cmd/go/internal/modfetch: make Repo.Zip write to an io.Writer instead of a temporary file

This will be used to eliminate a redundant copy in CL 145178.

(It also decouples two design points that were previously coupled: the
destination of the zip output and the program logic to write that
output.)

Updates #26794

Change-Id: I6cfd5a33c162c0016a1b83a278003684560a3772
Reviewed-on: https://go-review.googlesource.com/c/151341
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>

src/cmd/go/internal/modfetch/cache.go

@@ -8,6 +8,7 @@ import (
 	"bytes"
 	"encoding/json"
 	"fmt"
+	"io"
 	"io/ioutil"
 	"os"
 	"path/filepath"
@@ -215,8 +216,8 @@ func (r *cachingRepo) GoMod(rev string) ([]byte, error) {
 	return append([]byte(nil), c.text...), nil
 }
 
-func (r *cachingRepo) Zip(version, tmpdir string) (string, error) {
-	return r.r.Zip(version, tmpdir)
+func (r *cachingRepo) Zip(dst io.Writer, version string) error {
+	return r.r.Zip(dst, version)
 }
 
 // Stat is like Lookup(path).Stat(rev) but avoids the

src/cmd/go/internal/modfetch/coderepo.go

@@ -407,25 +407,26 @@ func (r *codeRepo) modPrefix(rev string) string {
 	return r.modPath + "@" + rev
 }
 
-func (r *codeRepo) Zip(version string, tmpdir string) (tmpfile string, err error) {
+func (r *codeRepo) Zip(dst io.Writer, version string) error {
 	rev, dir, _, err := r.findDir(version)
 	if err != nil {
-		return "", err
+		return err
 	}
 	dl, actualDir, err := r.code.ReadZip(rev, dir, codehost.MaxZipFile)
 	if err != nil {
-		return "", err
+		return err
 	}
+	defer dl.Close()
 	if actualDir != "" && !hasPathPrefix(dir, actualDir) {
-		return "", fmt.Errorf("internal error: downloading %v %v: dir=%q but actualDir=%q", r.path, rev, dir, actualDir)
+		return fmt.Errorf("internal error: downloading %v %v: dir=%q but actualDir=%q", r.path, rev, dir, actualDir)
 	}
 	subdir := strings.Trim(strings.TrimPrefix(dir, actualDir), "/")
 
 	// Spool to local file.
-	f, err := ioutil.TempFile(tmpdir, "go-codehost-")
+	f, err := ioutil.TempFile("", "go-codehost-")
 	if err != nil {
 		dl.Close()
-		return "", err
+		return err
 	}
 	defer os.Remove(f.Name())
 	defer f.Close()
@@ -433,35 +434,24 @@ func (r *codeRepo) Zip(version string, tmpdir string) (tmpfile string, err error
 	lr := &io.LimitedReader{R: dl, N: maxSize + 1}
 	if _, err := io.Copy(f, lr); err != nil {
 		dl.Close()
-		return "", err
+		return err
 	}
 	dl.Close()
 	if lr.N <= 0 {
-		return "", fmt.Errorf("downloaded zip file too large")
+		return fmt.Errorf("downloaded zip file too large")
 	}
 	size := (maxSize + 1) - lr.N
 	if _, err := f.Seek(0, 0); err != nil {
-		return "", err
+		return err
 	}
 
 	// Translate from zip file we have to zip file we want.
 	zr, err := zip.NewReader(f, size)
 	if err != nil {
-		return "", err
-	}
-	f2, err := ioutil.TempFile(tmpdir, "go-codezip-")
-	if err != nil {
-		return "", err
+		return err
 	}
 
