1 files changed, 48 insertions, 0 deletions
diff --git a/src/cmd/go/internal/work/testgo.go b/src/cmd/go/internal/work/testgo.go
new file mode 100644
index 0000000..931f49a
--- /dev/null
+++ b/src/cmd/go/internal/work/testgo.go
@@ -0,0 +1,48 @@
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file contains extra hooks for testing the go command.
+
+// +build testgo
+
+package work
+
+import (
+	"cmd/go/internal/cfg"
+	"cmd/go/internal/search"
+	"fmt"
+	"os"
+	"path/filepath"
+	"runtime"
+)
+
+func init() {
+	if v := os.Getenv("TESTGO_VERSION"); v != "" {
+		runtimeVersion = v
+	}
+
+	if testGOROOT := os.Getenv("TESTGO_GOROOT"); testGOROOT != "" {
+		// Disallow installs to the GOROOT from which testgo was built.
+		// Installs to other GOROOTs — such as one set explicitly within a test — are ok.
+		allowInstall = func(a *Action) error {
+			if cfg.BuildN {
+				return nil
+			}
+
+			rel := search.InDir(a.Target, testGOROOT)
+			if rel == "" {
+				return nil
+			}
+
+			callerPos := ""
+			if _, file, line, ok := runtime.Caller(1); ok {
+				if shortFile := search.InDir(file, filepath.Join(testGOROOT, "src")); shortFile != "" {
+					file = shortFile
+				}
+				callerPos = fmt.Sprintf("%s:%d: ", file, line)
+			}
+			return fmt.Errorf("%stestgo must not write to GOROOT (installing to %s)", callerPos, filepath.Join("GOROOT", rel))
+		}
+	}
+}