1 files changed, 192 insertions, 0 deletions
diff --git a/src/os/exec/dot_test.go b/src/os/exec/dot_test.go
new file mode 100644
index 0000000..66c92f7
--- /dev/null
+++ b/src/os/exec/dot_test.go
@@ -0,0 +1,192 @@
+// Copyright 2022 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 exec_test
+
+import (
+	"errors"
+	"internal/testenv"
+	"os"
+	. "os/exec"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"testing"
+)
+
+var pathVar string = func() string {
+	if runtime.GOOS == "plan9" {
+		return "path"
+	}
+	return "PATH"
+}()
+
+func TestLookPath(t *testing.T) {
+	testenv.MustHaveExec(t)
+	// Not parallel: uses os.Chdir and t.Setenv.
+
+	tmpDir := filepath.Join(t.TempDir(), "testdir")
+	if err := os.Mkdir(tmpDir, 0777); err != nil {
+		t.Fatal(err)
+	}
+
+	executable := "execabs-test"
+	if runtime.GOOS == "windows" {
+		executable += ".exe"
+	}
+	if err := os.WriteFile(filepath.Join(tmpDir, executable), []byte{1, 2, 3}, 0777); err != nil {
+		t.Fatal(err)
+	}
+	cwd, err := os.Getwd()
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer func() {
+		if err := os.Chdir(cwd); err != nil {
+			panic(err)
+		}
+	}()
+	if err = os.Chdir(tmpDir); err != nil {
+		t.Fatal(err)
+	}
+	t.Setenv("PWD", tmpDir)
+	t.Logf(". is %#q", tmpDir)
+
+	origPath := os.Getenv(pathVar)
+
+	// Add "." to PATH so that exec.LookPath looks in the current directory on all systems.
+	// And try to trick it with "../testdir" too.
+	for _, errdot := range []string{"1", "0"} {
+		t.Run("GODEBUG=execerrdot="+errdot, func(t *testing.T) {
+			t.Setenv("GODEBUG", "execerrdot="+errdot+",execwait=2")
+			for _, dir := range []string{".", "../testdir"} {
+				t.Run(pathVar+"="+dir, func(t *testing.T) {
+					t.Setenv(pathVar, dir+string(filepath.ListSeparator)+origPath)
+					good := dir + "/execabs-test"
+					if found, err := LookPath(good); err != nil || !strings.HasPrefix(found, good) {
+						t.Fatalf(`LookPath(%#q) = %#q, %v, want "%s...", nil`, good, found, err, good)
+					}
+					if runtime.GOOS == "windows" {
+						good = dir + `\execabs-test`
+						if found, err := LookPath(good); err != nil || !strings.HasPrefix(found, good) {
+							t.Fatalf(`LookPath(%#q) = %#q, %v, want "%s...", nil`, good, found, err, good)
+						}
+					}
+
+					_, err := LookPath("execabs-test")
+					if errdot == "1" {
+						if err == nil {
+							t.Fatalf("LookPath didn't fail when finding a non-relative path")
+						} else if !errors.Is(err, ErrDot) {
+							t.Fatalf("LookPath returned unexpected error: want Is ErrDot, got %q", err)
+						}
+					} else {
+						if err != nil {
+							t.Fatalf("LookPath failed unexpectedly: %v", err)
+						}
+					}
+
+					cmd := Command("execabs-test")
+					if errdot == "1" {
+						if cmd.Err == nil {
+							t.Fatalf("Command didn't fail when finding a non-relative path")
+						} else if !errors.Is(cmd.Err, ErrDot) {
+							t.Fatalf("Command returned unexpected error: want Is ErrDot, got %q", cmd.Err)
+						}
+						cmd.Err = nil
+					} else {
+						if cmd.Err != nil {
+							t.Fatalf("Command failed unexpectedly: %v", err)
+						}
+					}
+
+					// Clearing cmd.Err should let the execution proceed,
+					// and it should fail because it's not a valid binary.
