From eb14f8319bdc0b705af9cb2f6dffb804ed5a29da Mon Sep 17 00:00:00 2001
From: Mahmood Ali <mahmood@hashicorp.com>
Date: Fri, 29 Jan 2021 09:15:10 -0500
Subject: [PATCH] Use UndefinedVariable

Use UndefinedVariable to avoid the overloading usage of Unknown in the
library.
---
 eval_context.go |  4 ++--
 traversal.go    | 14 ++++++--------
 2 files changed, 8 insertions(+), 10 deletions(-)

diff --git a/eval_context.go b/eval_context.go
index e0822b7b..945f6ecf 100644
--- a/eval_context.go
+++ b/eval_context.go
@@ -12,9 +12,9 @@ type EvalContext struct {
 	Functions map[string]function.Function
 	parent    *EvalContext
 
-	// UnknownVariable handles when an unknown variable is referenced.
+	// UndefinedVariable is called when an undefined variable is referenced.
 	// This handler is experimental and may change in the future.
-	UnknownVariable func(Traversal) (cty.Value, error)
+	UndefinedVariable func(Traversal) (cty.Value, Diagnostics)
 }
 
 // NewChild returns a new EvalContext that is a child of the receiver.
diff --git a/traversal.go b/traversal.go
index cd66be59..2b579a41 100644
--- a/traversal.go
+++ b/traversal.go
@@ -70,10 +70,10 @@ func (t Traversal) TraverseAbs(ctx *EvalContext) (cty.Value, Diagnostics) {
 
 	thisCtx := ctx
 	hasNonNil := false
-	var unknownHandler func(Traversal) (cty.Value, error)
+	var undefinedHandler func(Traversal) (cty.Value, Diagnostics)
 	for thisCtx != nil {
-		if unknownHandler == nil && thisCtx.UnknownVariable != nil {
-			unknownHandler = thisCtx.UnknownVariable
+		if undefinedHandler == nil && thisCtx.UndefinedVariable != nil {
+			undefinedHandler = thisCtx.UndefinedVariable
 		}
 
 		if thisCtx.Variables == nil {
@@ -88,11 +88,9 @@ func (t Traversal) TraverseAbs(ctx *EvalContext) (cty.Value, Diagnostics) {
 		thisCtx = thisCtx.parent
 	}
 
-	if unknownHandler != nil {
-		v, err := unknownHandler(t)
-		if err == nil {
-			return v, nil
-		}
+	if undefinedHandler != nil {
+		v, diags := undefinedHandler(t)
+		return v, diags
 	}
 
 	if !hasNonNil {