forked from lix-project/lix
90b5e69284
This is requires if you have attribute names with dots in them. So you can now say: $ nix-instantiate '<nixos>' -A 'config.systemd.units."postgresql.service".text' --eval-only Fixes #151.
98 lines
2.7 KiB
C++
98 lines
2.7 KiB
C++
#include "attr-path.hh"
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#include "eval-inline.hh"
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#include "util.hh"
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namespace nix {
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static Strings parseAttrPath(const string & s)
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{
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Strings res;
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string cur;
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string::const_iterator i = s.begin();
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while (i != s.end()) {
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if (*i == '.') {
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res.push_back(cur);
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cur.clear();
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} else if (*i == '"') {
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++i;
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while (1) {
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if (i == s.end())
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throw Error(format("missing closing quote in selection path `%1%'") % s);
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if (*i == '"') break;
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cur.push_back(*i++);
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}
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} else
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cur.push_back(*i);
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++i;
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}
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if (!cur.empty()) res.push_back(cur);
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return res;
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}
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Value * findAlongAttrPath(EvalState & state, const string & attrPath,
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Bindings & autoArgs, Value & vIn)
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{
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Strings tokens = parseAttrPath(attrPath);
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Error attrError =
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Error(format("attribute selection path `%1%' does not match expression") % attrPath);
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Value * v = &vIn;
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foreach (Strings::iterator, i, tokens) {
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/* Is *i an index (integer) or a normal attribute name? */
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enum { apAttr, apIndex } apType = apAttr;
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string attr = *i;
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unsigned int attrIndex;
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if (string2Int(attr, attrIndex)) apType = apIndex;
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/* Evaluate the expression. */
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Value * vNew = state.allocValue();
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state.autoCallFunction(autoArgs, *v, *vNew);
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v = vNew;
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state.forceValue(*v);
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/* It should evaluate to either a set or an expression,
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according to what is specified in the attrPath. */
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if (apType == apAttr) {
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if (v->type != tAttrs)
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throw TypeError(
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format("the expression selected by the selection path `%1%' should be a set but is %2%")
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% attrPath % showType(*v));
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if (attr.empty())
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throw Error(format("empty attribute name in selection path `%1%'") % attrPath);
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Bindings::iterator a = v->attrs->find(state.symbols.create(attr));
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if (a == v->attrs->end())
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throw Error(format("attribute `%1%' in selection path `%2%' not found") % attr % attrPath);
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v = &*a->value;
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}
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else if (apType == apIndex) {
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if (v->type != tList)
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throw TypeError(
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format("the expression selected by the selection path `%1%' should be a list but is %2%")
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% attrPath % showType(*v));
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if (attrIndex >= v->list.length)
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throw Error(format("list index %1% in selection path `%2%' is out of range") % attrIndex % attrPath);
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v = v->list.elems[attrIndex];
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}
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}
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return v;
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}
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}
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