From 6b0929505ba7d4ede45d587239459d3f2eb8c3d4 Mon Sep 17 00:00:00 2001
From: Russ Cox <rsc@golang.org>
Date: Tue, 27 Mar 2012 10:41:44 -0400
Subject: [PATCH] cmd/go: fix two bugs

Issue 3207 was caused by setting GOPATH=GOROOT.
This is a common mistake, so diagnose it at command start
and also correct the bug that it caused in get (downloading
to GOROOT/src/foo instead of GOROOT/src/pkg/foo).

Issue 3268 was caused by recognizing 'packages' that
had installed binaries but no source.  This behavior is not
documented and causes trouble, so remove it.  We can
revisit the concept of binary-only packages after Go 1.

Fixes #3207.
Fixes #3268.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/5930044
---
 src/cmd/go/get.go  | 4 +++-
 src/cmd/go/main.go | 8 ++++++++
 src/cmd/go/pkg.go  | 5 ++++-
 3 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/src/cmd/go/get.go b/src/cmd/go/get.go
index 6ad683a8be..f70b6761de 100644
--- a/src/cmd/go/get.go
+++ b/src/cmd/go/get.go
@@ -252,7 +252,9 @@ func downloadPackage(p *Package) error {
 
 	if p.build.SrcRoot == "" {
 		// Package not found.  Put in first directory of $GOPATH or else $GOROOT.
-		if list := filepath.SplitList(buildContext.GOPATH); len(list) > 0 {
+		// Guard against people setting GOPATH=$GOROOT.  We have to use
+		// $GOROOT's directory hierarchy (src/pkg, not just src) in that case.
+		if list := filepath.SplitList(buildContext.GOPATH); len(list) > 0 && list[0] != goroot {
 			p.build.SrcRoot = filepath.Join(list[0], "src")
 			p.build.PkgRoot = filepath.Join(list[0], "pkg")
 		} else {
diff --git a/src/cmd/go/main.go b/src/cmd/go/main.go
index 2f8209c86f..73c2f54a76 100644
--- a/src/cmd/go/main.go
+++ b/src/cmd/go/main.go
@@ -16,6 +16,7 @@ import (
 	"path"
 	"path/filepath"
 	"regexp"
+	"runtime"
 	"strings"
 	"sync"
 	"text/template"
@@ -121,6 +122,13 @@ func main() {
 		return
 	}
 
+	// Diagnose common mistake: GOPATH==GOROOT.
+	// This setting is equivalent to not setting GOPATH at all,
+	// which is not what most people want when they do it.
+	if gopath := os.Getenv("GOPATH"); gopath == runtime.GOROOT() {
+		fmt.Fprintf(os.Stderr, "warning: GOPATH set to GOROOT (%s) has no effect\n", gopath)
+	}
+
 	for _, cmd := range commands {
 		if cmd.Name() == args[0] && cmd.Run != nil {
 			cmd.Flag.Usage = func() { cmd.Usage() }
diff --git a/src/cmd/go/pkg.go b/src/cmd/go/pkg.go
index 44dbd6798a..1a75019aca 100644
--- a/src/cmd/go/pkg.go
+++ b/src/cmd/go/pkg.go
@@ -217,7 +217,10 @@ func loadImport(path string, srcDir string, stk *importStack, importPos []token.
 	// Load package.
 	// Import always returns bp != nil, even if an error occurs,
 	// in order to return partial information.
-	bp, err := buildContext.Import(path, srcDir, build.AllowBinary)
+	//
+	// TODO: After Go 1, decide when to pass build.AllowBinary here.
+	// See issue 3268 for mistakes to avoid.
+	bp, err := buildContext.Import(path, srcDir, 0)
 	bp.ImportPath = importPath
 	p.load(stk, bp, err)
 	if p.Error != nil && len(importPos) > 0 {