Make the pre-destroy refresh a full plan

internal/terraform/context_plan.go

@@ -33,6 +33,16 @@ type PlanOpts struct {
 	// instance using its corresponding provider.
 	SkipRefresh bool
 
+	// PreDestroyRefresh indicated that this is being passed to a plan used to
+	// refresh the state immediately before a destroy plan.
+	// FIXME: This is a temporary fix to allow the pre-destroy refresh to
+	// succeed. The refreshing operation during destroy must be a special case,
+	// which can allow for missing instances in the state, and avoid blocking
+	// on failing condition tests. The destroy plan itself should be
+	// responsible for this special case of refreshing, and the separate
+	// pre-destroy plan removed entirely.
+	PreDestroyRefresh bool
+
 	// SetVariables are the raw values for root module variables as provided
 	// by the user who is requesting the run, prior to any normalization or
 	// substitution of defaults. See the documentation for the InputValue
@@ -337,8 +347,16 @@ func (c *Context) destroyPlan(config *configs.Config, prevRunState *states.State
 	if !opts.SkipRefresh && !prevRunState.Empty() {
 		log.Printf("[TRACE] Context.destroyPlan: calling Context.plan to get the effect of refreshing the prior state")
 		refreshOpts := *opts
-		refreshOpts.Mode = plans.RefreshOnlyMode
-		refreshPlan, refreshDiags := c.refreshOnlyPlan(config, prevRunState, &refreshOpts)
+		refreshOpts.Mode = plans.NormalMode
+		refreshOpts.PreDestroyRefresh = true
+
+		// FIXME: A normal plan is required here to refresh the state, because
+		// the state and configuration may not match during a destroy, and a
+		// normal refresh plan can fail with evaluation errors. In the future
+		// the destroy plan should take care of refreshing instances itself,
+		// where the special cases of evaluation and skipping condition checks
+		// can be done.
+		refreshPlan, refreshDiags := c.plan(config, prevRunState, &refreshOpts)
 		if refreshDiags.HasErrors() {
 			// NOTE: Normally we'd append diagnostics regardless of whether
 			// there are errors, just in case there are warnings we'd want to
@@ -558,6 +576,7 @@ func (c *Context) planGraph(config *configs.Config, prevRunState *states.State,
 			Targets:            opts.Targets,
 			ForceReplace:       opts.ForceReplace,
 			skipRefresh:        opts.SkipRefresh,
+			preDestroyRefresh:  opts.PreDestroyRefresh,
 			Operation:          walkPlan,
 		}).Build(addrs.RootModuleInstance)
 		return graph, walkPlan, diags

