Make assignments to undeclared variables an error (#1941)

terraform/input_value.go

@@ -1,3 +1,6 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: MPL-2.0
+
 package terraform
 
 import (
@@ -50,6 +53,7 @@ func DefaultVariableValues(configs map[string]*Variable) InputValues {
 
 // EnvironmentVariableValues looks up `TF_VAR_*` env variables and returns InputValues.
 // Declared variables are required because the parsing mode of the variable value is type-dependent.
+// However, in the case of environment variables, no error is returned even if the variable is not declared.
 func EnvironmentVariableValues(declVars map[string]*Variable) (InputValues, hcl.Diagnostics) {
 	envVariables := make(InputValues)
 	var diags hcl.Diagnostics
@@ -88,6 +92,7 @@ func EnvironmentVariableValues(declVars map[string]*Variable) (InputValues, hcl.
 
 // ParseVariableValues parses the variable values passed as CLI flags and returns InputValues.
 // Declared variables are required because the parsing mode of the variable value is type-dependent.
+// Return an error if the variable is not declared.
 func ParseVariableValues(vars []string, declVars map[string]*Variable) (InputValues, hcl.Diagnostics) {
 	variables := make(InputValues)
 	var diags hcl.Diagnostics
@@ -97,6 +102,7 @@ func ParseVariableValues(vars []string, declVars map[string]*Variable) (InputVal
 		if idx == -1 {
 			diags = diags.Append(&hcl.Diagnostic{
 				Severity: hcl.DiagError,
+				Subject:  &hcl.Range{Filename: "<input-value>", Start: hcl.InitialPos, End: hcl.InitialPos},
 				Summary:  "invalid variable value format",
 				Detail:   fmt.Sprintf(`"%s" is invalid. Variables must be "key=value" format`, raw),
 			})
@@ -110,7 +116,13 @@ func ParseVariableValues(vars []string, declVars map[string]*Variable) (InputVal
 		if declared {
 			mode = declVar.ParsingMode
 		} else {
-			mode = VariableParseLiteral
+			diags = diags.Append(&hcl.Diagnostic{
+				Severity: hcl.DiagError,
+				Subject:  &hcl.Range{Filename: fmt.Sprintf("<value for var.%s>", name), Start: hcl.InitialPos, End: hcl.InitialPos},
+				Summary:  "Value for undeclared variable",
+				Detail:   fmt.Sprintf("A variable named %q was assigned, but the root module does not declare a variable of that name.", name),
+			})
+			continue
 		}
 
 		val, parseDiags := mode.Parse(name, rawVal)

terraform/input_value_test.go

@@ -172,21 +172,11 @@ func TestParseVariableValues(t *testing.T) {
 			declared: map[string]*Variable{},
 			vars: []string{
 				"foo=bar",
-				"bar=[\"foo\"]",
-				"baz={ foo=\"bar\" }",
 			},
-			want: InputValues{
-				"foo": &InputValue{
-					Value: cty.StringVal("bar"),
-				},
-				"bar": &InputValue{
-					Value: cty.StringVal("[\"foo\"]"),
-				},
-				"baz": &InputValue{
-					Value: cty.StringVal("{ foo=\"bar\" }"),
-				},
+			want: InputValues{},
+			errCheck: func(diags hcl.Diagnostics) bool {
+				return diags.Error() != `<value for var.foo>:1,1-1: Value for undeclared variable; A variable named "foo" was assigned, but the root module does not declare a variable of that name.`
 			},
-			errCheck: neverHappend,
 		},
 		{
 			name: "declared",
@@ -219,7 +209,7 @@ func TestParseVariableValues(t *testing.T) {
 			vars:     []string{"foo"},
 			want:     InputValues{},
 			errCheck: func(diags hcl.Diagnostics) bool {
-				return diags.Error() != `<nil>: invalid variable value format; "foo" is invalid. Variables must be "key=value" format`
+				return diags.Error() != `<input-value>:1,1-1: invalid variable value format; "foo" is invalid. Variables must be "key=value" format`
 			},
 		},
 		{