[release-branch.go1.17] cmd/dist: consistently set PWD when executing a command in a different directory

Fixes #52995
Updates #33598

Change-Id: If0de906ffa2fcc83bb2a90f9e80a5b29d7667398
Reviewed-on: https://go-review.googlesource.com/c/go/+/353449
Trust: Bryan C. Mills <bcmills@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
(cherry picked from commit c035d829e9fbd150148a1738020fe9c155cda61f)
Reviewed-on: https://go-review.googlesource.com/c/go/+/407881
Reviewed-by: Heschi Kreinick <heschi@google.com>
Run-TryBot: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

3 files changed, 80 insertions, 29 deletions

diff --git a/src/cmd/dist/exec.go b/src/cmd/dist/exec.go
new file mode 100644
index 0000000000..67305530ae
--- /dev/null
+++ b/src/cmd/dist/exec.go
@@ -0,0 +1,53 @@
+// Copyright 2021 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.
+
+package main
+
+import (
+	"os"
+	"os/exec"
+	"strings"
+)
+
+// setDir sets cmd.Dir to dir, and also adds PWD=dir to cmd's environment.
+func setDir(cmd *exec.Cmd, dir string) {
+	cmd.Dir = dir
+	setEnv(cmd, "PWD", dir)
+}
+
+// setEnv sets cmd.Env so that key = value.
+//
+// It first removes any existing values for key, so it is safe to call
+// even from within cmdbootstrap.
+func setEnv(cmd *exec.Cmd, key, value string) {
+	kv := key + "=" + value
+	if cmd.Env == nil {
+		cmd.Env = os.Environ()
+	}
+
+	prefix := kv[:len(key)+1]
+	for i, entry := range cmd.Env {
+		if strings.HasPrefix(entry, prefix) {
+			cmd.Env[i] = kv
+			return
+		}
+	}
+
+	cmd.Env = append(cmd.Env, kv)
+}
+
+// unsetEnv sets cmd.Env so that key is not present in the environment.
+func unsetEnv(cmd *exec.Cmd, key string) {
+	if cmd.Env == nil {
+		cmd.Env = os.Environ()
+	}
+
+	prefix := key + "="
+	for i, entry := range cmd.Env {
+		if strings.HasPrefix(entry, prefix) {
+			cmd.Env = append(cmd.Env[:i], cmd.Env[i+1:]...)
+			return
+		}
+	}
+}
diff --git a/src/cmd/dist/test.go b/src/cmd/dist/test.go
index f40fa926df..beb7c4650c 100644
--- a/src/cmd/dist/test.go
+++ b/src/cmd/dist/test.go
@@ -522,7 +522,8 @@ func (t *tester) registerTests() {
 			heading: "GOOS=ios on darwin/amd64",
 			fn: func(dt *distTest) error {
 				cmd := t.addCmd(dt, "src", t.goTest(), t.timeout(300), "-run=SystemRoots", "crypto/x509")
-				cmd.Env = append(os.Environ(), "GOOS=ios", "CGO_ENABLED=1")
+				setEnv(cmd, "GOOS", "ios")
+				setEnv(cmd, "CGO_ENABLED", "1")
 				return nil
 			},
 		})
@@ -542,7 +543,7 @@ func (t *tester) registerTests() {
 				cmd := t.addCmd(dt, "src", t.goTest(), t.timeout(300), "runtime", "-cpu=1,2,4", "-quick")
 				// We set GOMAXPROCS=2 in addition to -cpu=1,2,4 in order to test runtime bootstrap code,
 				// creation of first goroutines and first garbage collections in the parallel setting.
-				cmd.Env = append(os.Environ(), "GOMAXPROCS=2")
+				setEnv(cmd, "GOMAXPROCS", "2")
 				return nil
 			},
 		})
@@ -563,7 +564,7 @@ func (t *tester) registerTests() {
 					return nil
 				}
 				cmd := exec.Command("go", "test")
-				cmd.Dir = filepath.Join(os.Getenv("GOROOT"), "src/cmd/go/testdata/testterminal18153")
+				setDir(cmd, filepath.Join(os.Getenv("GOROOT"), "src/cmd/go/testdata/testterminal18153"))
 				cmd.Stdout = os.Stdout
 				cmd.Stderr = os.Stderr
 				return cmd.Run()
@@ -600,16 +601,13 @@ func (t *tester) registerTests() {
 					return err
 				}
 
