cmd/go: fix typo in sumdb cache path

Put the sumdb cache in the usual pkg/mod/cache/download dir, rather
than the new pkg/mod/download/cache dir which I presume was a typo.

Change-Id: Id162f24db30f509353178ca0c8cc7a4dabc927e1
Reviewed-on: https://go-review.googlesource.com/c/go/+/183318
Run-TryBot: Heschi Kreinick <heschi@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
Reviewed-by: Jay Conrod <jayconrod@google.com>

src/cmd/go/internal/modfetch/sumdb.go

@@ -232,10 +232,10 @@ func (*dbClient) WriteConfig(file string, old, new []byte) error {
 }
 
 // ReadCache reads cached lookups or tiles from
-// GOPATH/pkg/mod/download/cache/sumdb,
+// GOPATH/pkg/mod/cache/download/sumdb,
 // which will be deleted by "go clean -modcache".
 func (*dbClient) ReadCache(file string) ([]byte, error) {
-	targ := filepath.Join(PkgMod, "download/cache/sumdb", file)
+	targ := filepath.Join(PkgMod, "cache/download/sumdb", file)
 	data, err := lockedfile.Read(targ)
 	// lockedfile.Write does not atomically create the file with contents.
 	// There is a moment between file creation and locking the file for writing,
@@ -249,7 +249,7 @@ func (*dbClient) ReadCache(file string) ([]byte, error) {
 
 // WriteCache updates cached lookups or tiles.
 func (*dbClient) WriteCache(file string, data []byte) {
-	targ := filepath.Join(PkgMod, "download/cache/sumdb", file)
+	targ := filepath.Join(PkgMod, "cache/download/sumdb", file)
 	os.MkdirAll(filepath.Dir(targ), 0777)
 	lockedfile.Write(targ, bytes.NewReader(data), 0666)
 }

src/cmd/go/testdata/script/mod_sumdb_cache.txt

@@ -28,7 +28,7 @@ cp go.mod.orig go.mod
 rm go.sum
 env GOPROXY=off
 go get -d rsc.io/quote@v1.5.2 # using cache
-rm $GOPATH/pkg/mod/download/cache/sumdb/localhost.localdev/sumdb/lookup/rsc.io/quote@v1.5.2
+rm $GOPATH/pkg/mod/cache/download/sumdb/localhost.localdev/sumdb/lookup/rsc.io/quote@v1.5.2
 go get -d rsc.io/quote@v1.5.2 # using go.sum
 
 # fetch fails once we lose access to both cache and go.sum

src/cmd/go/testdata/script/mod_sumdb_file_path.txt

@@ -2,6 +2,7 @@
 
 env GO111MODULE=on
 env GOSUMDB=
+env GOPATH=$WORK/gopath1
 
 # With a file-based proxy with an empty checksum directory,
 # downloading a new module should fail, even if a subsequent
@@ -18,11 +19,20 @@ stderr '^verifying golang.org/x/text.*: Not Found'
 [!windows] env GOPROXY=file://$WORK/emptyproxy,https://proxy.golang.org
 go get -d golang.org/x/text@v0.3.2
 
+# After a successful sumdb lookup, the lookup can be repeated
+# using the download cache as a proxy.
+cp supported $GOPATH/pkg/mod/cache/download/sumdb/sum.golang.org/supported
+[windows] env GOPROXY=file:///$WORK/gopath1/pkg/mod/cache/download,file:///$WORK/sumproxy
+[!windows] env GOPROXY=file://$WORK/gopath1/pkg/mod/cache/download,file://$WORK/sumproxy
+env GOPATH=$WORK/gopath2
+rm go.sum
+go get -d -x -v golang.org/x/text@v0.3.2
+
 # Once the checksum is present in the go.sum file,
 # an empty file-based sumdb can be used in conjunction with
 # a fallback module mirror.
 grep golang.org/x/text go.sum
-go clean -modcache
+env GOPATH=$WORK/gopath3
 [windows] env GOPROXY=file:///$WORK/sumproxy
 [!windows] env GOPROXY=file://$WORK/sumproxy
 ! go get -d golang.org/x/text@v0.3.2
@@ -30,6 +40,8 @@ go clean -modcache
 [!windows] env GOPROXY=file://$WORK/sumproxy,https://proxy.golang.org
 go get -d golang.org/x/text@v0.3.2
 
+-- supported --
+
 -- go.mod --
 module example.com
 go 1.13

src/cmd/go/testdata/script/mod_sumdb_proxy.txt

@@ -6,14 +6,14 @@ env GOPROXY GONOPROXY GOSUMDB GONOSUMDB
 # basic fetch (through proxy) works
 cp go.mod.orig go.mod
 go get -d rsc.io/fortune@v1.0.0 # note: must use test proxy, does not exist in real world
-rm $GOPATH/pkg/mod/download/cache/sumdb # rm sumdb cache but NOT package download cache
+rm $GOPATH/pkg/mod/cache/download/sumdb # rm sumdb cache but NOT package download cache
 rm go.sum
 
 # can fetch by explicit URL
 cp go.mod.orig go.mod
 env GOSUMDB=$sumdb' '$proxy/sumdb-direct
 go get -d rsc.io/fortune@v1.0.0
-rm $GOPATH/pkg/mod/download/cache/sumdb
+rm $GOPATH/pkg/mod/cache/download/sumdb
 rm go.sum
 
 # direct access fails (because localhost.localdev does not exist)
@@ -25,7 +25,7 @@ env GOSUMDB=$sumdb
 env GOPROXY=direct
 ! go get -d rsc.io/fortune@v1.0.0
 stderr 'verifying.*localhost.localdev'
-rm $GOPATH/pkg/mod/download/cache/sumdb
+rm $GOPATH/pkg/mod/cache/download/sumdb
 rm go.sum
 
 # proxy 404 falls back to direct access (which fails)
@@ -34,7 +34,7 @@ env GOSUMDB=$sumdb
 env GOPROXY=$proxy/sumdb-404
 ! go get -d rsc.io/fortune@v1.0.0
 stderr 'verifying.*localhost.localdev'
-rm $GOPATH/pkg/mod/download/cache/sumdb
+rm $GOPATH/pkg/mod/cache/download/sumdb
 rm go.sum
 
 # proxy non-200/404/410 stops direct access
@@ -43,7 +43,7 @@ env GOSUMDB=$sumdb
 env GOPROXY=$proxy/sumdb-503
 ! go get -d rsc.io/fortune@v1.0.0
 stderr '503 Service Unavailable'
-rm $GOPATH/pkg/mod/download/cache/sumdb
+rm $GOPATH/pkg/mod/cache/download/sumdb
 rm go.sum
 
 -- go.mod.orig --