os/exec: return error when PATH lookup would use current directory

CL 381374 was reverted because x/sys/execabs broke.

This CL reapplies CL 381374, but adding a lookPathErr error
field back, for execabs to manipulate with reflect.
That field will just be a bit of scar tissue in this package forever,
to keep old code working with new toolchains.

CL 403256 fixes x/sys/execabs's test to be ready for the change.
Older versions of x/sys/execabs will keep working
(that is, will keep rejecting what they should reject),
but they will return a slightly different error from LookPath
without that CL, and the test fails because of the different
error text.

For #43724.

This reverts commit f2b674756b3b684118e4245627d4ed8c07e518e7.

Change-Id: Iee55f8cd9939e1bd31e5cbdada50681cdc505117
Reviewed-on: https://go-review.googlesource.com/c/go/+/403274
Auto-Submit: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>

1 files changed, 0 insertions, 103 deletions

diff --git a/src/internal/execabs/execabs_test.go b/src/internal/execabs/execabs_test.go
deleted file mode 100644
index 97a3f39b4a..0000000000
--- a/src/internal/execabs/execabs_test.go
+++ /dev/null
@@ -1,103 +0,0 @@
-// Copyright 2020 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 execabs
-
-import (
-	"context"
-	"fmt"
-	"internal/testenv"
-	"os"
-	"os/exec"
-	"path/filepath"
-	"runtime"
-	"testing"
-)
-
-func TestFixCmd(t *testing.T) {
-	cmd := &exec.Cmd{Path: "hello"}
-	fixCmd("hello", cmd)
-	if cmd.Path != "" {
-		t.Error("fixCmd didn't clear cmd.Path")
-	}
-	expectedErr := fmt.Sprintf("hello resolves to executable relative to current directory (.%chello)", filepath.Separator)
-	if err := cmd.Run(); err == nil {
-		t.Fatal("Command.Run didn't fail")
-	} else if err.Error() != expectedErr {
-		t.Fatalf("Command.Run returned unexpected error: want %q, got %q", expectedErr, err.Error())
-	}
-}
-
-func TestCommand(t *testing.T) {
-	testenv.MustHaveExec(t)
-
-	for _, cmd := range []func(string) *Cmd{
-		func(s string) *Cmd { return Command(s) },
-		func(s string) *Cmd { return CommandContext(context.Background(), s) },
-	} {
-		tmpDir := t.TempDir()
-		executable := "execabs-test"
-		if runtime.GOOS == "windows" {
-			executable += ".exe"
-		}
-		if err := os.WriteFile(filepath.Join(tmpDir, executable), []byte{1, 2, 3}, 0111); err != nil {
-			t.Fatalf("os.WriteFile failed: %s", err)
-		}
-		cwd, err := os.Getwd()
-		if err != nil {
-			t.Fatalf("os.Getwd failed: %s", err)
-		}
-		defer os.Chdir(cwd)
-		if err = os.Chdir(tmpDir); err != nil {
-			t.Fatalf("os.Chdir failed: %s", err)
-		}
-		if runtime.GOOS != "windows" {
-			// add "." to PATH so that exec.LookPath looks in the current directory on
-			// non-windows platforms as well
-			origPath := os.Getenv("PATH")
-			defer os.Setenv("PATH", origPath)
-			os.Setenv("PATH", fmt.Sprintf(".:%s", origPath))
-		}
-		expectedErr := fmt.Sprintf("execabs-test resolves to executable relative to current directory (.%c%s)", filepath.Separator, executable)
-		if err = cmd("execabs-test").Run(); err == nil {
-			t.Fatalf("Command.Run didn't fail when exec.LookPath returned a relative path")
-		} else if err.Error() != expectedErr {
-			t.Errorf("Command.Run returned unexpected error: want %q, got %q", expectedErr, err.Error())
-		}
-	}
-}
-
-func TestLookPath(t *testing.T) {
-	testenv.MustHaveExec(t)
-
-	tmpDir := t.TempDir()
-	executable := "execabs-test"
-	if runtime.GOOS == "windows" {
-		executable += ".exe"
-	}
-	if err := os.WriteFile(filepath.Join(tmpDir, executable), []byte{1, 2, 3}, 0111); err != nil {
-		t.Fatalf("os.WriteFile failed: %s", err)
-	}
-	cwd, err := os.Getwd()
-	if err != nil {
-		t.Fatalf("os.Getwd failed: %s", err)
-	}
-	defer os.Chdir(cwd)
-	if err = os.Chdir(tmpDir); err != nil {
-		t.Fatalf("os.Chdir failed: %s", err)
-	}
-	if runtime.GOOS != "windows" {
-		// add "." to PATH so that exec.LookPath looks in the current directory on
-		// non-windows platforms as well
-		origPath := os.Getenv("PATH")
-		defer os.Setenv("PATH", origPath)
-		os.Setenv("PATH", fmt.Sprintf(".:%s", origPath))
-	}
-	expectedErr := fmt.Sprintf("execabs-test resolves to executable relative to current directory (.%c%s)", filepath.Separator, executable)
-	if _, err := LookPath("execabs-test"); err == nil {
-		t.Fatalf("LookPath didn't fail when finding a non-relative path")
-	} else if err.Error() != expectedErr {
-		t.Errorf("LookPath returned unexpected error: want %q, got %q", expectedErr, err.Error())
-	}
-}