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Args::Flag: Add required attribute #14087

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Merged
edolstra merged 1 commit into from
Oct 8, 2025
Merged

Args::Flag: Add required attribute #14087

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22 changes: 21 additions & 1 deletion src/libutil/args.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -318,6 +318,7 @@ void RootArgs::parseCmdline(const Strings & _cmdline, bool allowShebang)
} catch (SystemError &) {
}
}

for (auto pos = cmdline.begin(); pos != cmdline.end();) {

auto arg = *pos;
Expand Down Expand Up @@ -354,6 +355,9 @@ void RootArgs::parseCmdline(const Strings & _cmdline, bool allowShebang)

processArgs(pendingArgs, true);

if (!completions)
checkArgs();

initialFlagsProcessed();

/* Now that we are done parsing, make sure that any experimental
Expand Down Expand Up @@ -384,7 +388,7 @@ bool Args::processFlag(Strings::iterator & pos, Strings::iterator end)

auto & rootArgs = getRoot();

auto process = [&](const std::string & name, const Flag & flag) -> bool {
auto process = [&](const std::string & name, Flag & flag) -> bool {
++pos;

if (auto & f = flag.experimentalFeature)
Expand Down Expand Up @@ -413,6 +417,7 @@ bool Args::processFlag(Strings::iterator & pos, Strings::iterator end)
}
if (!anyCompleted)
flag.handler.fun(std::move(args));
flag.timesUsed++;
return true;
};

Expand Down Expand Up @@ -504,6 +509,14 @@ bool Args::processArgs(const Strings & args, bool finish)
return res;
}

void Args::checkArgs()
{
for (auto & [name, flag] : longFlags) {
if (flag->required && flag->timesUsed == 0)
throw UsageError("required argument '--%s' is missing", name);
Comment on lines +515 to +516
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@Ericson2314 Ericson2314 Sep 26, 2025

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Can we list multiple such flags?

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@edolstra edolstra Sep 29, 2025

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Yes, there can be multiple required flags.

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@Ericson2314 Ericson2314 Sep 30, 2025

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Yeah I mean collect them all and throw error with all of them

}
}

nlohmann::json Args::toJSON()
{
auto flags = nlohmann::json::object();
Expand Down Expand Up @@ -643,6 +656,13 @@ bool MultiCommand::processArgs(const Strings & args, bool finish)
return Args::processArgs(args, finish);
}

void MultiCommand::checkArgs()
{
Args::checkArgs();
if (command)
command->second->checkArgs();
}

nlohmann::json MultiCommand::toJSON()
{
auto cmds = nlohmann::json::object();
Expand Down
8 changes: 8 additions & 0 deletions src/libutil/include/nix/util/args.hh
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Expand Up @@ -202,8 +202,12 @@ public:
Strings labels;
Handler handler;
CompleterClosure completer;
bool required = false;

std::optional<ExperimentalFeature> experimentalFeature;

// FIXME: this should be private, but that breaks designated initializers.
size_t timesUsed = 0;
Comment on lines +208 to +210
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@xokdvium xokdvium Sep 26, 2025

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It's really ugly that Flag becomes mutable. Can we avoid this by storing the use-count separately? I would hope that Flag stays an immutable description with a callback. Can't we instead track if the argument has been specified multiple times in the Handler?

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@Ericson2314 Ericson2314 Sep 30, 2025

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Yes I would prefer that too, thanks for catching @xokdvium

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@edolstra edolstra Sep 30, 2025

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I don't think it's a problem since Args owns the Flags anyway (i.e. it was already mutable).

};

protected:
Expand Down Expand Up @@ -283,6 +287,8 @@ protected:

StringSet hiddenCategories;

virtual void checkArgs();

/**
* Called after all command line flags before the first non-flag
* argument (if any) have been processed.
Expand Down Expand Up @@ -428,6 +434,8 @@ public:
protected:
std::string commandName = "";
bool aliasUsed = false;

void checkArgs() override;
};

Strings argvToStrings(int argc, char ** argv);
Expand Down
8 changes: 3 additions & 5 deletions src/nix/sigs.cc
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Expand Up @@ -144,7 +144,7 @@ static auto rCmdSign = registerCommand2<CmdSign>({"store", "sign"});

struct CmdKeyGenerateSecret : Command
{
std::optional<std::string> keyName;
std::string keyName;

CmdKeyGenerateSecret()
{
Expand All @@ -153,6 +153,7 @@ struct CmdKeyGenerateSecret : Command
.description = "Identifier of the key (e.g. `cache.example.org-1`).",
.labels = {"name"},
.handler = {&keyName},
.required = true,
});
}

Expand All @@ -170,11 +171,8 @@ struct CmdKeyGenerateSecret : Command

void run() override
{
if (!keyName)
throw UsageError("required argument '--key-name' is missing");

logger->stop();
writeFull(getStandardOutput(), SecretKey::generate(*keyName).to_string());
writeFull(getStandardOutput(), SecretKey::generate(keyName).to_string());
}
};

Expand Down
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