From b2235d81d1b3733a93fdd1397a62d0f49409dcb0 Mon Sep 17 00:00:00 2001 From: Eelco Dolstra Date: Sat, 15 May 2010 08:10:12 +0000 Subject: * Restore the __overrides feature that was lost somewhere in the fast-eval branch. --- src/libexpr/eval.cc | 21 +++++++++++++++++++-- 1 file changed, 19 insertions(+), 2 deletions(-) (limited to 'src/libexpr/eval.cc') diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc index 26739faf69e8..14e5cab7de60 100644 --- a/src/libexpr/eval.cc +++ b/src/libexpr/eval.cc @@ -108,6 +108,7 @@ EvalState::EvalState() , sMeta(symbols.create("meta")) , sName(symbols.create("name")) , sSystem(symbols.create("system")) + , sOverrides(symbols.create("__overrides")) , baseEnv(allocEnv(128)) , baseEnvDispl(0) , staticBaseEnv(false, 0) @@ -428,8 +429,8 @@ void ExprAttrs::eval(EvalState & state, Env & env, Value & v) environment. */ foreach (Attrs::iterator, i, attrs) { nix::Attr & a = (*v.attrs)[i->first]; - mkCopy(a.value, env2.values[displ]); - mkThunk(env2.values[displ++], env2, i->second.first); + mkThunk(a.value, env2, i->second.first); + mkCopy(env2.values[displ++], a.value); a.pos = &i->second.second; } @@ -443,6 +444,22 @@ void ExprAttrs::eval(EvalState & state, Env & env, Value & v) a.pos = &i->second; } + /* If the rec contains an attribute called `__overrides', then + evaluate it, and add the attributes in that set to the rec. + This allows overriding of recursive attributes, which is + otherwise not possible. (You can use the // operator to + replace an attribute, but other attributes in the rec will + still reference the original value, because that value has + been substituted into the bodies of the other attributes. + Hence we need __overrides.) */ + Bindings::iterator overrides = v.attrs->find(state.sOverrides); + if (overrides != v.attrs->end()) { + state.forceAttrs(overrides->second.value); + foreach (Bindings::iterator, i, *overrides->second.value.attrs) { + nix::Attr & a = (*v.attrs)[i->first]; + mkCopy(a.value, i->second.value); + } + } } else { -- cgit 1.4.1