Merge pull request moby#5254 from tonistiigi/uploadprovider-closer

uploadprovider: allow closing used sources

Author: AkihiroSuda

frontend/dockerfile/dockerfile_test.go

@@ -5311,7 +5311,7 @@ COPY foo /
 	defer c.Close()
 
 	up := uploadprovider.New()
-	url := up.Add(buf)
+	url := up.Add(io.NopCloser(buf))
 
 	_, err = f.Solve(sb.Context(), c, client.SolveOpt{
 		FrontendAttrs: map[string]string{
@@ -5356,7 +5356,7 @@ COPY foo bar
 	defer c.Close()
 
 	up := uploadprovider.New()
-	url := up.Add(buf)
+	url := up.Add(io.NopCloser(buf))
 
 	// repeat with changed default args should match the old cache
 	destDir := t.TempDir()

session/upload/uploadprovider/provider.go

@@ -13,15 +13,15 @@ import (
 )
 
 func New() *Uploader {
-	return &Uploader{m: map[string]io.Reader{}}
+	return &Uploader{m: map[string]io.ReadCloser{}}
 }
 
 type Uploader struct {
 	mu sync.Mutex
-	m  map[string]io.Reader
+	m  map[string]io.ReadCloser
 }
 
-func (hp *Uploader) Add(r io.Reader) string {
+func (hp *Uploader) Add(r io.ReadCloser) string {
 	id := identity.NewID()
 	hp.m[id] = r
 	return "http://buildkit-session/" + id
@@ -51,6 +51,11 @@ func (hp *Uploader) Pull(stream upload.Upload_PullServer) error {
 	hp.mu.Unlock()
 
 	_, err := io.Copy(&writer{stream}, r)
+
+	if err1 := r.Close(); err == nil {
+		err = err1
+	}
+
 	return err
 }