stacks: do not include removed block instances that do not exist in state (#35693)

* stacks: include a warning if a removed block targets a non-existent component

* check plan/apply stages separately

* no warning

internal/stacks/stackruntime/apply_test.go

@@ -3147,8 +3147,6 @@ func TestApply_RemovedBlocks(t *testing.T) {
 	)
 
 	// TODO: Add tests for and implement the following cases:
-	//   - Add a test for a removed block targeting state that has already been
-	//     removed.
 	//   - Add a test for a removed block that forgets instead of destroys.
 
 	tcs := map[string]struct {

internal/stacks/stackruntime/internal/stackeval/removed.go

@@ -104,19 +104,48 @@ func (r *Removed) Instances(ctx context.Context, phase EvalPhase) (map[addrs.Ins
 			return instancesResult[*RemovedInstance]{}, diags
 		}
 
+		// First, evaluate the for_each value to get the set of instances the
+		// user has asked to be removed.
 		result := instancesMap(forEachValue, func(ik addrs.InstanceKey, rd instances.RepetitionData) *RemovedInstance {
 			return newRemovedInstance(r, ik, rd, false)
 		})
 
-		addrs := make([]stackaddrs.AbsComponentInstance, 0, len(result.insts))
-		for _, ci := range result.insts {
-			addrs = append(addrs, ci.Addr())
+		// Now, filter out any instances that are not known to the previous
+		// state. This means the user has targeted a component that (a) never
+		// existed or (b) was removed in a previous operation.
+		//
+		// This stops us emitting planned and applied changes for instances that
+		// do not exist.
+		knownAddrs := make([]stackaddrs.AbsComponentInstance, 0, len(result.insts))
+		knownInstances := make(map[addrs.InstanceKey]*RemovedInstance, len(result.insts))
+		for key, ci := range result.insts {
+			switch phase {
+			case PlanPhase:
+				if r.main.PlanPrevState().HasComponentInstance(ci.Addr()) {
+					knownInstances[key] = ci
+					knownAddrs = append(knownAddrs, ci.Addr())
+					continue
+				}
+			case ApplyPhase:
+				if _, ok := r.main.PlanBeingApplied().Components.GetOk(ci.Addr()); ok {
+					knownInstances[key] = ci
+					knownAddrs = append(knownAddrs, ci.Addr())
+					continue
+				}
+			default:
+				// Otherwise, we're running in a stage that doesn't evaluate
+				// a state or the plan so we'll just include everything.
+				knownInstances[key] = ci
+				knownAddrs = append(knownAddrs, ci.Addr())
+
+			}
 		}
+		result.insts = knownInstances
 
 		h := hooksFromContext(ctx)
 		hookSingle(ctx, h.ComponentExpanded, &hooks.ComponentInstances{
 			ComponentAddr: r.Addr(),
-			InstanceAddrs: addrs,
+			InstanceAddrs: knownAddrs,
 		})
 
