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#include "attr-path.hh"
#include "util.hh"
namespace nix {
// !!! Shouldn't we return a pointer to a Value?
void findAlongAttrPath(EvalState & state, const string & attrPath,
Bindings & autoArgs, Expr * e, Value & v)
{
Strings tokens = tokenizeString(attrPath, ".");
Error attrError =
Error(format("attribute selection path `%1%' does not match expression") % attrPath);
string curPath;
state.mkThunk_(v, e);
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;
int attrIndex = -1;
if (string2Int(attr, attrIndex)) apType = apIndex;
/* Evaluate the expression. */
Value vTmp;
state.autoCallFunction(autoArgs, v, vTmp);
v = vTmp;
state.forceValue(v);
/* It should evaluate to either an attribute 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 an attribute 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];
}
}
}
}
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