Merge pull request #15566 from hashicorp/jbardin/state-serial

Add warning to mismatched plan state

backend/local/backend_local.go

@@ -49,6 +49,10 @@ func (b *Local) context(op *backend.Operation) (*terraform.Context, state.State,
 	}
 
 	// Load our state
+	// By the time we get here, the backend creation code in "command" took
+	// care of making s.State() return a state compatible with our plan,
+	// if any, so we can safely pass this value in both the plan context
+	// and new context cases below.
 	opts.State = s.State()
 
 	// Build the context

terraform/plan.go

@@ -6,6 +6,7 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"log"
 	"sync"
 
 	"github.com/hashicorp/terraform/config/module"
@@ -43,7 +44,11 @@ type Plan struct {
 // Context returns a Context with the data encapsulated in this plan.
 //
 // The following fields in opts are overridden by the plan: Config,
-// Diff, State, Variables.
+// Diff, Variables.
+//
+// If State is not provided, it is set from the plan. If it _is_ provided,
+// it must be Equal to the state stored in plan, but may have a newer
+// serial.
 func (p *Plan) Context(opts *ContextOpts) (*Context, error) {
 	var err error
 	opts, err = p.contextOpts(opts)
@@ -60,11 +65,23 @@ func (p *Plan) contextOpts(base *ContextOpts) (*ContextOpts, error) {
 
 	opts.Diff = p.Diff
 	opts.Module = p.Module
-	opts.State = p.State
 	opts.Targets = p.Targets
-
 	opts.ProviderSHA256s = p.ProviderSHA256s
 
+	if opts.State == nil {
+		opts.State = p.State
+	} else if !opts.State.Equal(p.State) {
+		// Even if we're overriding the state, it should be logically equal
+		// to what's in plan. The only valid change to have made by the time
+		// we get here is to have incremented the serial.
+		//
+		// Due to the fact that serialization may change the representation of
+		// the state, there is little chance that these aren't actually equal.
+		// Log the error condition for reference, but continue with the state
+		// we have.
+		log.Println("[WARNING] Plan state and ContextOpts state are not equal")
+	}
+
 	thisVersion := VersionString()
 	if p.TerraformVersion != "" && p.TerraformVersion != thisVersion {
 		return nil, fmt.Errorf(

terraform/plan_test.go

@@ -118,3 +118,52 @@ func TestReadWritePlan(t *testing.T) {
 		t.Fatalf("bad:\n\n%s\n\nexpected:\n\n%s", actualStr, expectedStr)
 	}
 }
+
+func TestPlanContextOptsOverrideStateGood(t *testing.T) {
+	plan := &Plan{
+		Diff: &Diff{
+			Modules: []*ModuleDiff{
+				{
+					Path: []string{"test"},
+				},
+			},
+		},
+		Module: module.NewTree("test", nil),
+		State: &State{
+			TFVersion: "sigil",
+			Serial:    1,
+		},
+		Vars:    map[string]interface{}{"foo": "bar"},
+		Targets: []string{"baz"},
+
+		TerraformVersion: VersionString(),
+		ProviderSHA256s: map[string][]byte{
+			"test": []byte("placeholder"),
+		},
+	}
+
+	base := &ContextOpts{
+		State: &State{
+			TFVersion: "sigil",
+			Serial:    2,
+		},
+	}
+
+	got, err := plan.contextOpts(base)
+	if err != nil {
+		t.Fatalf("error creating context: %s", err)
+	}
+
+	want := &ContextOpts{
+		Diff:            plan.Diff,
+		Module:          plan.Module,
+		State:           base.State,
+		Variables:       plan.Vars,
+		Targets:         plan.Targets,
+		ProviderSHA256s: plan.ProviderSHA256s,
+	}
+
+	if !reflect.DeepEqual(got, want) {
+		t.Errorf("wrong result\ngot:  %#v\nwant %#v", got, want)
+	}
+}