-	zw := zip.NewWriter(f2)
-	newName := f2.Name()
-	defer func() {
-		f2.Close()
-		if err != nil {
-			os.Remove(newName)
-		}
-	}()
+	zw := zip.NewWriter(dst)
 	if subdir != "" {
 		subdir += "/"
 	}
@@ -472,12 +462,12 @@ func (r *codeRepo) Zip(version string, tmpdir string) (tmpfile string, err error
 		if topPrefix == "" {
 			i := strings.Index(zf.Name, "/")
 			if i < 0 {
-				return "", fmt.Errorf("missing top-level directory prefix")
+				return fmt.Errorf("missing top-level directory prefix")
 			}
 			topPrefix = zf.Name[:i+1]
 		}
 		if !strings.HasPrefix(zf.Name, topPrefix) {
-			return "", fmt.Errorf("zip file contains more than one top-level directory")
+			return fmt.Errorf("zip file contains more than one top-level directory")
 		}
 		dir, file := path.Split(zf.Name)
 		if file == "go.mod" {
@@ -497,11 +487,12 @@ func (r *codeRepo) Zip(version string, tmpdir string) (tmpfile string, err error
 			name = dir[:len(dir)-1]
 		}
 	}
+
 	for _, zf := range zr.File {
 		if topPrefix == "" {
 			i := strings.Index(zf.Name, "/")
 			if i < 0 {
-				return "", fmt.Errorf("missing top-level directory prefix")
+				return fmt.Errorf("missing top-level directory prefix")
 			}
 			topPrefix = zf.Name[:i+1]
 		}
@@ -509,7 +500,7 @@ func (r *codeRepo) Zip(version string, tmpdir string) (tmpfile string, err error
 			continue
 		}
 		if !strings.HasPrefix(zf.Name, topPrefix) {
-			return "", fmt.Errorf("zip file contains more than one top-level directory")
+			return fmt.Errorf("zip file contains more than one top-level directory")
 		}
 		name := strings.TrimPrefix(zf.Name, topPrefix)
 		if !strings.HasPrefix(name, subdir) {
@@ -529,28 +520,28 @@ func (r *codeRepo) Zip(version string, tmpdir string) (tmpfile string, err error
 		}
 		base := path.Base(name)
 		if strings.ToLower(base) == "go.mod" && base != "go.mod" {
-			return "", fmt.Errorf("zip file contains %s, want all lower-case go.mod", zf.Name)
+			return fmt.Errorf("zip file contains %s, want all lower-case go.mod", zf.Name)
 		}
 		if name == "LICENSE" {
 			haveLICENSE = true
 		}
-		size := int64(zf.UncompressedSize)
+		size := int64(zf.UncompressedSize64)
 		if size < 0 || maxSize < size {
-			return "", fmt.Errorf("module source tree too big")
+			return fmt.Errorf("module source tree too big")
 		}
 		maxSize -= size
 
 		rc, err := zf.Open()
 		if err != nil {
-			return "", err
+			return err
 		}
 		w, err := zw.Create(r.modPrefix(version) + "/" + name)
 		lr := &io.LimitedReader{R: rc, N: size + 1}
 		if _, err := io.Copy(w, lr); err != nil {
-			return "", err
+			return err
 		}
 		if lr.N <= 0 {
-			return "", fmt.Errorf("individual file too large")
+			return fmt.Errorf("individual file too large")
 		}
 	}
 
@@ -559,21 +550,15 @@ func (r *codeRepo) Zip(version string, tmpdir string) (tmpfile string, err error
 		if err == nil {
 			w, err := zw.Create(r.modPrefix(version) + "/LICENSE")
 			if err != nil {
-				return "", err
+				return err
 			}
 			if _, err := w.Write(data); err != nil {
-				return "", err
-			}
-		}
+				return err
 			}
-	if err := zw.Close(); err != nil {
-		return "", err
 		}
-	if err := f2.Close(); err != nil {
-		return "", err
 	}
 
-	return f2.Name(), nil
+	return zw.Close()
 }
 
 // hasPathPrefix reports whether the path s begins with the

src/cmd/go/internal/modfetch/coderepo_test.go

@@ -391,7 +391,13 @@ func TestCodeRepo(t *testing.T) {
 				}
 			}
 			if tt.zip != nil || tt.ziperr != "" {
-				zipfile, err := repo.Zip(tt.version, tmpdir)
+				f, err := ioutil.TempFile(tmpdir, tt.version+".zip.")
+				if err != nil {
+					t.Fatalf("ioutil.TempFile: %v", err)
+				}
+				zipfile := f.Name()
+				err = repo.Zip(f, tt.version)
+				f.Close()
 				if err != nil {
 					if tt.ziperr != "" {
 						if err.Error() == tt.ziperr {

src/cmd/go/internal/modfetch/fetch.go

@@ -108,41 +108,47 @@ func downloadZip(mod module.Version, target string) error {
 	if err != nil {
 		return err
 	}
-	tmpfile, err := repo.Zip(mod.Version, os.TempDir())
+	tmpfile, err := ioutil.TempFile("", "go-codezip-")
 	if err != nil {
 		return err
 	}
-	defer os.Remove(tmpfile)
+	defer func() {
+		tmpfile.Close()
+		os.Remove(tmpfile.Name())
+	}()
+	if err := repo.Zip(tmpfile, mod.Version); err != nil {
+		return err
+	}
 
