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primops: Move functions to primops/system.cc

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Moved builtins: exec, getEnv

Change-Id: Ie1b64e4ea8c71f5f64a80ab890a467f5194b884c
This commit is contained in:
Tom Hubrecht 2024-05-30 10:06:52 +02:00
parent 2279c39bea
commit c3ffa21778
3 changed files with 102 additions and 62 deletions
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1
src/libexpr/meson.build
View file

@ -101,6 +101,7 @@ libexpr_sources = files(
'primops/list.cc',
'primops/path.cc',
'primops/string.cc',
'primops/system.cc',
'primops/types.cc',
'value/context.cc',
)

62
src/libexpr/primops.cc
View file

@ -118,45 +118,6 @@ StringMap EvalState::realiseContext(const NixStringContext & context)
/* Execute a program and parse its output */
void prim_exec(EvalState & state, const PosIdx pos, Value * * args, Value & v)
{
state.forceList(*args[0], pos, "while evaluating the first argument passed to builtins.exec");
auto elems = args[0]->listElems();
auto count = args[0]->listSize();
if (count == 0)
state.error<EvalError>("at least one argument to 'exec' required").atPos(pos).debugThrow();
NixStringContext context;
auto program = state.coerceToString(pos, *elems[0], context,
"while evaluating the first element of the argument passed to builtins.exec",
false, false).toOwned();
Strings commandArgs;
for (unsigned int i = 1; i < args[0]->listSize(); ++i) {
commandArgs.push_back(
state.coerceToString(pos, *elems[i], context,
"while evaluating an element of the argument passed to builtins.exec",
false, false).toOwned());
}
try {
auto _ = state.realiseContext(context); // FIXME: Handle CA derivations
} catch (InvalidPathError & e) {
state.error<EvalError>("cannot execute '%1%', since path '%2%' is not valid", program, e.path).atPos(pos).debugThrow();
}
auto output = runProgram(program, true, commandArgs);
Expr * parsed;
try {
parsed = state.parseExprFromString(std::move(output), state.rootPath(CanonPath::root));
} catch (Error & e) {
e.addTrace(state.positions[pos], "while parsing the output from '%1%'", program);
throw;
}
try {
state.eval(parsed, v);
} catch (Error & e) {
e.addTrace(state.positions[pos], "while evaluating the output from '%1%'", program);
throw;
}
}
@ -200,29 +161,6 @@ static RegisterPrimOp primop_addErrorContext(PrimOp {
* else => {success=false; value=false;} */
/* Return an environment variable. Use with care. */
static void prim_getEnv(EvalState & state, const PosIdx pos, Value * * args, Value & v)
{
std::string name(state.forceStringNoCtx(*args[0], pos, "while evaluating the first argument passed to builtins.getEnv"));
v.mkString(evalSettings.restrictEval || evalSettings.pureEval ? "" : getEnv(name).value_or(""));
}
static RegisterPrimOp primop_getEnv({
.name = "__getEnv",
.args = {"s"},
.doc = R"(
`getEnv` returns the value of the environment variable *s*, or an
empty string if the variable doesn’t exist. This function should be
used with care, as it can introduce all sorts of nasty environment
dependencies in your Nix expression.
`getEnv` is used in Nix Packages to locate the file
`~/.nixpkgs/config.nix`, which contains user-local settings for Nix
Packages. (That is, it does a `getEnv "HOME"` to locate the user’s
home directory.)
)",
.fun = prim_getEnv,
});
/* Evaluate the first argument, then return the second argument. */

101
src/libexpr/primops/system.cc Normal file
View file

@ -0,0 +1,101 @@
#include "eval-settings.hh"
#include "primops.hh"
namespace nix {
/**
* builtins.exec
*/
void prim_exec(EvalState & state, const PosIdx pos, Value ** args, Value & v)
{
state.forceList(*args[0], pos, "while evaluating the first argument passed to builtins.exec");
auto elems = args[0]->listElems();
auto count = args[0]->listSize();
if (count == 0) {
state.error<EvalError>("at least one argument to 'exec' required").atPos(pos).debugThrow();
}
NixStringContext context;
auto program =
state
.coerceToString(
pos,
*elems[0],
context,
"while evaluating the first element of the argument passed to builtins.exec",
false,
false
)
.toOwned();
Strings commandArgs;
for (unsigned int i = 1; i < args[0]->listSize(); ++i) {
commandArgs.push_back(
state
.coerceToString(
pos,
*elems[i],
context,
"while evaluating an element of the argument passed to builtins.exec",
false,
false
)
.toOwned()
);
}
try {
auto _ = state.realiseContext(context); // FIXME: Handle CA derivations
} catch (InvalidPathError & e) {
state
.error<EvalError>(
"cannot execute '%1%', since path '%2%' is not valid", program, e.path
)
.atPos(pos)
.debugThrow();
}
auto output = runProgram(program, true, commandArgs);
Expr * parsed;
try {
parsed = state.parseExprFromString(std::move(output), state.rootPath(CanonPath::root));
} catch (Error & e) {
e.addTrace(state.positions[pos], "while parsing the output from '%1%'", program);
throw;
}
try {
state.eval(parsed, v);
} catch (Error & e) {
e.addTrace(state.positions[pos], "while evaluating the output from '%1%'", program);
throw;
}
}
/**
* builtins.getEnv
*/
static void prim_getEnv(EvalState & state, const PosIdx pos, Value ** args, Value & v)
{
std::string name(state.forceStringNoCtx(
*args[0], pos, "while evaluating the first argument passed to builtins.getEnv"
));
v.mkString(evalSettings.restrictEval || evalSettings.pureEval ? "" : getEnv(name).value_or(""));
}
static RegisterPrimOp primop_getEnv({
.name = "__getEnv",
.args = {"s"},
.doc = R"(
`getEnv` returns the value of the environment variable *s*, or an
empty string if the variable doesn’t exist. This function should be
used with care, as it can introduce all sorts of nasty environment
dependencies in your Nix expression.
`getEnv` is used in Nix Packages to locate the file
`~/.nixpkgs/config.nix`, which contains user-local settings for Nix
Packages. (That is, it does a `getEnv "HOME"` to locate the user’s
home directory.)
)",
.fun = prim_getEnv,
});
}