internal/terraform/context_plan2_test.go

@@ -3827,3 +3827,103 @@ resource "test_object" "b" {
 	_, diags = ctx.Plan(m, state, opts)
 	assertNoErrors(t, diags)
 }
+
+func TestContext2Plan_destroyPartialState(t *testing.T) {
+	m := testModuleInline(t, map[string]string{
+		"main.tf": `
+resource "test_object" "a" {
+}
+
+output "out" {
+  value = module.mod.out
+}
+
+module "mod" {
+  source = "./mod"
+}
+`,
+
+		"./mod/main.tf": `
+resource "test_object" "a" {
+  count = 2
+
+  lifecycle {
+    precondition {
+	  # test_object_b has already been destroyed, so referencing the first
+      # instance must not fail during a destroy plan.
+      condition = test_object.b[0].test_string == "invalid"
+      error_message = "should not block destroy"
+    }
+    precondition {
+      # this failing condition should bot block a destroy plan
+      condition = !local.continue
+      error_message = "should not block destroy"
+    }
+  }
+}
+
+resource "test_object" "b" {
+  count = 2
+}
+
+locals {
+  continue = true
+}
+
+output "out" {
+  # the reference to test_object.b[0] may not be valid during a destroy plan,
+  # but should not fail.
+  value = local.continue ? test_object.a[1].test_string != "invalid"  && test_object.b[0].test_string != "invalid" : false
+
+  precondition {
+    # test_object_b has already been destroyed, so referencing the first
+    # instance must not fail during a destroy plan.
+    condition = test_object.b[0].test_string == "invalid"
+    error_message = "should not block destroy"
+  }
+  precondition {
+    # this failing condition should bot block a destroy plan
+    condition = test_object.a[0].test_string == "invalid"
+    error_message = "should not block destroy"
+  }
+}
+`})
+
+	p := simpleMockProvider()
+
+	// This state could be the result of a failed destroy, leaving only 2
+	// remaining instances. We want to be able to continue the destroy to
+	// remove everything without blocking on invalid references or failing
+	// conditions.
+	state := states.NewState()
+	mod := state.EnsureModule(addrs.RootModuleInstance.Child("mod", addrs.NoKey))
+	mod.SetResourceInstanceCurrent(
+		mustResourceInstanceAddr("test_object.a[0]").Resource,
+		&states.ResourceInstanceObjectSrc{
+			Status:       states.ObjectTainted,
+			AttrsJSON:    []byte(`{"test_string":"current"}`),
+			Dependencies: []addrs.ConfigResource{},
+		},
+		mustProviderConfig(`provider["registry.terraform.io/hashicorp/test"]`),
+	)
+	mod.SetResourceInstanceCurrent(
+		mustResourceInstanceAddr("test_object.a[1]").Resource,
+		&states.ResourceInstanceObjectSrc{
+			Status:       states.ObjectTainted,
+			AttrsJSON:    []byte(`{"test_string":"current"}`),
+			Dependencies: []addrs.ConfigResource{},
+		},
+		mustProviderConfig(`provider["registry.terraform.io/hashicorp/test"]`),
+	)
+
+	ctx := testContext2(t, &ContextOpts{
+		Providers: map[addrs.Provider]providers.Factory{
+			addrs.NewDefaultProvider("test"): testProviderFuncFixed(p),
+		},
+	})
+
+	_, diags := ctx.Plan(m, state, &PlanOpts{
+		Mode: plans.DestroyMode,
+	})
+	assertNoErrors(t, diags)
+}

internal/terraform/graph_builder_plan.go

@@ -49,6 +49,11 @@ type PlanGraphBuilder struct {
 	// skipRefresh indicates that we should skip refreshing managed resources
 	skipRefresh bool
 
+	// preDestroyRefresh indicates that we are executing the refresh which
+	// happens immediately before a destroy plan, which happens to use the
+	// normal planing mode so skipPlanChanges cannot be set.
+	preDestroyRefresh bool
+
 	// skipPlanChanges indicates that we should skip the step of comparing
 	// prior state with configuration and generating planned changes to
 	// resource instances. (This is for the "refresh only" planning mode,
@@ -111,7 +116,7 @@ func (b *PlanGraphBuilder) Steps() []GraphTransformer {
 		&LocalTransformer{Config: b.Config},
 		&OutputTransformer{
 			Config:      b.Config,
-			RefreshOnly: b.skipPlanChanges,
+			RefreshOnly: b.skipPlanChanges || b.preDestroyRefresh,
 			PlanDestroy: b.Operation == walkPlanDestroy,
 
 			// NOTE: We currently treat anything built with the plan graph
@@ -214,6 +219,7 @@ func (b *PlanGraphBuilder) initPlan() {
 			NodeAbstractResource: a,
 			skipRefresh:          b.skipRefresh,
 			skipPlanChanges:      b.skipPlanChanges,
+			preDestroyRefresh:    b.preDestroyRefresh,
 			forceReplace:         b.ForceReplace,
 		}
 	}

internal/terraform/node_resource_abstract_instance.go

@@ -37,6 +37,8 @@ type NodeAbstractResourceInstance struct {
 	storedProviderConfig addrs.AbsProviderConfig
 
