cue: fix default handling for new evaluator

The new evaluator did not erase the Conjuncts field
for disjunctions. We plan to record the actual conjuncts that
went in to a disjunct for the new evaluator, but this has not
been implemented yet.

The API depended on the Conjuncts to be nil for disjuncts.
We mimic this old behavior, for now, until we have the above
implemented.

Also, the old evaluator would filter default values from the
original expression. This did not handle the ConjunctGroup
case yet. This CL implements that.

Issue #3060

Signed-off-by: Marcel van Lohuizen <[email protected]>
Change-Id: I1e8e653ede94f54df6f9e99f50b2931ef3e3674f
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1194048
Unity-Result: CUE porcuepine <[email protected]>
Reviewed-by: Daniel Martí <[email protected]>
TryBot-Result: CUEcueckoo <[email protected]>

Author: mpvl

cue/types_test.go

@@ -1784,8 +1784,6 @@ func TestDefaults(t *testing.T) {
 	}}
 	for _, tc := range testCases {
 		runMatrix(t, tc.value, func(t *testing.T, cfg *evalConfig) {
-			TODO_V3(t, cfg)
-
 			v := cfg.getValue(t, "a: "+tc.value).Lookup("a")
 
 			v = v.Eval()

internal/core/adt/default.go

@@ -127,6 +127,22 @@ func stripNonDefaults(elem Elem) (r Elem, stripped bool) {
 		}
 		return x, false
 
+	case *ConjunctGroup:
+		// NOTE: this code requires allocations unconditional. This should be
+		// mitigated once we optimize conjunct groupings.
+		isNew := false
+		var a ConjunctGroup = make([]Conjunct, len(*x))
+		for i, c := range *x {
+			a[i].x, ok = stripNonDefaults(c.Expr())
+			if ok {
+				isNew = true
+			}
+		}
+		if isNew {
+			return &a, true
+		}
+		return x, false
+
 	default:
 		return x, false
 	}

internal/core/adt/disjunct2.go

@@ -453,6 +453,14 @@ func (n *nodeContext) finalizeDisjunctions() {
 		return
 	}
 
+	// TODO: we clear the Conjuncts to be compatible with the old evaluator.
+	// This is especially relevant for the API. Ideally, though, we should
+	// update Conjuncts to reflect the actual conjunct that went into the
+	// disjuncts.
+	for _, x := range n.disjuncts {
+		x.node.Conjuncts = nil
+	}
+
 	a := make([]Value, len(n.disjuncts))
 	p := 0
 	hasDefaults := false