forked from lix-project/lix
* In the ‘?’ operator, allow attribute paths. For instance, you can
write ‘attrs ? a.b’ to test whether ‘attrs’ has an attribute ‘a’ containing an attribute ‘b’. This is more convenient than ‘attrs ? a && attrs.a ? b’. Slight change in the semantics: it's no longer an error if the left-hand side of ‘?’ is not an attribute set. In that case it just returns false. So, ‘null ? foo’ no longer throws an error.
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34f4b91820
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5637037802
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@ -656,9 +656,25 @@ void ExprSelect::eval(EvalState & state, Env & env, Value & v)
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void ExprOpHasAttr::eval(EvalState & state, Env & env, Value & v)
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{
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Value vAttrs;
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state.evalAttrs(env, e, vAttrs);
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mkBool(v, vAttrs.attrs->find(name) != vAttrs.attrs->end());
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Value vTmp;
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Value * vAttrs = &vTmp;
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state.eval(env, e, vTmp);
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foreach (AttrPath::const_iterator, i, attrPath) {
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state.forceValue(*vAttrs);
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Bindings::iterator j;
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if (vAttrs->type != tAttrs ||
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(j = vAttrs->attrs->find(*i)) == vAttrs->attrs->end())
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{
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mkBool(v, false);
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return;
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} else {
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vAttrs = j->value;
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}
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}
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mkBool(v, true);
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}
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@ -48,7 +48,7 @@ void ExprSelect::show(std::ostream & str)
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void ExprOpHasAttr::show(std::ostream & str)
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{
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str << "(" << *e << ") ? " << name;
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str << "(" << *e << ") ? " << showAttrPath(attrPath);
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}
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void ExprAttrs::show(std::ostream & str)
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@ -140,6 +140,17 @@ std::ostream & operator << (std::ostream & str, const Pos & pos)
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}
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string showAttrPath(const AttrPath & attrPath)
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{
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string s;
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foreach (AttrPath::const_iterator, i, attrPath) {
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if (!s.empty()) s += '.';
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s += *i;
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}
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return s;
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}
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Pos noPos;
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@ -40,6 +40,12 @@ struct EvalState;
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struct StaticEnv;
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/* An attribute path is a sequence of attribute names. */
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typedef vector<Symbol> AttrPath;
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string showAttrPath(const AttrPath & attrPath);
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/* Abstract syntax of Nix expressions. */
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struct Expr
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@ -124,8 +130,8 @@ struct ExprSelect : Expr
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struct ExprOpHasAttr : Expr
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{
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Expr * e;
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Symbol name;
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ExprOpHasAttr(Expr * e, const Symbol & name) : e(e), name(name) { };
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AttrPath attrPath;
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ExprOpHasAttr(Expr * e, const AttrPath & attrPath) : e(e), attrPath(attrPath) { };
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COMMON_METHODS
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};
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@ -61,18 +61,7 @@ using namespace nix;
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namespace nix {
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static string showAttrPath(const vector<Symbol> & attrPath)
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{
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string s;
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foreach (vector<Symbol>::const_iterator, i, attrPath) {
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if (!s.empty()) s += '.';
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s += *i;
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}
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return s;
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}
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static void dupAttr(const vector<Symbol> & attrPath, const Pos & pos, const Pos & prevPos)
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static void dupAttr(const AttrPath & attrPath, const Pos & pos, const Pos & prevPos)
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{
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throw ParseError(format("attribute `%1%' at %2% already defined at %3%")
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% showAttrPath(attrPath) % pos % prevPos);
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@ -81,17 +70,17 @@ static void dupAttr(const vector<Symbol> & attrPath, const Pos & pos, const Pos
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static void dupAttr(Symbol attr, const Pos & pos, const Pos & prevPos)
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{
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vector<Symbol> attrPath; attrPath.push_back(attr);
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AttrPath attrPath; attrPath.push_back(attr);
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throw ParseError(format("attribute `%1%' at %2% already defined at %3%")
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% showAttrPath(attrPath) % pos % prevPos);
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}
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static void addAttr(ExprAttrs * attrs, const vector<Symbol> & attrPath,
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static void addAttr(ExprAttrs * attrs, AttrPath & attrPath,
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Expr * e, const Pos & pos)
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{
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unsigned int n = 0;
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foreach (vector<Symbol>::const_iterator, i, attrPath) {
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foreach (AttrPath::const_iterator, i, attrPath) {
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n++;
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ExprAttrs::AttrDefs::iterator j = attrs->attrs.find(*i);
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if (j != attrs->attrs.end()) {
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@ -238,6 +227,7 @@ void yyerror(YYLTYPE * loc, yyscan_t scanner, ParseData * data, const char * err
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%}
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%union {
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// !!! We're probably leaking stuff here.
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nix::Expr * e;
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nix::ExprList * list;
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nix::ExprAttrs * attrs;
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@ -317,7 +307,7 @@ expr_op
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| expr_op OR expr_op { $$ = new ExprOpOr($1, $3); }
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| expr_op IMPL expr_op { $$ = new ExprOpImpl($1, $3); }
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| expr_op UPDATE expr_op { $$ = new ExprOpUpdate($1, $3); }
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| expr_op '?' ID { $$ = new ExprOpHasAttr($1, data->symbols.create($3)); }
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| expr_op '?' attrpath { $$ = new ExprOpHasAttr($1, *$3); }
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| expr_op '+' expr_op
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{ vector<Expr *> * l = new vector<Expr *>;
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l->push_back($1);
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@ -382,7 +372,7 @@ binds
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: binds attrpath '=' expr ';' { $$ = $1; addAttr($$, *$2, $4, makeCurPos(@2, data)); }
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| binds INHERIT ids ';'
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{ $$ = $1;
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foreach (vector<Symbol>::iterator, i, *$3) {
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foreach (AttrPath::iterator, i, *$3) {
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if ($$->attrs.find(*i) != $$->attrs.end())
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dupAttr(*i, makeCurPos(@3, data), $$->attrs[*i].pos);
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Pos pos = makeCurPos(@3, data);
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@ -392,7 +382,7 @@ binds
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| binds INHERIT '(' expr ')' ids ';'
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{ $$ = $1;
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/* !!! Should ensure sharing of the expression in $4. */
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foreach (vector<Symbol>::iterator, i, *$6) {
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foreach (AttrPath::iterator, i, *$6) {
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if ($$->attrs.find(*i) != $$->attrs.end())
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dupAttr(*i, makeCurPos(@6, data), $$->attrs[*i].pos);
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$$->attrs[*i] = ExprAttrs::AttrDef(new ExprSelect($4, *i), makeCurPos(@6, data));
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