(couldBuildLocally ? lvlChatty : lvlWarn, error.str());
 

src/libcmd/meson.build

@@ -44,6 +44,7 @@ libcmd = library(
     boehm,
     editline,
     lowdown,
+    nlohmann_json,
   ],
   install : true,
   # FIXME(Qyriad): is this right?
@@ -56,3 +57,17 @@ liblixcmd = declare_dependency(
   include_directories : '.',
   link_with : libcmd,
 )
+
+# FIXME: not using the pkg-config module because it creates way too many deps
+# while meson migration is in progress, and we want to not include boost here
+configure_file(
+  input : 'nix-cmd.pc.in',
+  output : 'nix-cmd.pc',
+  install_dir : libdir / 'pkgconfig',
+  configuration : {
+    'prefix' : prefix,
+    'libdir' : libdir,
+    'includedir' : includedir,
+    'PACKAGE_VERSION' : meson.project_version(),
+  },
+)

src/libexpr/flake/meson.build

@@ -0,0 +1,8 @@
+libexpr_generated_headers += custom_target(
+  command : [ 'bash', '-c', 'echo \'R"__NIX_STR(\' | cat - @INPUT@ && echo \')__NIX_STR"\'' ],
+  input : 'call-flake.nix',
+  output : '@PLAINNAME@.gen.hh',
+  capture : true,
+  install : true,
+  install_dir : includedir / 'nix/flake',
+)

src/libexpr/meson.build

@@ -49,10 +49,20 @@ meson.add_install_script(
   '@0@'.format(includedir),
 )
 
-imported_drv_to_derivation_gen = gen_header.process('imported-drv-to-derivation.nix')
-fetchurl_gen = gen_header.process('fetchurl.nix')
-derivation_gen = gen_header.process('primops/derivation.nix', preserve_path_from : meson.current_source_dir())
-call_flake_gen = gen_header.process('flake/call-flake.nix')
+libexpr_generated_headers = [
+  gen_header.process('primops/derivation.nix', preserve_path_from : meson.current_source_dir()),
+]
+foreach header : [ 'imported-drv-to-derivation.nix', 'fetchurl.nix' ]
+  libexpr_generated_headers += custom_target(
+    command : [ 'bash', '-c', 'echo \'R"__NIX_STR(\' | cat - @INPUT@ && echo \')__NIX_STR"\'' ],
+    input : header,
+    output : '@PLAINNAME@.gen.hh',
+    capture : true,
+    install : true,
+    install_dir : includedir / 'nix',
+  )
+endforeach
+subdir('flake')
 
 libexpr_sources = files(
   'attr-path.cc',
@@ -121,10 +131,7 @@ libexpr = library(
   libexpr_sources,
   parser_tab,
   lexer_tab,
-  imported_drv_to_derivation_gen,
-  fetchurl_gen,
-  derivation_gen,
-  call_flake_gen,
+  libexpr_generated_headers,
   dependencies : [
     liblixutil,
     liblixstore,
@@ -132,6 +139,7 @@ libexpr = library(
     boehm,
     boost,
     toml11,
+    nlohmann_json,
   ],
   # for shared.hh
   include_directories : [
@@ -152,3 +160,17 @@ liblixexpr = declare_dependency(
   include_directories : include_directories('.'),
   link_with : libexpr,
 )
+
+# FIXME: not using the pkg-config module because it creates way too many deps
+# while meson migration is in progress, and we want to not include boost here
+configure_file(
+  input : 'nix-expr.pc.in',
+  output : 'nix-expr.pc',
+  install_dir : libdir / 'pkgconfig',
+  configuration : {
+    'prefix' : prefix,
+    'libdir' : libdir,
+    'includedir' : includedir,
+    'PACKAGE_VERSION' : meson.project_version(),
+  },
+)

src/libexpr/print.cc

@@ -608,7 +608,7 @@ std::ostream & operator<<(std::ostream & output, const ValuePrinter & printer)
 }
 
