Eliminate needless level of closure indirection (#1085)

This was CR feedback from @swgillespie.

pkg/engine/destroy.go

@@ -23,24 +23,22 @@ func Destroy(u UpdateInfo, events chan<- Event, opts UpdateOptions) (ResourceCha
 	emitter := makeEventEmitter(events, u)
 	return update(ctx, planOptions{
 		UpdateOptions: opts,
-		SourceFunc:    newDestroySourceFunc(),
+		SourceFunc:    newDestroySource,
 		Events:        emitter,
 		Diag:          newEventSink(emitter),
 	})
 }
 
-func newDestroySourceFunc() planSourceFunc {
+func newDestroySource(opts planOptions, proj *workspace.Project, pwd, main string,
-	return func(opts planOptions, proj *workspace.Project, pwd, main string,
+	target *deploy.Target, plugctx *plugin.Context) (deploy.Source, error) {
-		target *deploy.Target, plugctx *plugin.Context) (deploy.Source, error) {
+	// For destroy, we consult the manifest for the plugin versions/ required to destroy it.
-		// For destroy, we consult the manifest for the plugin versions/ required to destroy it.
+	if target != nil && target.Snapshot != nil {
-		if target != nil && target.Snapshot != nil {
+		if err := plugctx.Host.EnsurePlugins(target.Snapshot.Manifest.Plugins); err != nil {
-			if err := plugctx.Host.EnsurePlugins(target.Snapshot.Manifest.Plugins); err != nil {
+			return nil, err
-				return nil, err
-			}
 		}
-
-		// Create a nil source.  This simply returns "nothing" as the new state, which will cause the
-		// engine to destroy the entire existing state.
-		return deploy.NullSource, nil
 	}
+
+	// Create a nil source.  This simply returns "nothing" as the new state, which will cause the
+	// engine to destroy the entire existing state.
+	return deploy.NullSource, nil
 }

pkg/engine/preview.go

@@ -29,7 +29,7 @@ func Preview(u UpdateInfo, events chan<- Event, opts UpdateOptions) error {
 	emitter := makeEventEmitter(events, u)
 	return preview(ctx, planOptions{
 		UpdateOptions: opts,
-		SourceFunc:    newUpdateSourceFunc(),
+		SourceFunc:    newUpdateSource,
 		Events:        emitter,
 		Diag:          newEventSink(emitter),
 	})

pkg/engine/update.go

@@ -41,39 +41,37 @@ func Update(u UpdateInfo, events chan<- Event, opts UpdateOptions) (ResourceChan
 	emitter := makeEventEmitter(events, u)
 	return update(ctx, planOptions{
 		UpdateOptions: opts,
-		SourceFunc:    newUpdateSourceFunc(),
+		SourceFunc:    newUpdateSource,
 		Events:        emitter,
 		Diag:          newEventSink(emitter),
 	})
 }
 
-func newUpdateSourceFunc() planSourceFunc {
+func newUpdateSource(opts planOptions, proj *workspace.Project, pwd, main string,
-	return func(opts planOptions, proj *workspace.Project, pwd, main string,
+	target *deploy.Target, plugctx *plugin.Context) (deploy.Source, error) {
-		target *deploy.Target, plugctx *plugin.Context) (deploy.Source, error) {
+	// Figure out which plugins to load by inspecting the program contents.
-		// Figure out which plugins to load by inspecting the program contents.
+	plugins, err := plugctx.Host.GetRequiredPlugins(plugin.ProgInfo{
-		plugins, err := plugctx.Host.GetRequiredPlugins(plugin.ProgInfo{
+		Proj:    proj,
-			Proj:    proj,
+		Pwd:     pwd,
-			Pwd:     pwd,
+		Program: main,
-			Program: main,
+	})
-		})
+	if err != nil {
-		if err != nil {
+		return nil, err
-			return nil, err
-		}
-
-		// Now ensure that we have loaded up any plugins that the program will need in advance.
-		if err = plugctx.Host.EnsurePlugins(plugins); err != nil {
-			return nil, err
-		}
-
-		// If that succeeded, create a new source that will perform interpretation of the compiled program.
-		// TODO[pulumi/pulumi#88]: we are passing `nil` as the arguments map; we need to allow a way to pass these.
-		return deploy.NewEvalSource(plugctx, &deploy.EvalRunInfo{
-			Proj:    proj,
-			Pwd:     pwd,
-			Program: main,
-			Target:  target,
-		}, opts.DryRun), nil
 	}
+
+	// Now ensure that we have loaded up any plugins that the program will need in advance.
+	if err = plugctx.Host.EnsurePlugins(plugins); err != nil {
+		return nil, err
+	}
+
+	// If that succeeded, create a new source that will perform interpretation of the compiled program.
+	// TODO[pulumi/pulumi#88]: we are passing `nil` as the arguments map; we need to allow a way to pass these.
+	return deploy.NewEvalSource(plugctx, &deploy.EvalRunInfo{
+		Proj:    proj,
+		Pwd:     pwd,
+		Program: main,
+		Target:  target,
+	}, opts.DryRun), nil
 }
 
 func update(info *planContext, opts planOptions) (ResourceChanges, error) {