diff options
| -rw-r--r-- | src/libexpr/primops.cc | 30 | ||||
| -rw-r--r-- | tests/lang/eval-okay-catattrs.exp | 1 | ||||
| -rw-r--r-- | tests/lang/eval-okay-catattrs.nix | 1 |
3 files changed, 32 insertions, 0 deletions
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc index fb37e21a24bf..a1374a05e12d 100644 --- a/src/libexpr/primops.cc +++ b/src/libexpr/primops.cc @@ -1123,6 +1123,35 @@ static void prim_intersectAttrs(EvalState & state, const Pos & pos, Value * * ar } +/* Collect each attribute named `attr' from a list of attribute sets. + Sets that don't contain the named attribute are ignored. + + Example: + catAttrs "a" [{a = 1;} {b = 0;} {a = 2;}] + => [1 2] +*/ +static void prim_catAttrs(EvalState & state, const Pos & pos, Value * * args, Value & v) +{ + Symbol attrName = state.symbols.create(state.forceStringNoCtx(*args[0], pos)); + state.forceList(*args[1], pos); + + Value * res[args[1]->list.length]; + unsigned int found = 0; + + for (unsigned int n = 0; n < args[1]->list.length; ++n) { + Value & v2(*args[1]->list.elems[n]); + state.forceAttrs(v2, pos); + Bindings::iterator i = v2.attrs->find(attrName); + if (i != v2.attrs->end()) + res[found++] = i->value; + } + + state.mkList(v, found); + for (unsigned int n = 0; n < found; ++n) + v.list.elems[n] = res[n]; +} + + /* Return a set containing the names of the formal arguments expected by the function `f'. The value of each attribute is a Boolean denoting whether has a default value. For instance, @@ -1530,6 +1559,7 @@ void EvalState::createBaseEnv() addPrimOp("removeAttrs", 2, prim_removeAttrs); addPrimOp("__listToAttrs", 1, prim_listToAttrs); addPrimOp("__intersectAttrs", 2, prim_intersectAttrs); + addPrimOp("__catAttrs", 2, prim_catAttrs); addPrimOp("__functionArgs", 1, prim_functionArgs); // Lists diff --git a/tests/lang/eval-okay-catattrs.exp b/tests/lang/eval-okay-catattrs.exp new file mode 100644 index 000000000000..b4a1e66d6b8a --- /dev/null +++ b/tests/lang/eval-okay-catattrs.exp @@ -0,0 +1 @@ +[ 1 2 ] diff --git a/tests/lang/eval-okay-catattrs.nix b/tests/lang/eval-okay-catattrs.nix new file mode 100644 index 000000000000..2c3dc10da528 --- /dev/null +++ b/tests/lang/eval-okay-catattrs.nix @@ -0,0 +1 @@ +builtins.catAttrs "a" [ { a = 1; } { b = 0; } { a = 2; } ] |