 template<>
-HintFmt & HintFmt::operator%(const ValuePrinter & value)
+fmt_internal::HintFmt & fmt_internal::HintFmt::operator%(const ValuePrinter & value)
 {
         fmt % value;
         return *this;

src/libexpr/print.hh

@@ -86,6 +86,6 @@ std::ostream & operator<<(std::ostream & output, const ValuePrinter & printer);
  * magenta.
  */
 template<>
-HintFmt & HintFmt::operator%(const ValuePrinter & value);
+fmt_internal::HintFmt & fmt_internal::HintFmt::operator%(const ValuePrinter & value);
 
 }

src/libfetchers/meson.build

@@ -28,6 +28,7 @@ libfetchers = library(
   dependencies : [
     liblixstore,
     liblixutil,
+    nlohmann_json,
   ],
   install : true,
   # FIXME(Qyriad): is this right?

src/libmain/meson.build

@@ -31,3 +31,17 @@ liblixmain = declare_dependency(
   include_directories : include_directories('.'),
   link_with : libmain,
 )
+
+# FIXME: not using the pkg-config module because it creates way too many deps
+# while meson migration is in progress, and we want to not include boost here
+configure_file(
+  input : 'nix-main.pc.in',
+  output : 'nix-main.pc',
+  install_dir : libdir / 'pkgconfig',
+  configuration : {
+    'prefix' : prefix,
+    'libdir' : libdir,
+    'includedir' : includedir,
+    'PACKAGE_VERSION' : meson.project_version(),
+  },
+)

src/libstore/meson.build

@@ -1,5 +1,14 @@
-schema_sql_gen = gen_header.process('schema.sql')
-ca_specific_schema_gen = gen_header.process('ca-specific-schema.sql')
+libstore_generated_headers = []
+foreach header : [ 'schema.sql', 'ca-specific-schema.sql' ]
+  libstore_generated_headers += custom_target(
+    command : [ 'bash', '-c', 'echo \'R"__NIX_STR(\' | cat - @INPUT@ && echo \')__NIX_STR"\'' ],
+    input : header,
+    output : '@PLAINNAME@.gen.hh',
+    capture : true,
+    install : true,
+    install_dir : includedir / 'nix',
+  )
+endforeach
 
 libstore_sources = files(
   'binary-cache-store.cc',
@@ -140,7 +149,7 @@ cpp_str_defines = {
   'NIX_PREFIX':    prefix,
   'NIX_STORE_DIR': store_dir,
   'NIX_DATA_DIR':  datadir,
-  'NIX_STATE_DIR': state_dir,
+  'NIX_STATE_DIR': state_dir / 'nix',
   'NIX_LOG_DIR':   log_dir,
   'NIX_CONF_DIR':  sysconfdir,
   'NIX_BIN_DIR':   bindir,
@@ -157,8 +166,7 @@ endforeach
 
 libstore = library(
   'nixstore',
-  schema_sql_gen,
-  ca_specific_schema_gen,
+  libstore_generated_headers,
   libstore_sources,
   dependencies : [
     libarchive,
@@ -172,6 +180,7 @@ libstore = library(
     aws_sdk,
     aws_s3,
     aws_sdk_transfer,
+    nlohmann_json,
   ],
   cpp_args : cpp_args,
   install : true,
@@ -186,3 +195,17 @@ liblixstore = declare_dependency(
   include_directories : include_directories('.'),
   link_with : libstore,
 )
+
+# FIXME: not using the pkg-config module because it creates way too many deps
+# while meson migration is in progress, and we want to not include boost here
+configure_file(
+  input : 'nix-store.pc.in',
+  output : 'nix-store.pc',
+  install_dir : libdir / 'pkgconfig',
+  configuration : {
+    'prefix' : prefix,
+    'libdir' : libdir,
+    'includedir' : includedir,
+    'PACKAGE_VERSION' : meson.project_version(),
+  },
+)

