ops: handle unknown objects correctly when looking up by index (#763)

Author: Liam Cervante

CHANGELOG.md

@@ -7,6 +7,10 @@
 * Add support for decoding block and attribute source ranges when using `gohcl`. ([#703](https://github.com/hashicorp/hcl/pull/703))
 * hclsyntax: Detect and reject invalid nested splat result. ([#724](https://github.com/hashicorp/hcl/pull/724))
 
+### Bugs Fixed
+
+* Correct handling of unknown objects in Index function. ([#763](https://github.com/hashicorp/hcl/pull/763))
+
 ## v2.23.0 (November 15, 2024)
 
 ### Bugs Fixed

ops.go

@@ -195,9 +195,6 @@ func Index(collection, key cty.Value, srcRange *Range) (cty.Value, Diagnostics)
 				},
 			}
 		}
-		if !collection.IsKnown() {
-			return cty.DynamicVal.WithSameMarks(collection), nil
-		}
 		if !key.IsKnown() {
 			return cty.DynamicVal.WithSameMarks(collection), nil
 		}
@@ -225,6 +222,10 @@ func Index(collection, key cty.Value, srcRange *Range) (cty.Value, Diagnostics)
 			}
 		}
 
+		if !collection.IsKnown() {
+			return cty.UnknownVal(ty.AttributeType(attrName)).WithSameMarks(collection), nil
+		}
+
 		return collection.GetAttr(attrName), nil
 
 	case ty.IsSetType():

ops_test.go

@@ -476,6 +476,21 @@ func TestIndex(t *testing.T) {
 			want: cty.DynamicVal,
 			err:  "Invalid index",
 		},
+		"unknown object": {
+			coll: cty.UnknownVal(cty.Object(map[string]cty.Type{
+				"foo": cty.String,
+			})),
+			key:  cty.StringVal("foo"),
+			want: cty.UnknownVal(cty.String),
+		},
+		"unknown object, invalid index": {
+			coll: cty.UnknownVal(cty.Object(map[string]cty.Type{
+				"foo": cty.String,
+			})),
+			key:  cty.NumberIntVal(0),
+			want: cty.DynamicVal,
+			err:  "Invalid index",
+		},
 	}
 
 	for name, tc := range tests {