-				// Run `go test fmt` in the moved GOROOT.
+				// Run `go test fmt` in the moved GOROOT, without explicitly setting
+				// GOROOT in the environment. The 'go' command should find itself.
 				cmd := exec.Command(filepath.Join(moved, "bin", "go"), "test", "fmt")
 				cmd.Stdout = os.Stdout
 				cmd.Stderr = os.Stderr
-				// Don't set GOROOT in the environment.
-				for _, e := range os.Environ() {
-					if !strings.HasPrefix(e, "GOROOT=") && !strings.HasPrefix(e, "GOCACHE=") {
-						cmd.Env = append(cmd.Env, e)
-					}
-				}
+				unsetEnv(cmd, "GOROOT")
+				unsetEnv(cmd, "GOCACHE") // TODO(bcmills): ...why‽
 				err := cmd.Run()
 
 				if rerr := os.Rename(moved, goroot); rerr != nil {
@@ -736,11 +734,9 @@ func (t *tester) registerTests() {
 						heading: "../misc/swig/callback",
 						fn: func(dt *distTest) error {
 							cmd := t.addCmd(dt, "misc/swig/callback", t.goTest())
-							cmd.Env = append(os.Environ(),
-								"CGO_CFLAGS=-flto -Wno-lto-type-mismatch -Wno-unknown-warning-option",
-								"CGO_CXXFLAGS=-flto -Wno-lto-type-mismatch -Wno-unknown-warning-option",
-								"CGO_LDFLAGS=-flto -Wno-lto-type-mismatch -Wno-unknown-warning-option",
-							)
+							setEnv(cmd, "CGO_CFLAGS", "-flto -Wno-lto-type-mismatch -Wno-unknown-warning-option")
+							setEnv(cmd, "CGO_CXXFLAGS", "-flto -Wno-lto-type-mismatch -Wno-unknown-warning-option")
+							setEnv(cmd, "CGO_LDFLAGS", "-flto -Wno-lto-type-mismatch -Wno-unknown-warning-option")
 							return nil
 						},
 					},
@@ -892,9 +888,9 @@ func (t *tester) registerSeqTest(name, dirBanner string, cmdline ...interface{})
 func (t *tester) bgDirCmd(dir, bin string, args ...string) *exec.Cmd {
 	cmd := exec.Command(bin, args...)
 	if filepath.IsAbs(dir) {
-		cmd.Dir = dir
+		setDir(cmd, dir)
 	} else {
-		cmd.Dir = filepath.Join(goroot, dir)
+		setDir(cmd, filepath.Join(goroot, dir))
 	}
 	return cmd
 }
@@ -1132,7 +1128,8 @@ func (t *tester) runHostTest(dir, pkg string) error {
 	defer os.Remove(f.Name())
 
 	cmd := t.dirCmd(dir, t.goTest(), "-c", "-o", f.Name(), pkg)
-	cmd.Env = append(os.Environ(), "GOARCH="+gohostarch, "GOOS="+gohostos)
+	setEnv(cmd, "GOARCH", gohostarch)
+	setEnv(cmd, "GOOS", gohostos)
 	if err := cmd.Run(); err != nil {
 		return err
 	}
@@ -1141,7 +1138,7 @@ func (t *tester) runHostTest(dir, pkg string) error {
 
 func (t *tester) cgoTest(dt *distTest) error {
 	cmd := t.addCmd(dt, "misc/cgo/test", t.goTest())
-	cmd.Env = append(os.Environ(), "GOFLAGS=-ldflags=-linkmode=auto")
+	setEnv(cmd, "GOFLAGS", "-ldflags=-linkmode=auto")
 
 	// Skip internal linking cases on linux/arm64 to support GCC-9.4 and above.
 	// See issue #39466.
@@ -1149,7 +1146,7 @@ func (t *tester) cgoTest(dt *distTest) error {
 
 	if t.internalLink() && !skipInternalLink {
 		cmd := t.addCmd(dt, "misc/cgo/test", t.goTest(), "-tags=internal")
-		cmd.Env = append(os.Environ(), "GOFLAGS=-ldflags=-linkmode=internal")
+		setEnv(cmd, "GOFLAGS", "-ldflags=-linkmode=internal")
 	}
 
 	pair := gohostos + "-" + goarch
@@ -1161,9 +1158,9 @@ func (t *tester) cgoTest(dt *distTest) error {
 			break
 		}
 		cmd := t.addCmd(dt, "misc/cgo/test", t.goTest())
-		cmd.Env = append(os.Environ(), "GOFLAGS=-ldflags=-linkmode=external")
+		setEnv(cmd, "GOFLAGS", "-ldflags=-linkmode=external")
 
