test: don't panic when resolving references that haven't been evaluated

.changes/v1.13/BUG FIXES-20250825-125018.yaml

@@ -0,0 +1,5 @@
+kind: BUG FIXES
+body: 'terraform test: prevent panic when resolving incomplete references'
+time: 2025-08-25T12:50:18.511449+02:00
+custom:
+    Issue: "37484"

internal/command/test_test.go

@@ -402,6 +402,11 @@ func TestTest_Runs(t *testing.T) {
 			expectedOut: []string{"3 passed, 0 failed."},
 			code:        0,
 		},
+		"expect-failures-assertions": {
+			expectedOut: []string{"0 passed, 1 failed."},
+			expectedErr: []string{"Test assertion failed"},
+			code:        1,
+		},
 	}
 	for name, tc := range tcs {
 		t.Run(name, func(t *testing.T) {

internal/command/testdata/test/expect-failures-assertions/child/main.tf

@@ -0,0 +1,12 @@
+
+variable "input" {
+  type = string
+}
+
+resource "test_resource" "resource" {
+  value = var.input
+}
+
+output "output" {
+  value = test_resource.resource.value
+}

internal/command/testdata/test/expect-failures-assertions/main.tf

@@ -0,0 +1,36 @@
+
+variable "input" {
+  type = string
+
+  validation {
+    condition = var.input == "allow"
+    error_message = "invalid input value"
+  }
+}
+
+variable "followup" {
+  type = string
+  default = "allow"
+
+  validation {
+    condition = var.followup == var.input
+    error_message = "followup must match input"
+  }
+}
+
+locals {
+  input = var.followup
+}
+
+module "child" {
+  source = "./child"
+  input = var.input
+}
+
+resource "test_resource" "resource" {
+  value = local.input
+}
+
+output "output" {
+  value = var.input
+}

internal/command/testdata/test/expect-failures-assertions/main.tftest.hcl

@@ -0,0 +1,41 @@
+
+// this test runs assertions againsts parts of the module that should not
+// have executed because of the expected failure. this should be an error
+// in the test, but it shouldn't panic or anything like that.
+
+run "fail" {
+  variables {
+    input = "deny"
+  }
+
+  command = plan
+
+  expect_failures = [
+    var.input,
+  ]
+
+  assert {
+    condition = var.followup == "deny"
+    error_message = "bad input"
+  }
+
+  assert {
+    condition = local.input == "deny"
+    error_message = "bad local"
+  }
+
+  assert {
+    condition = module.child.output == "deny"
+    error_message = "bad module output"
+  }
+
+  assert {
+    condition = test_resource.resource.value == "deny"
+    error_message = "bad resource value"
+  }
+
+  assert {
+    condition = output.output == "deny"
+    error_message = "bad output"
+  }
+}

internal/instances/expander.go

@@ -181,6 +181,21 @@ func (e *Expander) ExpandAbsModuleCall(addr addrs.AbsModuleCall) (keyType addrs.
 	return keyType, instKeys, true
 }
 
+// AbsModuleCallExpanded checks if the specified module call has been visited
+// and expanded previously.
+func (e *Expander) AbsModuleCallExpanded(addr addrs.AbsModuleCall) bool {
+	e.mu.RLock()
+	defer e.mu.RUnlock()
+
+	expParent, ok := e.findModule(addr.Module)
+	if !ok {
+		return false
+	}
+
+	_, ok = expParent.moduleCalls[addr.Call]
+	return ok
+}
+
 // expandModule allows skipping unexpanded module addresses by setting skipUnregistered to true.
 // This is used by instances.Set, which is only concerned with the expanded
 // instances, and should not panic when looking up unknown addresses.
@@ -450,6 +465,20 @@ func (e *Expander) ResourceInstanceKeys(addr addrs.AbsResource) (keyType addrs.I
 	return exp.instanceKeys()
 }
 
+// ResourceInstanceExpanded checks if the specified resource has been visited
+// and expanded previously.
+func (e *Expander) ResourceInstanceExpanded(addr addrs.AbsResource) bool {
+	e.mu.RLock()
+	defer e.mu.RUnlock()
+
+	parentMod, known := e.findModule(addr.Module)
+	if !known {
+		return false
+	}
+	_, ok := parentMod.resources[addr.Resource]
+	return ok
+}
+
 // AllInstances returns a set of all of the module and resource instances known
 // to the expander.
 //

internal/terraform/evaluate.go

@@ -342,8 +342,11 @@ func (d *evaluationStateData) GetLocalValue(addr addrs.LocalValue, rng tfdiags.S
 		return cty.DynamicVal, diags
 	}
 
-	val := d.Evaluator.NamedValues.GetLocalValue(addr.Absolute(d.ModulePath))
-	return val, diags
+	if target := addr.Absolute(d.ModulePath); d.Evaluator.NamedValues.HasLocalValue(target) {
+		return d.Evaluator.NamedValues.GetLocalValue(addr.Absolute(d.ModulePath)), diags
+	}
+
+	return cty.DynamicVal, diags
 }
 
 func (d *evaluationStateData) GetModule(addr addrs.ModuleCall, rng tfdiags.SourceRange) (cty.Value, tfdiags.Diagnostics) {
@@ -541,6 +544,21 @@ func (d *evaluationStateData) GetResource(addr addrs.Resource, rng tfdiags.Sourc
 	// result for _all_ of its work, rather than continuing to duplicate a bunch
 	// of the logic we've tried to encapsulate over ther already.
 	if d.Operation == walkPlan || d.Operation == walkApply {
+		if !d.Evaluator.Instances.ResourceInstanceExpanded(addr.Absolute(moduleAddr)) {
+			// Then we've asked for a resource that hasn't been evaluated yet.
+			// This means that either something has gone wrong in the graph or
+			// the console or test command has an errored plan and is attempting
+			// to load an invalid resource from it.
+
+			unknownVal := cty.DynamicVal
+
+			// If an ephemeral resource is deferred we need to mark the returned unknown value as ephemeral
+			if addr.Mode == addrs.EphemeralResourceMode {
+				unknownVal = unknownVal.Mark(marks.Ephemeral)
+			}
+			return unknownVal, diags
+		}
+
 		if _, _, hasUnknownKeys := d.Evaluator.Instances.ResourceInstanceKeys(addr.Absolute(moduleAddr)); hasUnknownKeys {
 			// There really isn't anything interesting we can do in this situation,
 			// because it means we have an unknown for_each/count, in which case