* Allow string concatenations involving derivations, e.g.,
configureFlags = "--with-freetype2-library=" + freetype + "/lib";
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@ -149,6 +149,103 @@ ATermList evalList(EvalState & state, Expr e)
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}
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/* String concatenation and context nodes: in order to allow users to
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write things like
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"--with-freetype2-library=" + freetype + "/lib"
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where `freetype' is a derivation, we automatically coerce
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derivations into their output path (e.g.,
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/nix/store/hashcode-freetype) in concatenations. However, if we do
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this naively, we could introduce an undeclared dependency: when the
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string is used in another derivation, that derivation would not
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have an explicitly dependency on `freetype' in its inputDrvs
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field. Thus `freetype' would not necessarily be built.
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To prevent this, we wrap the string resulting from the
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concatenation in a *context node*, like this:
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Context([freetype],
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Str("--with-freetype2-library=/nix/store/hashcode-freetype/lib"))
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Thus the context is the list of all derivations used in the
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computation of a value. These contexts are propagated through
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further concatenations. In processBinding() in primops.cc, context
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nodes are unwrapped and added to inputDrvs.
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!!! Should the ordering of the context list have a canonical form?
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!!! Contexts are not currently recognised in most places in the
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evaluator. */
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/* Coerce a value to a string, keeping track of contexts. */
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string coerceToStringWithContext(EvalState & state,
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ATermList & context, Expr e, bool & isPath)
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{
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isPath = false;
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e = evalExpr(state, e);
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ATermList es;
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ATerm e2;
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if (matchContext(e, es, e2)) {
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e = e2;
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context = ATconcat(es, context);
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}
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ATerm s;
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if (matchStr(e, s) || matchUri(e, s))
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return aterm2String(s);
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if (matchPath(e, s)) {
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isPath = true;
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return aterm2String(s);
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}
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if (matchAttrs(e, es)) {
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ATermMap attrs;
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queryAllAttrs(e, attrs, false);
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Expr a = attrs.get("type");
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if (a && evalString(state, a) == "derivation") {
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a = attrs.get("outPath");
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if (!a) throw Error("output path missing from derivation");
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context = ATinsert(context, e);
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return evalPath(state, a);
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}
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}
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throw Error("cannot coerce value to string");
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}
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/* Wrap an expression in a context if the context is not empty. */
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Expr wrapInContext(ATermList context, Expr e)
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{
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return context == ATempty ? e : makeContext(context, e);
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}
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static ATerm concatStrings(EvalState & state, const ATermVector & args)
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{
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ATermList context = ATempty;
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ostringstream s;
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bool isPath;
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for (ATermVector::const_iterator i = args.begin(); i != args.end(); ++i) {
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bool isPath2;
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s << coerceToStringWithContext(state, context, *i, isPath2);
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if (i == args.begin()) isPath = isPath2;
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}
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Expr result = isPath
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? makePath(toATerm(canonPath(s.str())))
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: makeStr(toATerm(s.str()));
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return wrapInContext(context, result);
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}
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Expr evalExpr2(EvalState & state, Expr e)
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{
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Expr e1, e2, e3, e4;
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@ -167,7 +264,8 @@ Expr evalExpr2(EvalState & state, Expr e)
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sym == symFunction1 ||
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sym == symAttrs ||
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sym == symList ||
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sym == symPrimOp)
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sym == symPrimOp ||
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sym == symContext)
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return e;
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/* The `Closed' constructor is just a way to prevent substitutions
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@ -338,16 +436,10 @@ Expr evalExpr2(EvalState & state, Expr e)
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/* String or path concatenation. */
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if (matchOpPlus(e, e1, e2)) {
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e1 = evalExpr(state, e1);
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e2 = evalExpr(state, e2);
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ATerm s1, s2;
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if (matchStr(e1, s1) && matchStr(e2, s2))
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return makeStr(toATerm(
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(string) aterm2String(s1) + (string) aterm2String(s2)));
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else if (matchPath(e1, s1) && matchPath(e2, s2))
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return makePath(toATerm(canonPath(
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(string) aterm2String(s1) + "/" + (string) aterm2String(s2))));
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else throw Error("wrong argument types in `+' operator");
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ATermVector args;
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args.push_back(e1);
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args.push_back(e2);
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return concatStrings(state, args);
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}
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/* List concatenation. */
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@ -59,6 +59,11 @@ bool evalBool(EvalState & state, Expr e);
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ATermList evalList(EvalState & state, Expr e);
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ATerm coerceToString(Expr e);
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/* Contexts. */
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string coerceToStringWithContext(EvalState & state,
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ATermList & context, Expr e, bool & isPath);
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Expr wrapInContext(ATermList context, Expr e);
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/* Print statistics. */
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void printEvalStats(EvalState & state);
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@ -45,6 +45,10 @@ MetaInfo DrvInfo::queryMetaInfo(EvalState & state) const
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}
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/* Cache for already evaluated derivations. Usually putting ATerms in
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a STL container is unsafe (they're not scanning for GC roots), but
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here it doesn't matter; everything in this set is reachable from
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the stack as well. */
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typedef set<Expr> Exprs;
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@ -35,6 +35,7 @@ Closed | Expr | Expr |
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Rec | ATermList ATermList | Expr |
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Bool | ATerm | Expr |
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Null | | Expr |
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Context | ATermList Expr | Expr |
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Bind | string Expr Pos | ATerm |
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Bind | string Expr | ATerm | Bind2
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@ -109,6 +109,14 @@ static void processBinding(EvalState & state, Expr e, Derivation & drv,
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int n;
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Expr e1, e2;
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if (matchContext(e, es, e2)) {
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e = e2;
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for (ATermIterator i(es); i; ++i) {
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Strings dummy;
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processBinding(state, *i, drv, dummy);
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}
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}
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if (matchStr(e, s)) ss.push_back(aterm2String(s));
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else if (matchUri(e, s)) ss.push_back(aterm2String(s));
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else if (e == eTrue) ss.push_back("1");
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@ -408,9 +416,10 @@ ATerm coerceToString(Expr e)
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/* Convert the argument (which can be a path or a uri) to a string. */
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static Expr primToString(EvalState & state, const ATermVector & args)
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{
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ATerm s = coerceToString(evalExpr(state, args[0]));
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if (!s) throw Error("cannot coerce value to string");
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return makeStr(s);
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ATermList context = ATempty;
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bool dummy;
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string s = coerceToStringWithContext(state, context, args[0], dummy);
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return wrapInContext(context, makeStr(toATerm(s)));
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}
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@ -18,8 +18,9 @@ let {
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name = "dependencies";
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system = "@system@";
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builder = "@shell@";
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args = ["-e" "-x" ./dependencies.builder0.sh];
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inherit input1 input2;
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args = ["-e" "-x" (./dependencies.builder0.sh + "/FOOBAR/../.")];
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input1 = input1 + "/.";
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inherit input2;
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};
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}
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@ -1 +1 @@
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Str("foobar/a/b/c/d")
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Str("foobar/a/b/c/d/foo/xyzzy/foo.txt/../foo/x/y")
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@ -1 +1 @@
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"foo" + "bar" + toString (/a/b + /c/d)
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"foo" + "bar" + toString (/a/b + /c/d) + (/foo/bar + "/../xyzzy/." + "/foo.txt") + ("/../foo" + /x/y)
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