cmd/go: rank errUseProxy lower when handling proxy errors

modfetch.TryProxies ranks errors returned by GOPROXY entries by
usefulness. It returns the error of the highest rank from the last
proxy. Errors from "direct" and "noproxy" are most useful, followed by
errors other than ErrNotExist, followed by ErrNotExist.

This change ranks errUseProxy with ErrNotExist even though it's
reported by "noproxy". There is almost always a more useful message
than "path does not match GOPRIVATE/GONOPROXY".

Fixes #39180

Change-Id: Ifa5b96462d7bf411e6d2d951888465c839d42471
Reviewed-on: https://go-review.googlesource.com/c/go/+/234687
Run-TryBot: Jay Conrod <jayconrod@google.com>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

diff --git a/src/cmd/go/internal/modfetch/proxy.go b/src/cmd/go/internal/modfetch/proxy.go
index 0ca43d4c4a4f57d1944abcb3ec6823bcf1dd3f98..3971598733f4bc12833580fb53b7ae68f45da008 100644 (file)
--- a/src/cmd/go/internal/modfetch/proxy.go
+++ b/src/cmd/go/internal/modfetch/proxy.go
@@ -196,8 +196,12 @@ func TryProxies(f func(proxy string) error) error {
 
        // We try to report the most helpful error to the user. "direct" and "noproxy"
        // errors are best, followed by proxy errors other than ErrNotExist, followed
-       // by ErrNotExist. Note that errProxyOff, errNoproxy, and errUseProxy are
-       // equivalent to ErrNotExist.
+       // by ErrNotExist.
+       //
+       // Note that errProxyOff, errNoproxy, and errUseProxy are equivalent to
+       // ErrNotExist. errUseProxy should only be returned if "noproxy" is the only
+       // proxy. errNoproxy should never be returned, since there should always be a
+       // more useful error from "noproxy" first.
        const (
                notExistRank = iota
                proxyRank
@@ -212,7 +216,7 @@ func TryProxies(f func(proxy string) error) error {
                }
                isNotExistErr := errors.Is(err, os.ErrNotExist)
 
-               if proxy.url == "direct" || proxy.url == "noproxy" {
+               if proxy.url == "direct" || (proxy.url == "noproxy" && err != errUseProxy) {
                        bestErr = err
                        bestErrRank = directRank
                } else if bestErrRank <= proxyRank && !isNotExistErr {

diff --git a/src/cmd/go/testdata/script/mod_gonoproxy.txt b/src/cmd/go/testdata/script/mod_gonoproxy.txt
index 2bd94cdee0428bcdb30acd7e48376c4a6be7dd82..d7848c7d263e7d17de1ba2c3f9b7882f144f2f3f 100644 (file)
--- a/src/cmd/go/testdata/script/mod_gonoproxy.txt
+++ b/src/cmd/go/testdata/script/mod_gonoproxy.txt
@@ -10,7 +10,7 @@ env GOSUMDB=$sumdb' '$proxy/sumdb-wrong
 ! go get rsc.io/quote
 stderr 'SECURITY ERROR'
 
-# but GONOSUMDB bypasses sumdb, for rsc.io/quote, rsc.io/sampler, golang.org/x/text
+# GONOSUMDB bypasses sumdb, for rsc.io/quote, rsc.io/sampler, golang.org/x/text
 env GONOSUMDB='*/quote,*/*mple*,golang.org/x'
 go get rsc.io/quote
 rm go.sum
@@ -18,7 +18,13 @@ env GOPRIVATE='*/quote,*/*mple*,golang.org/x'
 env GONOPROXY=none # that is, proxy all despite GOPRIVATE
 go get rsc.io/quote
 
-# and GONOPROXY bypasses proxy
+# When GOPROXY=off, fetching modules not matched by GONOPROXY fails.
+env GONOPROXY=*/fortune
+env GOPROXY=off
+! go get golang.org/x/text
+stderr '^go get golang.org/x/text: module lookup disabled by GOPROXY=off$'
+
+# GONOPROXY bypasses proxy
 [!net] skip
 [!exec:git] skip
 env GOPRIVATE=none