From a86c15bb61ed943adad5f3fcf00d0d04b4fbbe27 Mon Sep 17 00:00:00 2001
From: CrazyMax <1951866+crazy-max@users.noreply.github.com>
Date: Thu, 17 Sep 2026 12:19:43 +0200
Subject: [PATCH] bake: report undefined variables correctly

Signed-off-by: CrazyMax <1951866+crazy-max@users.noreply.github.com>
---
 bake/hcl_test.go            | 12 ++++++++++++
 bake/hclparser/hclparser.go | 12 ++++++++----
 2 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/bake/hcl_test.go b/bake/hcl_test.go
index c57ac78213b7..31aac914c2d0 100644
--- a/bake/hcl_test.go
+++ b/bake/hcl_test.go
@@ -598,6 +598,18 @@ func TestHCLVariableCycle(t *testing.T) {
 	require.Contains(t, err.Error(), "variable cycle not allowed")
 }
 
+func TestHCLUndefinedVariable(t *testing.T) {
+	dt := []byte(`
+		target "app" {
+			dockerfile = "${FOO}${FOO}"
+		}
+		`)
+
+	_, err := ParseFile(dt, "docker-bake.hcl")
+	require.ErrorContains(t, err, "Unknown variable")
+	require.NotContains(t, err.Error(), "variable cycle not allowed")
+}
+
 func TestHCLAttrs(t *testing.T) {
 	dt := []byte(`
 		FOO="abc"
diff --git a/bake/hclparser/hclparser.go b/bake/hclparser/hclparser.go
index ec7bf19036e0..4f0ecc7566fb 100644
--- a/bake/hclparser/hclparser.go
+++ b/bake/hclparser/hclparser.go
@@ -268,6 +268,13 @@ func (p *parser) resolveValue(ectx *hcl.EvalContext, name string) (err error) {
 	if _, ok := ectx.Variables[name]; ok {
 		return nil
 	}
+	if _, ok := p.opt.Vars[name]; !ok {
+		if _, ok := p.attrs[name]; !ok {
+			if _, ok := p.vars[name]; !ok {
+				return errors.Wrapf(errUndefined{}, "variable %q does not exist", name)
+			}
+		}
+	}
 	if _, ok := p.progressV[key(ectx, name)]; ok {
 		return errors.Errorf("variable cycle not allowed for %s", name)
 	}
@@ -292,10 +299,7 @@ func (p *parser) resolveValue(ectx *hcl.EvalContext, name string) (err error) {
 	varType, typeSpecified := cty.DynamicPseudoType, false
 	def, ok := p.attrs[name]
 	if !ok {
-		vr, ok := p.vars[name]
-		if !ok {
-			return errors.Wrapf(errUndefined{}, "variable %q does not exist", name)
-		}
+		vr := p.vars[name]
 		def = vr.Default
 		ectx = p.ectx
 		varType, diags = typeConstraint(vr.Type)