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#include "attr-path.hh"
#include "eval-inline.hh"
#include "util.hh"
namespace nix {
Value * findAlongAttrPath(EvalState & state, const string & attrPath,
Bindings & autoArgs, Value & vIn)
{
Strings tokens = tokenizeString<Strings>(attrPath, ".");
Error attrError =
Error(format("attribute selection path `%1%' does not match expression") % attrPath);
string curPath;
Value * v = &vIn;
foreach (Strings::iterator, i, tokens) {
if (!curPath.empty()) curPath += ".";
curPath += *i;
/* Is *i an index (integer) or a normal attribute name? */
enum { apAttr, apIndex } apType = apAttr;
string attr = *i;
unsigned int attrIndex;
if (string2Int(attr, attrIndex)) apType = apIndex;
/* Evaluate the expression. */
Value * vNew = state.allocValue();
state.autoCallFunction(autoArgs, *v, *vNew);
v = vNew;
state.forceValue(*v);
/* It should evaluate to either a set or an expression,
according to what is specified in the attrPath. */
if (apType == apAttr) {
if (v->type != tAttrs)
throw TypeError(
format("the expression selected by the selection path `%1%' should be a set but is %2%")
% curPath % showType(*v));
Bindings::iterator a = v->attrs->find(state.symbols.create(attr));
if (a == v->attrs->end())
throw Error(format("attribute `%1%' in selection path `%2%' not found") % attr % curPath);
v = &*a->value;
}
else if (apType == apIndex) {
if (v->type != tList)
throw TypeError(
format("the expression selected by the selection path `%1%' should be a list but is %2%")
% curPath % showType(*v));
if (attrIndex >= v->list.length)
throw Error(format("list index %1% in selection path `%2%' is out of range") % attrIndex % curPath);
v = v->list.elems[attrIndex];
}
}
return v;
}
}
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