1 files changed, 23 insertions, 6 deletions

diff --git a/libgo/go/cmd/go/internal/web/http.go b/libgo/go/cmd/go/internal/web/http.go
index b790fe9916e..5e4319b00e9 100644
--- a/libgo/go/cmd/go/internal/web/http.go
+++ b/libgo/go/cmd/go/internal/web/http.go
@@ -14,7 +14,7 @@ package web
 import (
 	"crypto/tls"
 	"fmt"
-	"io/ioutil"
+	"mime"
 	"net/http"
 	urlpkg "net/url"
 	"os"
@@ -64,7 +64,7 @@ func get(security SecurityMode, url *urlpkg.URL) (*Response, error) {
 			Status:     "404 testing",
 			StatusCode: 404,
 			Header:     make(map[string][]string),
-			Body:       ioutil.NopCloser(strings.NewReader("")),
+			Body:       http.NoBody,
 		}
 		if cfg.BuildX {
 			fmt.Fprintf(os.Stderr, "# get %s: %v (%.3fs)\n", Redacted(url), res.Status, time.Since(start).Seconds())
@@ -111,7 +111,7 @@ func get(security SecurityMode, url *urlpkg.URL) (*Response, error) {
 		fetched, res, err = fetch(secure)
 		if err != nil {
 			if cfg.BuildX {
-				fmt.Fprintf(os.Stderr, "# get %s: %v\n", Redacted(url), err)
+				fmt.Fprintf(os.Stderr, "# get %s: %v\n", Redacted(secure), err)
 			}
 			if security != Insecure || url.Scheme == "https" {
 				// HTTPS failed, and we can't fall back to plain HTTP.
@@ -146,7 +146,7 @@ func get(security SecurityMode, url *urlpkg.URL) (*Response, error) {
 		insecure.Scheme = "http"
 		if insecure.User != nil && security != Insecure {
 			if cfg.BuildX {
-				fmt.Fprintf(os.Stderr, "# get %s: insecure credentials\n", Redacted(url))
+				fmt.Fprintf(os.Stderr, "# get %s: insecure credentials\n", Redacted(insecure))
 			}
 			return nil, fmt.Errorf("refusing to pass credentials to insecure URL: %s", Redacted(insecure))
 		}
@@ -154,7 +154,7 @@ func get(security SecurityMode, url *urlpkg.URL) (*Response, error) {
 		fetched, res, err = fetch(insecure)
 		if err != nil {
 			if cfg.BuildX {
-				fmt.Fprintf(os.Stderr, "# get %s: %v\n", Redacted(url), err)
+				fmt.Fprintf(os.Stderr, "# get %s: %v\n", Redacted(insecure), err)
 			}
 			// HTTP failed, and we already tried HTTPS if applicable.
 			// Report the error from the HTTP attempt.
@@ -165,8 +165,9 @@ func get(security SecurityMode, url *urlpkg.URL) (*Response, error) {
 	// Note: accepting a non-200 OK here, so people can serve a
 	// meta import in their http 404 page.
 	if cfg.BuildX {
-		fmt.Fprintf(os.Stderr, "# get %s: %v (%.3fs)\n", Redacted(url), res.Status, time.Since(start).Seconds())
+		fmt.Fprintf(os.Stderr, "# get %s: %v (%.3fs)\n", Redacted(fetched), res.Status, time.Since(start).Seconds())
 	}
+
 	r := &Response{
 		URL:        Redacted(fetched),
 		Status:     res.Status,
@@ -174,6 +175,20 @@ func get(security SecurityMode, url *urlpkg.URL) (*Response, error) {
 		Header:     map[string][]string(res.Header),
 		Body:       res.Body,
 	}
+
+	if res.StatusCode != http.StatusOK {
+		contentType := res.Header.Get("Content-Type")
+		if mediaType, params, _ := mime.ParseMediaType(contentType); mediaType == "text/plain" {
+			switch charset := strings.ToLower(params["charset"]); charset {
+			case "us-ascii", "utf-8", "":
+				// Body claims to be plain text in UTF-8 or a subset thereof.
+				// Try to extract a useful error message from it.
+				r.errorDetail.r = res.Body
+				r.Body = &r.errorDetail
+			}
+		}
+	}
+
 	return r, nil
 }
 
@@ -190,6 +205,7 @@ func getFile(u *urlpkg.URL) (*Response, error) {
 			Status:     http.StatusText(http.StatusNotFound),
 			StatusCode: http.StatusNotFound,
 			Body:       http.NoBody,
+			fileErr:    err,
 		}, nil
 	}
 
@@ -199,6 +215,7 @@ func getFile(u *urlpkg.URL) (*Response, error) {
 			Status:     http.StatusText(http.StatusForbidden),
 			StatusCode: http.StatusForbidden,
 			Body:       http.NoBody,
+			fileErr:    err,
 		}, nil
 	}