src/libutil/escape-char.cc

@@ -0,0 +1,22 @@
+#include <boost/io/ios_state.hpp>
+#include <iomanip>
+#include <iostream>
+
+#include "escape-char.hh"
+
+namespace nix {
+
+std::ostream & operator<<(std::ostream & s, MaybeHexEscapedChar c)
+{
+    boost::io::ios_flags_saver _ifs(s);
+
+    if (isprint(c.c)) {
+        s << static_cast<char>(c.c);
+    } else {
+        s << "\\x" << std::hex << std::setfill('0') << std::setw(2)
+          << (static_cast<unsigned int>(c.c) & 0xff);
+    }
+    return s;
+}
+
+} // namespace nix

src/libutil/escape-char.hh

@@ -0,0 +1,22 @@
+#pragma once
+#include <ostream>
+
+namespace nix {
+
+/**
+ * A struct that prints a debug representation of a character, like `\x1f` for
+ * non-printable characters, or the character itself for other characters.
+ *
+ * Note that these are suitable for human readable output, but further care is
+ * necessary to include them in C++ strings to avoid running into adjacent
+ * hex-like characters. (`"puppy\x1bdoggy"` parses as `"puppy" "\x1bd" "oggy"`
+ * and errors because 0x1bd is too big for a `char`.)
+ */
+struct MaybeHexEscapedChar
+{
+    char c;
+};
+
+std::ostream & operator<<(std::ostream & s, MaybeHexEscapedChar c);
+
+} // namespace nix

src/libutil/fmt.hh

@@ -5,43 +5,94 @@
 #include <string>
 #include "ansicolor.hh"
 
-
 namespace nix {
 
-namespace {
 /**
- * A helper for writing `boost::format` expressions.
+ * Values wrapped in this struct are printed in magenta.
  *
- * These are equivalent:
- *
- * ```
- * formatHelper(formatter, a_0, ..., a_n)
- * formatter % a_0 % ... % a_n
- * ```
- *
- * With a single argument, `formatHelper(s)` is a no-op.
+ * 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 F>
-inline void formatHelper(F & f)
-{ }
-
-template<class F, typename T, typename... Args>
-inline void formatHelper(F & f, const T & x, const Args & ... args)
+template<class T>
+struct Magenta
 {
-    // Interpolate one argument and then recurse.
-    formatHelper(f % x, args...);
+    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`.
  */
-void setExceptions(boost::format & 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);
+        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);
+    }
+};
+
 }
 
 /**
@@ -77,52 +128,14 @@ inline std::string fmt(const char * s)
 }
 
 template<typename... Args>
-inline std::string fmt(const std::string & fs, const Args & ... args)
+inline std::string fmt(const std::string & fs, const Args &... args)
 {
     boost::format f(fs);
-    setExceptions(f);
-    formatHelper(f, args...);
+    fmt_internal::setExceptions(f);
+    (f % ... % args);
     return f.str();
 }
 
-/**
- * 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_WARNING << 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;
-}
-
 /**
  * A wrapper around `boost::format` which colors interpolated arguments in
  * magenta by default.
@@ -137,46 +150,28 @@ public:
      * Format the given string literally, without interpolating format
      * placeholders.
      */
-    HintFmt(const std::string & literal)
-        : HintFmt("%s", Uncolored(literal))
-    { }
-
-    static HintFmt fromFormatString(const std::string & format) {
-        return HintFmt(boost::format(format));
-    }
+    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)
+    HintFmt(const std::string & format, const Args &... args)
         : HintFmt(boost::format(format), args...)
-    { }
+    {
+    }
 