 		return result, diags

internal/stacks/stackruntime/plan_test.go

@@ -4724,6 +4724,122 @@ func TestPlan_RemovedBlocks(t *testing.T) {
 				},
 			},
 		},
+		"absent component": {
+			source: filepath.Join("with-single-input", "removed-component"),
+			wantPlanChanges: []stackplan.PlannedChange{
+				&stackplan.PlannedChangeApplyable{
+					Applyable: true,
+				},
+				&stackplan.PlannedChangeHeader{
+					TerraformVersion: version.SemVer,
+				},
+				&stackplan.PlannedChangePlannedTimestamp{
+					PlannedTimestamp: fakePlanTimestamp,
+				},
+			},
+		},
+		"absent component instance": {
+			source: filepath.Join("with-single-input", "removed-component-instance"),
+			initialState: stackstate.NewStateBuilder().
+				AddComponentInstance(stackstate.NewComponentInstanceBuilder(mustAbsComponentInstance("component.self[\"removed\"]")).
+					AddInputVariable("id", cty.StringVal("a")).
+					AddInputVariable("input", cty.StringVal("a"))).
+				AddResourceInstance(stackstate.NewResourceInstanceBuilder().
+					SetAddr(mustAbsResourceInstanceObject("component.self[\"a\"].testing_resource.data")).
+					SetProviderAddr(mustDefaultRootProvider("testing")).
+					SetResourceInstanceObjectSrc(states.ResourceInstanceObjectSrc{
+						Status: states.ObjectReady,
+						AttrsJSON: mustMarshalJSONAttrs(map[string]any{
+							"id":    "a",
+							"value": "a",
+						}),
+					})).
+				Build(),
+			store: stacks_testing_provider.NewResourceStoreBuilder().
+				AddResource("a", cty.ObjectVal(map[string]cty.Value{
+					"id":    cty.StringVal("a"),
+					"value": cty.StringVal("a"),
+				})).
+				Build(),
+			inputs: map[string]cty.Value{
+				"input": cty.SetVal([]cty.Value{
+					cty.StringVal("a"),
+				}),
+				"removed": cty.SetVal([]cty.Value{
+					cty.StringVal("b"), // Doesn't exist!
+				}),
+			},
+			wantPlanChanges: []stackplan.PlannedChange{
+				&stackplan.PlannedChangeApplyable{
+					Applyable: true,
+				},
+				// we're expecting the new component to be created
+				&stackplan.PlannedChangeComponentInstance{
+					Addr:          mustAbsComponentInstance("component.self[\"a\"]"),
+					PlanComplete:  true,
+					PlanApplyable: false, // no changes
+					Action:        plans.Update,
+					PlannedInputValues: map[string]plans.DynamicValue{
+						"id":    mustPlanDynamicValueDynamicType(cty.StringVal("a")),
+						"input": mustPlanDynamicValueDynamicType(cty.StringVal("a")),
+					},
+					PlannedInputValueMarks: map[string][]cty.PathValueMarks{
+						"input": nil,
+						"id":    nil,
+					},
+					PlannedOutputValues: make(map[string]cty.Value),
+					PlannedCheckResults: &states.CheckResults{},
+					PlanTimestamp:       fakePlanTimestamp,
+				},
+				&stackplan.PlannedChangeResourceInstancePlanned{
+					ResourceInstanceObjectAddr: mustAbsResourceInstanceObject("component.self[\"a\"].testing_resource.data"),
+					ChangeSrc: &plans.ResourceInstanceChangeSrc{
+						Addr:        mustAbsResourceInstance("testing_resource.data"),
+						PrevRunAddr: mustAbsResourceInstance("testing_resource.data"),
+						ChangeSrc: plans.ChangeSrc{
+							Action: plans.NoOp,
+							Before: mustPlanDynamicValue(cty.ObjectVal(map[string]cty.Value{
+								"id":    cty.StringVal("a"),
+								"value": cty.StringVal("a"),
+							})),
+							After: mustPlanDynamicValue(cty.ObjectVal(map[string]cty.Value{
+								"id":    cty.StringVal("a"),
+								"value": cty.StringVal("a"),
+							})),
+						},
+						ProviderAddr: mustDefaultRootProvider("testing"),
+					},
+					PriorStateSrc: &states.ResourceInstanceObjectSrc{
+						Status: states.ObjectReady,
+						AttrsJSON: mustMarshalJSONAttrs(map[string]any{
+							"id":    "a",
+							"value": "a",
+						}),
+						Dependencies: make([]addrs.ConfigResource, 0),
+					},
+					ProviderConfigAddr: mustDefaultRootProvider("testing"),
+					Schema:             stacks_testing_provider.TestingResourceSchema,
+				},
+				&stackplan.PlannedChangeHeader{
+					TerraformVersion: version.SemVer,
+				},
+				&stackplan.PlannedChangePlannedTimestamp{
+					PlannedTimestamp: fakePlanTimestamp,
+				},
+				&stackplan.PlannedChangeRootInputValue{
+					Addr: stackaddrs.InputVariable{Name: "input"},
+					Value: cty.SetVal([]cty.Value{
+						cty.StringVal("a"),
+					}),
+				},
+				&stackplan.PlannedChangeRootInputValue{
+					Addr: stackaddrs.InputVariable{Name: "removed"},
+					Value: cty.SetVal([]cty.Value{
+						cty.StringVal("b"),
+					}),
+				},
+			},
+		},
 		"orphaned component": {
 			source: filepath.Join("with-single-input", "removed-component-instance"),
 			initialState: stackstate.NewStateBuilder().