-		cmd = t.addCmd(dt, "misc/cgo/test", t.goTest(), "-ldflags", "-linkmode=external -s")
+		t.addCmd(dt, "misc/cgo/test", t.goTest(), "-ldflags", "-linkmode=external -s")
 
 		if t.supportedBuildmode("pie") {
 			t.addCmd(dt, "misc/cgo/test", t.goTest(), "-buildmode=pie")
@@ -1181,10 +1178,10 @@ func (t *tester) cgoTest(dt *distTest) error {
 		"openbsd-386", "openbsd-amd64", "openbsd-arm", "openbsd-arm64", "openbsd-mips64":
 
 		cmd := t.addCmd(dt, "misc/cgo/test", t.goTest())
-		cmd.Env = append(os.Environ(), "GOFLAGS=-ldflags=-linkmode=external")
+		setEnv(cmd, "GOFLAGS", "-ldflags=-linkmode=external")
 		// cgo should be able to cope with both -g arguments and colored
 		// diagnostics.
-		cmd.Env = append(cmd.Env, "CGO_CFLAGS=-g0 -fdiagnostics-color")
+		setEnv(cmd, "CGO_CFLAGS", "-g0 -fdiagnostics-color")
 
 		t.addCmd(dt, "misc/cgo/testtls", t.goTest(), "-ldflags", "-linkmode=auto")
 		t.addCmd(dt, "misc/cgo/testtls", t.goTest(), "-ldflags", "-linkmode=external")
@@ -1217,7 +1214,7 @@ func (t *tester) cgoTest(dt *distTest) error {
 					// than -static in -extldflags, so test both.
 					// See issue #16651.
 					cmd := t.addCmd(dt, "misc/cgo/test", t.goTest(), "-tags=static")
-					cmd.Env = append(os.Environ(), "CGO_LDFLAGS=-static -pthread")
+					setEnv(cmd, "CGO_LDFLAGS", "-static -pthread")
 				}
 			}
 
@@ -1456,7 +1453,7 @@ func (t *tester) raceTest(dt *distTest) error {
 		// We shouldn't need to redo all of misc/cgo/test too.
 		// The race buildler will take care of this.
 		// cmd := t.addCmd(dt, "misc/cgo/test", t.goTest(), "-race")
-		// cmd.Env = append(os.Environ(), "GOTRACEBACK=2")
+		// setEnv(cmd, "GOTRACEBACK", "2")
 	}
 	if t.extLink() {
 		// Test with external linking; see issue 9133.
@@ -1486,7 +1483,8 @@ func (t *tester) testDirTest(dt *distTest, shard, shards int) error {
 		})
 
 		cmd := t.dirCmd("test", "go", "build", "-o", runtest.exe, "run.go")
-		cmd.Env = append(os.Environ(), "GOOS="+gohostos, "GOARCH="+gohostarch)
+		setEnv(cmd, "GOOS", gohostos)
+		setEnv(cmd, "GOARCH", gohostarch)
 		runtest.err = cmd.Run()
 	})
 	if runtest.err != nil {
@@ -1650,7 +1648,7 @@ func (t *tester) runPrecompiledStdTest(timeout time.Duration) error {
 	bin := t.prebuiltGoPackageTestBinary()
 	fmt.Fprintf(os.Stderr, "# %s: using pre-built %s...\n", stdMatches[0], bin)
 	cmd := exec.Command(bin, "-test.short="+short(), "-test.timeout="+timeout.String())
-	cmd.Dir = filepath.Dir(bin)
+	setDir(cmd, filepath.Dir(bin))
 	cmd.Stdout = os.Stdout
 	cmd.Stderr = os.Stderr
 	if err := cmd.Start(); err != nil {
diff --git a/src/cmd/dist/util.go b/src/cmd/dist/util.go
index df60145d1e..28fe5e1d8d 100644
--- a/src/cmd/dist/util.go
+++ b/src/cmd/dist/util.go
@@ -72,7 +72,7 @@ func run(dir string, mode int, cmd ...string) string {
 	}
 
 	xcmd := exec.Command(cmd[0], cmd[1:]...)
-	xcmd.Dir = dir
+	setDir(xcmd, dir)
 	var data []byte
 	var err error