-    HintFmt(const HintFmt & hf)
-        : fmt(hf.fmt)
-    { }
+    HintFmt(const HintFmt & hf) : fmt(hf.fmt) {}
 
     template<typename... Args>
-    HintFmt(boost::format && fmt, const Args & ... args)
-        : fmt(std::move(fmt))
+    HintFmt(boost::format && fmt, const Args &... args)
+        : fmt(fmt_internal::HintFmt(std::move(fmt), args...).into_format())
     {
-        setExceptions(fmt);
-        formatHelper(*this, args...);
+        if (this->fmt.remaining_args() != 0) {
+            throw boost::io::too_few_args(
+                this->fmt.bound_args() + this->fmt.fed_args(), this->fmt.expected_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;
     }
 
     std::string str() const

src/libutil/logging.hh

@@ -230,9 +230,7 @@ extern Verbosity verbosity;
 template<typename... Args>
 inline void warn(const std::string & fs, const Args & ... args)
 {
-    boost::format f(fs);
-    formatHelper(f, args...);
-    logger->warn(f.str());
+    logger->warn(HintFmt(fs, args...).str());
 }
 
 #define warnOnce(haveWarned, args...) \

src/libutil/meson.build

@@ -8,6 +8,7 @@ libutil_sources = files(
   'config.cc',
   'english.cc',
   'error.cc',
+  'escape-char.cc',
   'exit.cc',
   'experimental-features.cc',
   'filesystem.cc',
@@ -35,6 +36,7 @@ libutil_headers = files(
   'abstract-setting-to-json.hh',
   'ansicolor.hh',
   'archive.hh',
+  'args/root.hh',
   'args.hh',
   'box_ptr.hh',
   'callback.hh',
@@ -49,6 +51,7 @@ libutil_headers = files(
   'config.hh',
   'english.hh',
   'error.hh',
+  'escape-char.hh',
   'exit.hh',
   'experimental-features.hh',
   'experimental-features-json.hh',
@@ -102,6 +105,7 @@ libutil = library(
     libarchive,
     brotli,
     openssl,
+    nlohmann_json,
   ],
   implicit_include_directories : true,
   install : true,

src/nix/meson.build

@@ -87,6 +87,7 @@ nix = executable(
     liblixfetchers,
     liblixmain,
     boehm,
+    nlohmann_json,
   ],
   install : true,
   # FIXME(Qyriad): is this right?

tests/functional/meson.build

@@ -176,5 +176,8 @@ foreach script : functional_tests_scripts
     env : {
       'MESON_BUILD_ROOT': meson.project_build_root(),
     },
+    # some tests take 15+ seconds even on an otherwise idle machine, on a loaded machine
+    # this can easily drive them to failure. give them more time, 5min rather than 30sec
+    timeout : 300,
   )
 endforeach

tests/functional/repl_characterization/test-session.cc

@@ -3,7 +3,7 @@
 
 #include "test-session.hh"
 #include "util.hh"
-#include "tests/debug-char.hh"
+#include "escape-char.hh"
 
 namespace nix {
 
@@ -60,7 +60,7 @@ std::ostream & operator<<(std::ostream & os, ReplOutputParser::State s)
 void ReplOutputParser::transition(State new_state, char responsible_char, bool wasPrompt)
 {
     if constexpr (DEBUG_REPL_PARSER) {
-        std::cerr << "transition " << new_state << " for " << DebugChar{responsible_char}
+        std::cerr << "transition " << new_state << " for " << MaybeHexEscapedChar{responsible_char}
                   << (wasPrompt ? " [prompt]" : "") << "\n";
     }
     state = new_state;
@@ -118,7 +118,7 @@ bool TestSession::waitForPrompt()
             });
 
             if constexpr (DEBUG_REPL_PARSER) {
-                std::cerr << "raw " << DebugChar{buf[i]} << (wasEaten ? " [eaten]" : "") << "\n";
+                std::cerr << "raw " << MaybeHexEscapedChar{buf[i]} << (wasEaten ? " [eaten]" : "") << "\n";
             }
         }
 

