Merge pull request #30329 from hashicorp/jbardin/module-variable-default

remove synthetic default expression for variables

internal/terraform/context_validate_test.go

@@ -2062,3 +2062,36 @@ output "out" {
 		t.Fatal(diags.ErrWithWarnings())
 	}
 }
+
+func TestContext2Validate_nonNullableVariableDefaultValidation(t *testing.T) {
+	m := testModuleInline(t, map[string]string{
+		"main.tf": `
+ module "first" {
+   source = "./mod"
+   input = null
+ }
+ `,
+
+		"mod/main.tf": `
+ variable "input" {
+   type        = string
+   default     = "default"
+   nullable    = false
+
+   // Validation expressions should receive the default with nullable=false and
+   // a null input.
+   validation {
+     condition     = var.input != null
+     error_message = "Input cannot be null!"
+   }
+ }
+ `,
+	})
+
+	ctx := testContext2(t, &ContextOpts{})
+
+	diags := ctx.Validate(m)
+	if diags.HasErrors() {
+		t.Fatal(diags.ErrWithWarnings())
+	}
+}

internal/terraform/node_module_variable.go

@@ -149,10 +149,10 @@ func (n *nodeModuleVariable) Execute(ctx EvalContext, op walkOperation) (diags t
 
 	switch op {
 	case walkValidate:
-		val, err = n.evalModuleCallArgument(ctx, true)
+		val, err = n.evalModuleVariable(ctx, true)
 		diags = diags.Append(err)
 	default:
-		val, err = n.evalModuleCallArgument(ctx, false)
+		val, err = n.evalModuleVariable(ctx, false)
 		diags = diags.Append(err)
 	}
 	if diags.HasErrors() {
@@ -178,7 +178,7 @@ func (n *nodeModuleVariable) DotNode(name string, opts *dag.DotOpts) *dag.DotNod
 	}
 }
 
-// evalModuleCallArgument produces the value for a particular variable as will
+// evalModuleVariable produces the value for a particular variable as will
 // be used by a child module instance.
 //
 // The result is written into a map, with its key set to the local name of the
@@ -190,7 +190,7 @@ func (n *nodeModuleVariable) DotNode(name string, opts *dag.DotOpts) *dag.DotNod
 // validateOnly indicates that this evaluation is only for config
 // validation, and we will not have any expansion module instance
 // repetition data.
-func (n *nodeModuleVariable) evalModuleCallArgument(ctx EvalContext, validateOnly bool) (cty.Value, error) {
+func (n *nodeModuleVariable) evalModuleVariable(ctx EvalContext, validateOnly bool) (cty.Value, error) {
 	var diags tfdiags.Diagnostics
 	var givenVal cty.Value
 	var errSourceRange tfdiags.SourceRange

internal/terraform/transform_module_variable.go

@@ -3,7 +3,6 @@ package terraform
 import (
 	"fmt"
 
-	"github.com/hashicorp/hcl/v2/hclsyntax"
 	"github.com/hashicorp/terraform/internal/addrs"
 	"github.com/hashicorp/terraform/internal/tfdiags"
 	"github.com/zclconf/go-cty/cty"
@@ -94,13 +93,6 @@ func (t *ModuleVariableTransformer) transformSingle(g *Graph, parent, c *configs
 		var expr hcl.Expression
 		if attr := content.Attributes[v.Name]; attr != nil {
 			expr = attr.Expr
-		} else {
-			// No expression provided for this variable, so we'll make a
-			// synthetic one using the variable's default value.
-			expr = &hclsyntax.LiteralValueExpr{
-				Val:      v.Default,
-				SrcRange: v.DeclRange, // This is not exact, but close enough
-			}
 		}
 
 		// Add a plannable node, as the variable may expand