+					if err := cmd.Run(); err == nil {
+						t.Fatalf("Run did not fail: expected exec error")
+					} else if errors.Is(err, ErrDot) {
+						t.Fatalf("Run returned unexpected error ErrDot: want error like ENOEXEC: %q", err)
+					}
+				})
+			}
+		})
+	}
+
+	// Test the behavior when the first entry in PATH is an absolute name for the
+	// current directory.
+	//
+	// On Windows, "." may or may not be implicitly included before the explicit
+	// %PATH%, depending on the process environment;
+	// see https://go.dev/issue/4394.
+	//
+	// If the relative entry from "." resolves to the same executable as what
+	// would be resolved from an absolute entry in %PATH% alone, LookPath should
+	// return the absolute version of the path instead of ErrDot.
+	// (See https://go.dev/issue/53536.)
+	//
+	// If PATH does not implicitly include "." (such as on Unix platforms, or on
+	// Windows configured with NoDefaultCurrentDirectoryInExePath), then this
+	// lookup should succeed regardless of the behavior for ".", so it may be
+	// useful to run as a control case even on those platforms.
+	t.Run(pathVar+"=$PWD", func(t *testing.T) {
+		t.Setenv(pathVar, tmpDir+string(filepath.ListSeparator)+origPath)
+		good := filepath.Join(tmpDir, "execabs-test")
+		if found, err := LookPath(good); err != nil || !strings.HasPrefix(found, good) {
+			t.Fatalf(`LookPath(%#q) = %#q, %v, want \"%s...\", nil`, good, found, err, good)
+		}
+
+		if found, err := LookPath("execabs-test"); err != nil || !strings.HasPrefix(found, good) {
+			t.Fatalf(`LookPath(%#q) = %#q, %v, want \"%s...\", nil`, "execabs-test", found, err, good)
+		}
+
+		cmd := Command("execabs-test")
+		if cmd.Err != nil {
+			t.Fatalf("Command(%#q).Err = %v; want nil", "execabs-test", cmd.Err)
+		}
+	})
+
+	t.Run(pathVar+"=$OTHER", func(t *testing.T) {
+		// Control case: if the lookup returns ErrDot when PATH is empty, then we
+		// know that PATH implicitly includes ".". If it does not, then we don't
+		// expect to see ErrDot at all in this test (because the path will be
+		// unambiguously absolute).
+		wantErrDot := false
+		t.Setenv(pathVar, "")
+		if found, err := LookPath("execabs-test"); errors.Is(err, ErrDot) {
+			wantErrDot = true
+		} else if err == nil {
+			t.Fatalf(`with PATH='', LookPath(%#q) = %#q; want non-nil error`, "execabs-test", found)
+		}
+
+		// Set PATH to include an explicit directory that contains a completely
+		// independent executable that happens to have the same name as an
+		// executable in ".". If "." is included implicitly, looking up the
+		// (unqualified) executable name will return ErrDot; otherwise, the
+		// executable in "." should have no effect and the lookup should
+		// unambiguously resolve to the directory in PATH.
+
+		dir := t.TempDir()
+		executable := "execabs-test"
+		if runtime.GOOS == "windows" {
+			executable += ".exe"
+		}
+		if err := os.WriteFile(filepath.Join(dir, executable), []byte{1, 2, 3}, 0777); err != nil {
+			t.Fatal(err)
+		}
+		t.Setenv(pathVar, dir+string(filepath.ListSeparator)+origPath)
+
+		found, err := LookPath("execabs-test")
+		if wantErrDot {
+			wantFound := filepath.Join(".", executable)
+			if found != wantFound || !errors.Is(err, ErrDot) {
+				t.Fatalf(`LookPath(%#q) = %#q, %v, want %#q, Is ErrDot`, "execabs-test", found, err, wantFound)
+			}
+		} else {
+			wantFound := filepath.Join(dir, executable)
+			if found != wantFound || err != nil {
+				t.Fatalf(`LookPath(%#q) = %#q, %v, want %#q, nil`, "execabs-test", found, err, wantFound)
+			}
+		}
+	})
+}