From e87c78ad6b30dd29ed9363051452bb9c455ae534 Mon Sep 17 00:00:00 2001
From: Yusuke Kuoka <ykuoka@gmail.com>
Date: Sun, 29 Nov 2020 14:27:28 +0900
Subject: [PATCH] Fix dead-lock in checkoutSources

---
 pkg/app/source.go | 34 +++++++++++++++++++++-------------
 1 file changed, 21 insertions(+), 13 deletions(-)

diff --git a/pkg/app/source.go b/pkg/app/source.go
index bb753a5..7d32987 100644
--- a/pkg/app/source.go
+++ b/pkg/app/source.go
@@ -10,40 +10,44 @@ import (
 )
 
 func (app *App) checkoutSources(_ *EventLogger, jobCtx *JobContext, sources []Source, concurrency int) error {
+	if len(sources) == 0 {
+		return nil
+	}
+
 	type result struct {
 		id  string
 		dir string
 	}
 
-	inputs := make(chan Source)
+	sourceCh := make(chan Source)
 
-	results := make(chan result)
+	resultCh := make(chan result)
 
-	eg, ctx := errgroup.WithContext(context.Background())
+	sourceWorkers, ctx := errgroup.WithContext(context.Background())
 
 	for i := 0; i < concurrency; i++ {
-		eg.Go(func() error {
-			for src := range inputs {
+		sourceWorkers.Go(func() error {
+			for src := range sourceCh {
 				dir, err := app.sourceClient.ExtractSource(ctx, src.Kind, src.Namepsace, src.Name)
 				if err != nil {
 					return xerrors.Errorf("extracting source: %w", err)
 				}
 
-				results <- result{id: src.ID, dir: dir}
+				resultCh <- result{id: src.ID, dir: dir}
 			}
 
 			return nil
 		})
 	}
 
-	srcs := map[string]cty.Value{}
+	results := map[string]cty.Value{}
 
 	wg := &sync.WaitGroup{}
 	wg.Add(1)
 
 	go func() {
-		for src := range results {
-			srcs[src.id] = cty.MapVal(map[string]cty.Value{
+		for src := range resultCh {
+			results[src.id] = cty.MapVal(map[string]cty.Value{
 				"dir": cty.StringVal(src.dir),
 			})
 		}
@@ -52,18 +56,22 @@ func (app *App) checkoutSources(_ *EventLogger, jobCtx *JobContext, sources []So
 	}()
 
 	for _, src := range sources {
-		inputs <- src
+		sourceCh <- src
 	}
 
-	if err := eg.Wait(); err != nil {
+	close(sourceCh)
+
+	if err := sourceWorkers.Wait(); err != nil {
 		return xerrors.Errorf("waiting for workers: %w", err)
 	}
 
+	close(resultCh)
+
 	wg.Wait()
 
-	if len(srcs) > 0 {
+	if len(results) > 0 {
 		// Cuz calling cty.MapVal on an empty map panics by its nature
-		jobCtx.evalContext.Variables["source"] = cty.MapVal(srcs)
+		jobCtx.evalContext.Variables["source"] = cty.MapVal(results)
 	}
 
 	return nil