forked from lix-project/lix
75 lines
2.1 KiB
C++
75 lines
2.1 KiB
C++
#include "attr-path.hh"
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#include "nixexpr-ast.hh"
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bool isAttrs(EvalState & state, Expr e, ATermMap & attrs)
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{
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e = evalExpr(state, e);
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ATermList dummy;
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if (!matchAttrs(e, dummy)) return false;
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queryAllAttrs(e, attrs, false);
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return true;
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}
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Expr findAlongAttrPath(EvalState & state, const string & attrPath, Expr e)
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{
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Strings tokens = tokenizeString(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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string curPath;
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for (Strings::iterator i = tokens.begin(); i != tokens.end(); ++i) {
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if (!curPath.empty()) curPath += ".";
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curPath += *i;
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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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int attrIndex = -1;
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if (string2Int(attr, attrIndex)) apType = apIndex;
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/* Evaluate the expression. */
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e = evalExpr(state, autoCallFunction(evalExpr(state, e)));
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/* It should evaluate to either an attribute set or an
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expression, according to what is specified in the
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attrPath. */
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if (apType == apAttr) {
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ATermMap attrs(128);
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if (!isAttrs(state, e, attrs))
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throw TypeError(
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format("the expression selected by the selection path `%1%' should be an attribute set but is %2%")
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% curPath % showType(e));
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e = attrs.get(toATerm(attr));
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if (!e)
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throw Error(format("attribute `%1%' in selection path `%2%' not found") % attr % curPath);
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}
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else if (apType == apIndex) {
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ATermList es;
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if (!matchList(e, es))
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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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% curPath % showType(e));
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e = ATelementAt(es, attrIndex);
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if (!e)
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throw Error(format("list index %1% in selection path `%2%' not found") % attrIndex % curPath);
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}
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}
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return e;
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}
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