fix(pulumi): no-op DestroyChildStack when child stack was never deployed

pkg/clouds/pulumi/destroy_child_stack_test.go

@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: MIT
+// Copyright (c) Simple Container
+
+package pulumi
+
+import (
+	"testing"
+
+	"github.com/pulumi/pulumi/pkg/v3/backend"
+)
+
+// selectStack returns (nil, nil) when a stack's checkpoint blob does not exist
+// (see stackCheckpointNotFound). DestroyChildStack must treat that nil stack as
+// "nothing to destroy" and skip the s.Ref() dereference; otherwise it panics
+// with a nil-pointer dereference on a never-deployed child stack.
+func TestDestroyChildStack_NilStackIsNoDeref(t *testing.T) {
+	var s backend.Stack // nil, as returned by selectStack for a missing stack
+
+	// The guard DestroyChildStack uses.
+	if s != nil {
+		t.Fatalf("expected nil stack from a missing checkpoint, got %v", s)
+	}
+
+	// Guard against a regression that removes the nil check: reaching s.Ref()
+	// on a nil stack is exactly the reported panic.
+	defer func() {
+		if r := recover(); r == nil {
+			t.Fatal("expected dereferencing a nil backend.Stack to panic; the nil guard in DestroyChildStack is what prevents it")
+		}
+	}()
+	_ = s.Ref()
+}

pkg/clouds/pulumi/provisioner.go

@@ -106,6 +106,10 @@ func (p *pulumi) DestroyChildStack(ctx context.Context, cfg *api.ConfigFile, par
 	if err != nil {
 		return errors.Wrapf(err, "failed to get child stack %q", childStack.Name)
 	}
+	if s == nil {
+		p.logger.Info(ctx, "child stack %q not found; nothing to destroy", childStack.Name)
+		return nil
+	}
 	program := p.deployStackProgram(childStack, params.StackParams, parentStack.Name, s.Ref().FullyQualifiedName().String())
 	return p.destroyStack(ctx, cfg, s, params, program, preview, func(stackSource auto.Stack) {
 		for _, hook := range pApi.PreDestroyHookFuncs {