tests/unit/libutil-support/tests/cli-literate-parser.cc

@@ -1,6 +1,6 @@
 #include "cli-literate-parser.hh"
 #include "libexpr/print.hh"
-#include "debug-char.hh"
+#include "escape-char.hh"
 #include "types.hh"
 #include "util.hh"
 #include <ranges>
@@ -77,7 +77,7 @@ CLILiterateParser::CLILiterateParser(std::string prompt, size_t indent)
 void CLILiterateParser::feed(char c)
 {
     if constexpr (DEBUG_PARSER) {
-        std::cout << stateDebug(state_) << " " << DebugChar{c} << "\n";
+        std::cout << stateDebug(state_) << " " << MaybeHexEscapedChar{c} << "\n";
     }
 
     if (c == '\n') {

tests/unit/libutil-support/tests/debug-char.hh

@@ -1,24 +0,0 @@
-///@file
-#include <ostream>
-#include <boost/io/ios_state.hpp>
-
-namespace nix {
-
-struct DebugChar
-{
-    char c;
-};
-
-inline std::ostream & operator<<(std::ostream & s, DebugChar c)
-{
-    boost::io::ios_flags_saver _ifs(s);
-
-    if (isprint(c.c)) {
-        s << static_cast<char>(c.c);
-    } else {
-        s << std::hex << "0x" << (static_cast<unsigned int>(c.c) & 0xff);
-    }
-    return s;
-}
-
-}

tests/unit/libutil-support/tests/terminal-code-eater.cc

@@ -1,5 +1,5 @@
 #include "terminal-code-eater.hh"
-#include "debug-char.hh"
+#include "escape-char.hh"
 #include <assert.h>
 #include <cstdint>
 #include <iostream>
@@ -14,7 +14,7 @@ void TerminalCodeEater::feed(char c, std::function<void(char)> on_char)
     auto isIntermediateChar = [](char v) -> bool { return v >= 0x20 && v <= 0x2f; };
     auto isFinalChar = [](char v) -> bool { return v >= 0x40 && v <= 0x7e; };
     if constexpr (DEBUG_EATER) {
-        std::cerr << "eater" << DebugChar{c} << "\n";
+        std::cerr << "eater" << MaybeHexEscapedChar{c} << "\n";
     }
 
     switch (state) {
@@ -28,7 +28,7 @@ void TerminalCodeEater::feed(char c, std::function<void(char)> on_char)
             return;
         }
         if constexpr (DEBUG_EATER) {
-            std::cerr << "eater uneat" << DebugChar{c} << "\n";
+            std::cerr << "eater uneat" << MaybeHexEscapedChar{c} << "\n";
         }
         on_char(c);
         break;

tests/unit/libutil/fmt.cc

@@ -0,0 +1,23 @@
+#include "fmt.hh"
+#include "ansicolor.hh"
+
+#include <gtest/gtest.h>
+
+namespace nix {
+
+TEST(HintFmt, arg_count)
+{
+    // Single arg is treated as a literal string.
+    ASSERT_EQ(HintFmt("%s").str(), "%s");
+
+    // Other strings format as expected:
+    ASSERT_EQ(HintFmt("%s", 1).str(), ANSI_MAGENTA "1" ANSI_NORMAL);
+    ASSERT_EQ(HintFmt("%1%", "hello").str(), ANSI_MAGENTA "hello" ANSI_NORMAL);
+
+    // Argument counts are detected at construction.
+    ASSERT_THROW(HintFmt("%s %s", 1), boost::io::too_few_args);
+
+    ASSERT_THROW(HintFmt("%s", 1, 2), boost::io::too_many_args);
+}
+
+}

tests/unit/meson.build

@@ -63,6 +63,7 @@ libutil_tester = executable(
     liblixutil,
     liblixexpr,
     liblixutil_test_support,
+    nlohmann_json,
   ],
 )
 
@@ -127,6 +128,7 @@ libstore_tester = executable(
     liblixutil,
     rapidcheck,
     gtest,
+    nlohmann_json,
   ],
 )
 
@@ -191,6 +193,7 @@ libexpr_tester = executable(
     rapidcheck,
     boehm,
     gtest,
+    nlohmann_json,
   ],
 )