 	Dependencies []addrs.ConfigResource
+
+	preDestroyRefresh bool
 }
 
 // NewNodeAbstractResourceInstance creates an abstract resource instance graph
@@ -682,6 +684,11 @@ func (n *NodeAbstractResourceInstance) plan(
 		return plan, state, keyData, diags.Append(err)
 	}
 
+	checkRuleSeverity := tfdiags.Error
+	if n.preDestroyRefresh {
+		checkRuleSeverity = tfdiags.Warning
+	}
+
 	if plannedChange != nil {
 		// If we already planned the action, we stick to that plan
 		createBeforeDestroy = plannedChange.Action == plans.CreateThenDelete
@@ -708,7 +715,7 @@ func (n *NodeAbstractResourceInstance) plan(
 		addrs.ResourcePrecondition,
 		n.Config.Preconditions,
 		ctx, n.Addr, keyData,
-		tfdiags.Error,
+		checkRuleSeverity,
 	)
 	diags = diags.Append(checkDiags)
 	if diags.HasErrors() {

internal/terraform/node_resource_plan.go

@@ -25,6 +25,8 @@ type nodeExpandPlannableResource struct {
 	// skipRefresh indicates that we should skip refreshing individual instances
 	skipRefresh bool
 
+	preDestroyRefresh bool
+
 	// skipPlanChanges indicates we should skip trying to plan change actions
 	// for any instances.
 	skipPlanChanges bool
@@ -328,6 +330,7 @@ func (n *nodeExpandPlannableResource) resourceInstanceSubgraph(ctx EvalContext,
 		a.ProviderMetas = n.ProviderMetas
 		a.dependsOn = n.dependsOn
 		a.Dependencies = n.dependencies
+		a.preDestroyRefresh = n.preDestroyRefresh
 
 		return &NodePlannableResourceInstance{
 			NodeAbstractResourceInstance: a,

internal/terraform/node_resource_plan_instance.go

@@ -83,7 +83,7 @@ func (n *NodePlannableResourceInstance) dataResourceExecute(ctx EvalContext) (di
 	}
 
 	checkRuleSeverity := tfdiags.Error
-	if n.skipPlanChanges {
+	if n.skipPlanChanges || n.preDestroyRefresh {
 		checkRuleSeverity = tfdiags.Warning
 	}
 
@@ -128,6 +128,11 @@ func (n *NodePlannableResourceInstance) managedResourceExecute(ctx EvalContext)
 	var change *plans.ResourceInstanceChange
 	var instanceRefreshState *states.ResourceInstanceObject
 
+	checkRuleSeverity := tfdiags.Error
+	if n.skipPlanChanges || n.preDestroyRefresh {
+		checkRuleSeverity = tfdiags.Warning
+	}
+
 	_, providerSchema, err := getProvider(ctx, n.ResolvedProvider)
 	diags = diags.Append(err)
 	if diags.HasErrors() {
@@ -280,7 +285,7 @@ func (n *NodePlannableResourceInstance) managedResourceExecute(ctx EvalContext)
 			addrs.ResourcePostcondition,
 			n.Config.Postconditions,
 			ctx, n.ResourceInstanceAddr(), repeatData,
-			tfdiags.Error,
+			checkRuleSeverity,
 		)
 		diags = diags.Append(checkDiags)
 	} else {
@@ -298,7 +303,7 @@ func (n *NodePlannableResourceInstance) managedResourceExecute(ctx EvalContext)
 			addrs.ResourcePrecondition,
 			n.Config.Preconditions,
 			ctx, addr, repeatData,
-			tfdiags.Warning,
+			checkRuleSeverity,
 		)
 		diags = diags.Append(checkDiags)
 
@@ -321,7 +326,7 @@ func (n *NodePlannableResourceInstance) managedResourceExecute(ctx EvalContext)
 			addrs.ResourcePostcondition,
 			n.Config.Postconditions,
 			ctx, addr, repeatData,
-			tfdiags.Warning,
+			checkRuleSeverity,
 		)
 		diags = diags.Append(checkDiags)
 	}