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#include "command.hh"
#include "common-args.hh"
#include "shared.hh"
#include "store-api.hh"
#include "eval.hh"
#include "json.hh"
#include "value-to-json.hh"
#include "progress-bar.hh"
using namespace nix;
struct CmdEval : MixJSON, InstallableCommand
{
bool raw = false;
std::optional<std::string> apply;
CmdEval()
{
mkFlag(0, "raw", "print strings unquoted", &raw);
addFlag({
.longName = "apply",
.description = "apply a function to each argument",
.labels = {"expr"},
.handler = {&apply},
});
}
std::string description() override
{
return "evaluate a Nix expression";
}
Examples examples() override
{
return {
{
"To evaluate a Nix expression given on the command line:",
"nix eval --expr '1 + 2'"
},
{
"To evaluate a Nix expression from a file or URI:",
"nix eval -f ./my-nixpkgs hello.name"
},
{
"To get the current version of Nixpkgs:",
"nix eval --raw nixpkgs#lib.version"
},
{
"To print the store path of the Hello package:",
"nix eval --raw nixpkgs#hello"
},
{
"To get a list of checks in the 'nix' flake:",
"nix eval nix#checks.x86_64-linux --apply builtins.attrNames"
},
};
}
Category category() override { return catSecondary; }
void run(ref<Store> store) override
{
if (raw && json)
throw UsageError("--raw and --json are mutually exclusive");
auto state = getEvalState();
auto v = installable->toValue(*state).first;
PathSet context;
if (apply) {
auto vApply = state->allocValue();
state->eval(state->parseExprFromString(*apply, absPath(".")), *vApply);
auto vRes = state->allocValue();
state->callFunction(*vApply, *v, *vRes, noPos);
v = vRes;
}
if (raw) {
stopProgressBar();
std::cout << state->coerceToString(noPos, *v, context);
} else if (json) {
JSONPlaceholder jsonOut(std::cout);
printValueAsJSON(*state, true, *v, jsonOut, context);
} else {
state->forceValueDeep(*v);
logger->cout("%s", *v);
}
}
};
static auto rCmdEval = registerCommand<CmdEval>("eval");
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