Export resource change counts from engine (#823)

This PR exports the aggregate resource changes for update and destroy operations. We'll use this information in #636 when summarizing previous updates.

I initially started with a new struct that had fields like `Created`, `Deleted`, `Unchanged`, etc. But it became cumbersome with the seven different type of resource operations we perform. So instead went with the more flexible `map[deploy.StepOp]int`.

pkg/backend/local/backend.go

@@ -139,7 +139,7 @@ func (b *localBackend) Update(stackName tokens.QName, pkg *pack.Package, root st
 
 	go displayEvents(events, done, debug)
 
-	if err = engine.Deploy(update, events, opts); err != nil {
+	if _, err = engine.Deploy(update, events, opts); err != nil {
 		return err
 	}
 
@@ -162,7 +162,7 @@ func (b *localBackend) Destroy(stackName tokens.QName, pkg *pack.Package, root s
 
 	go displayEvents(events, done, debug)
 
-	if err := engine.Destroy(update, events, opts); err != nil {
+	if _, err := engine.Destroy(update, events, opts); err != nil {
 		return err
 	}
 

pkg/engine/deploy.go

@@ -29,7 +29,10 @@ type UpdateOptions struct {
 	Summary              bool                // true if we should only summarize resources and operations.
 }
 
-func Deploy(update Update, events chan<- Event, opts UpdateOptions) error {
+// ResourceChanges contains the aggregate resource changes by operation type.
+type ResourceChanges map[deploy.StepOp]int
+
+func Deploy(update Update, events chan<- Event, opts UpdateOptions) (ResourceChanges, error) {
 	contract.Require(update != nil, "update")
 	contract.Require(events != nil, "events")
 
@@ -37,7 +40,7 @@ func Deploy(update Update, events chan<- Event, opts UpdateOptions) error {
 
 	info, err := planContextFromUpdate(update)
 	if err != nil {
-		return err
+		return nil, err
 	}
 	defer info.Close()
 
@@ -66,25 +69,27 @@ type deployOptions struct {
 	Diag     diag.Sink    // the sink to use for diag'ing.
 }
 
-func deployLatest(info *planContext, opts deployOptions) error {
+func deployLatest(info *planContext, opts deployOptions) (ResourceChanges, error) {
 	result, err := plan(info, opts)
 	if err != nil {
-		return err
+		return nil, err
 	}
+
+	var resourceChanges ResourceChanges
 	if result != nil {
 		defer contract.IgnoreClose(result)
 
 		// Make the current working directory the same as the program's, and restore it upon exit.
 		done, err := result.Chdir()
 		if err != nil {
-			return err
+			return nil, err
 		}
 		defer done()
 
 		if opts.DryRun {
-			// If a dry run, just print the plan, don't actually carry out the deployment.
+			// If a dry run, just print the plan, don't actually carry out the deployment. (Reporting 0 changes.)
 			if err := printPlan(result); err != nil {
-				return err
+				return resourceChanges, err
 			}
 		} else {
 			// Otherwise, we will actually deploy the latest bits.
@@ -99,7 +104,7 @@ func deployLatest(info *planContext, opts deployOptions) error {
 			summary, _, _, err := result.Walk(actions, false)
 			if err != nil && summary == nil {
 				// Something went wrong, and no changes were made.
-				return err
+				return resourceChanges, err
 			}
 			contract.Assert(summary != nil)
 
@@ -107,7 +112,8 @@ func deployLatest(info *planContext, opts deployOptions) error {
 			var footer bytes.Buffer
 
 			// Print out the total number of steps performed (and their kinds), the duration, and any summary info.
-			if c := printChangeSummary(&footer, actions.Ops, false); c != 0 {
+			resourceChanges = ResourceChanges(actions.Ops)
+			if c := printChangeSummary(&footer, resourceChanges, false); c != 0 {
 				footer.WriteString(fmt.Sprintf("%vUpdate duration: %v%v\n",
 					colors.SpecUnimportant, time.Since(start), colors.Reset))
 			}
@@ -121,15 +127,16 @@ func deployLatest(info *planContext, opts deployOptions) error {
 			opts.Events <- stdOutEventWithColor(&footer, opts.Color)
 
 			if err != nil {
-				return err
+				return resourceChanges, err
 			}
 		}
 	}
+
 	if !opts.Diag.Success() {
 		// If any error that wasn't printed above, be sure to make it evident in the output.
-		return goerr.New("One or more errors occurred during this update")
+		return resourceChanges, goerr.New("One or more errors occurred during this update")
 	}
-	return nil
+	return resourceChanges, nil
 }
 