 	// Double-check zip file looks OK.
-	z, err := zip.OpenReader(tmpfile)
+	fi, err := tmpfile.Stat()
+	if err != nil {
+		return err
+	}
+	z, err := zip.NewReader(tmpfile, fi.Size())
 	if err != nil {
 		return err
 	}
 	prefix := mod.Path + "@" + mod.Version + "/"
 	for _, f := range z.File {
 		if !strings.HasPrefix(f.Name, prefix) {
-			z.Close()
 			return fmt.Errorf("zip for %s has unexpected file %s", prefix[:len(prefix)-1], f.Name)
 		}
 	}
-	z.Close()
 
-	hash, err := dirhash.HashZip(tmpfile, dirhash.DefaultHash)
+	hash, err := dirhash.HashZip(tmpfile.Name(), dirhash.DefaultHash)
 	if err != nil {
 		return err
 	}
 	checkOneSum(mod, hash) // check before installing the zip file
-	r, err := os.Open(tmpfile)
-	if err != nil {
+	if _, err := tmpfile.Seek(0, io.SeekStart); err != nil {
 		return err
 	}
-	defer r.Close()
 	w, err := os.Create(target)
 	if err != nil {
 		return err
 	}
-	if _, err := io.Copy(w, r); err != nil {
+	if _, err := io.Copy(w, tmpfile); err != nil {
 		w.Close()
 		return fmt.Errorf("copying: %v", err)
 	}

src/cmd/go/internal/modfetch/proxy.go

@@ -8,7 +8,6 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"net/url"
 	"os"
 	"strings"
@@ -209,39 +208,26 @@ func (p *proxyRepo) GoMod(version string) ([]byte, error) {
 	return data, nil
 }
 
-func (p *proxyRepo) Zip(version string, tmpdir string) (tmpfile string, err error) {
+func (p *proxyRepo) Zip(dst io.Writer, version string) error {
 	var body io.ReadCloser
 	encVer, err := module.EncodeVersion(version)
 	if err != nil {
-		return "", err
+		return err
 	}
 	err = webGetBody(p.url+"/@v/"+pathEscape(encVer)+".zip", &body)
 	if err != nil {
-		return "", err
+		return err
 	}
 	defer body.Close()
 
-	// Spool to local file.
-	f, err := ioutil.TempFile(tmpdir, "go-proxy-download-")
-	if err != nil {
-		return "", err
-	}
-	defer f.Close()
-	maxSize := int64(codehost.MaxZipFile)
-	lr := &io.LimitedReader{R: body, N: maxSize + 1}
-	if _, err := io.Copy(f, lr); err != nil {
-		os.Remove(f.Name())
-		return "", err
+	lr := &io.LimitedReader{R: body, N: codehost.MaxZipFile + 1}
+	if _, err := io.Copy(dst, lr); err != nil {
+		return err
 	}
 	if lr.N <= 0 {
-		os.Remove(f.Name())
-		return "", fmt.Errorf("downloaded zip file too large")
-	}
-	if err := f.Close(); err != nil {
-		os.Remove(f.Name())
-		return "", err
+		return fmt.Errorf("downloaded zip file too large")
 	}
-	return f.Name(), nil
+	return nil
 }
 
 // pathEscape escapes s so it can be used in a path.

src/cmd/go/internal/modfetch/repo.go

@@ -6,8 +6,10 @@ package modfetch
 
 import (
 	"fmt"
+	"io"
 	"os"
 	"sort"
+	"strconv"
 	"time"
 
 	"cmd/go/internal/cfg"
@@ -45,11 +47,8 @@ type Repo interface {
 	// GoMod returns the go.mod file for the given version.
 	GoMod(version string) (data []byte, err error)
 
-	// Zip downloads a zip file for the given version
-	// to a new file in a given temporary directory.
-	// It returns the name of the new file.
-	// The caller should remove the file when finished with it.
-	Zip(version, tmpdir string) (tmpfile string, err error)
+	// Zip writes a zip file for the given version to dst.
+	Zip(dst io.Writer, version string) error
 }
 
 // A Rev describes a single revision in a module repository.
@@ -357,7 +356,11 @@ func (l *loggingRepo) GoMod(version string) ([]byte, error) {
 	return l.r.GoMod(version)
 }
 
-func (l *loggingRepo) Zip(version, tmpdir string) (string, error) {
-	defer logCall("Repo[%s]: Zip(%q, %q)", l.r.ModulePath(), version, tmpdir)()
-	return l.r.Zip(version, tmpdir)
+func (l *loggingRepo) Zip(dst io.Writer, version string) error {
+	dstName := "_"
+	if dst, ok := dst.(interface{ Name() string }); ok {
+		dstName = strconv.Quote(dst.Name())
+	}
+	defer logCall("Repo[%s]: Zip(%s, %q)", l.r.ModulePath(), dstName, version)()
+	return l.r.Zip(dst, version)
 }