 // deployActions pretty-prints the plan application process as it goes.

pkg/engine/destroy.go

@@ -7,14 +7,14 @@ import (
 	"github.com/pulumi/pulumi/pkg/util/contract"
 )
 
-func Destroy(update Update, events chan<- Event, opts UpdateOptions) error {
+func Destroy(update Update, events chan<- Event, opts UpdateOptions) (ResourceChanges, error) {
 	contract.Require(update != nil, "update")
 
 	defer func() { events <- cancelEvent() }()
 
 	info, err := planContextFromUpdate(update)
 	if err != nil {
-		return err
+		return nil, err
 	}
 	defer info.Close()
 

pkg/engine/plan.go

@@ -157,6 +157,7 @@ func (res *planResult) Close() error {
 	return res.Ctx.Close()
 }
 
+// printPlan prints the plan's result to the plan's Options.Events stream.
 func printPlan(result *planResult) error {
 	// First print config/unchanged/etc. if necessary.
 	var prelude bytes.Buffer
@@ -180,7 +181,7 @@ func printPlan(result *planResult) error {
 
 	// Print a summary of operation counts.
 	var summary bytes.Buffer
-	printChangeSummary(&summary, actions.Ops, true)
+	printChangeSummary(&summary, ResourceChanges(actions.Ops), true)
 	result.Options.Events <- stdOutEventWithColor(&summary, result.Options.Color)
 	return nil
 }
@@ -233,14 +234,15 @@ func printConfig(b *bytes.Buffer, cfg config.Map) {
 	}
 }
 
-func printChangeSummary(b *bytes.Buffer, counts map[deploy.StepOp]int, preview bool) int {
-	changes := 0
-	for op, c := range counts {
+// printChangeSummary writes summary informatiom about the resoures changed to the provided buffer.
+// Returns the total number of resources changed regardless of operation type.
+func printChangeSummary(b *bytes.Buffer, changes ResourceChanges, preview bool) int {
+	changeCount := 0
+	for op, c := range changes {
 		if op != deploy.OpSame {
-			changes += c
+			changeCount += c
 		}
 	}
-
 	var kind string
 	if preview {
 		kind = "previewed"
@@ -249,19 +251,19 @@ func printChangeSummary(b *bytes.Buffer, counts map[deploy.StepOp]int, preview b
 	}
 
 	var changesLabel string
-	if changes == 0 {
+	if changeCount == 0 {
 		kind = "required"
 		changesLabel = "no"
 	} else {
-		changesLabel = strconv.Itoa(changes)
+		changesLabel = strconv.Itoa(changeCount)
 	}
 
-	if changes > 0 || counts[deploy.OpSame] > 0 {
+	if changeCount > 0 || changes[deploy.OpSame] > 0 {
 		kind += ":"
 	}
 
 	b.WriteString(fmt.Sprintf("%vinfo%v: %v %v %v\n",
-		colors.SpecInfo, colors.Reset, changesLabel, plural("change", changes), kind))
+		colors.SpecInfo, colors.Reset, changesLabel, plural("change", changeCount), kind))
 
 	var planTo string
 	if preview {
@@ -271,7 +273,7 @@ func printChangeSummary(b *bytes.Buffer, counts map[deploy.StepOp]int, preview b
 	// Now summarize all of the changes; we print sames a little differently.
 	for _, op := range deploy.StepOps {
 		if op != deploy.OpSame {
-			if c := counts[op]; c > 0 {
+			if c := changes[op]; c > 0 {
 				opDescription := string(op)
 				if !preview {
 					opDescription = op.PastTense()
@@ -281,11 +283,11 @@ func printChangeSummary(b *bytes.Buffer, counts map[deploy.StepOp]int, preview b
 			}
 		}
 	}
-	if c := counts[deploy.OpSame]; c > 0 {
+	if c := changes[deploy.OpSame]; c > 0 {
 		b.WriteString(fmt.Sprintf("      %v %v unchanged\n", c, plural("resource", c)))
 	}
 
-	return changes
+	return changeCount
 }
 
 func plural(s string, c int) string {