Allow relative PATH entries on Go 1.19+

.github/workflows/go.yml

@@ -9,7 +9,7 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest, windows-latest]
-        go: [1.13, 1.14, 1.15]
+        go: [1.13, 1.14, 1.15, 1.16, 1.17, 1.18, 1.19, 1.20]
 
     runs-on: ${{matrix.os}}
     steps:

lookpath.go

@@ -1,9 +1,17 @@
-// +build !windows
+//go:build !windows && go1.19
+// +build !windows,go1.19
 
 package safeexec
 
-import "os/exec"
+import (
+	"errors"
+	"os/exec"
+)
 
 func LookPath(file string) (string, error) {
-	return exec.LookPath(file)
+	path, err := exec.LookPath(file)
+	if errors.Is(err, exec.ErrDot) {
+		return path, nil
+	}
+	return path, err
 }

lookpath_1.18.go

@@ -0,0 +1,10 @@
+//go:build !windows && !go1.19
+// +build !windows,!go1.19
+
+package safeexec
+
+import "os/exec"
+
+func LookPath(file string) (string, error) {
+	return exec.LookPath(file)
+}

lookpath_test.go

@@ -16,97 +16,117 @@ func TestLookPath(t *testing.T) {
 		t.Fatal(wderr)
 	}
 
-	paths := []string{
-		filepath.Join(root, "_fixtures", "nonexist"),
-		filepath.Join(root, "_fixtures", "system"),
-	}
-	os.Setenv("PATH", strings.Join(paths, string(filepath.ListSeparator)))
-
 	if err := os.Chdir(filepath.Join(root, "_fixtures", "cwd")); err != nil {
 		t.Fatal(err)
 	}
 
 	testCases := []struct {
 		desc    string
+		path    []string
 		pathext string
 		arg     string
 		wants   string
 		wantErr bool
 	}{
 		{
-			desc:    "no extension",
+			desc: "no extension",
+			path: []string{
+				filepath.Join(root, "_fixtures", "nonexist"),
+				filepath.Join(root, "_fixtures", "system"),
+			},
 			pathext: "",
 			arg:     "ls",
 			wants:   filepath.Join(root, "_fixtures", "system", "ls"+winonly(".exe")),
 			wantErr: false,
 		},
 		{
 			desc:    "with extension",
+			path:    []string{filepath.Join(root, "_fixtures", "system")},
 			pathext: "",
 			arg:     "ls.exe",
 			wants:   filepath.Join(root, "_fixtures", "system", "ls.exe"),
 			wantErr: false,
 		},
 		{
 			desc:    "with path",
+			path:    []string{filepath.Join(root, "_fixtures", "system")},
 			pathext: "",
 			arg:     filepath.Join("..", "system", "ls"),
 			wants:   filepath.Join("..", "system", "ls"+winonly(".exe")),
 			wantErr: false,
 		},
 		{
 			desc:    "with path+extension",
+			path:    []string{filepath.Join(root, "_fixtures", "system")},
 			pathext: "",
 			arg:     filepath.Join("..", "system", "ls.bat"),
 			wants:   filepath.Join("..", "system", "ls.bat"),
 			wantErr: false,
 		},
 		{
 			desc:    "no extension, PATHEXT",
+			path:    []string{filepath.Join(root, "_fixtures", "system")},
 			pathext: ".com;.bat",
 			arg:     "ls",
 			wants:   filepath.Join(root, "_fixtures", "system", "ls"+winonly(".bat")),
 			wantErr: false,
 		},
 		{
 			desc:    "with extension, PATHEXT",
+			path:    []string{filepath.Join(root, "_fixtures", "system")},
 			pathext: ".com;.bat",
 			arg:     "ls.exe",
 			wants:   filepath.Join(root, "_fixtures", "system", "ls.exe"),
 			wantErr: false,
 		},
 		{
-			desc:    "no extension, not found",
+			desc: "no extension, not found",
+			path: []string{
+				filepath.Join(root, "_fixtures", "nonexist"),
+				filepath.Join(root, "_fixtures", "system"),
+			},
 			pathext: "",
 			arg:     "cat",
 			wants:   "",
 			wantErr: true,
 		},
 		{
 			desc:    "with extension, not found",
+			path:    []string{filepath.Join(root, "_fixtures", "system")},
 			pathext: "",
 			arg:     "cat.exe",
 			wants:   "",
 			wantErr: true,
 		},
 		{
 			desc:    "no extension, PATHEXT, not found",
+			path:    []string{filepath.Join(root, "_fixtures", "system")},
 			pathext: ".com;.bat",
 			arg:     "cat",
 			wants:   "",
 			wantErr: true,
 		},
 		{
 			desc:    "with extension, PATHEXT, not found",
+			path:    []string{filepath.Join(root, "_fixtures", "system")},
 			pathext: ".com;.bat",
 			arg:     "cat.exe",
 			wants:   "",
 			wantErr: true,
 		},
+		{
+			desc:    "relative path",
+			path:    []string{filepath.Join("..", "system")},
+			pathext: "",
+			arg:     "ls",
+			wants:   filepath.Join("..", "system", "ls"+winonly(".exe")),
+			wantErr: false,
+		},
 	}
 	for _, tC := range testCases {
 		t.Run(tC.desc, func(t *testing.T) {
-			os.Setenv("PATHEXT", tC.pathext)
+			setenv(t, "PATH", strings.Join(tC.path, string(filepath.ListSeparator)))
+			setenv(t, "PATHEXT", tC.pathext)
 			got, err := LookPath(tC.arg)
 
 			if tC.wantErr != (err != nil) {
@@ -122,6 +142,20 @@ func TestLookPath(t *testing.T) {
 	}
 }
 
+func setenv(t *testing.T, name, newValue string) {
+	oldValue, hasOldValue := os.LookupEnv(name)
+	if err := os.Setenv(name, newValue); err != nil {
+		t.Errorf("error setting environment variable %s: %v", name, err)
+	}
+	t.Cleanup(func() {
+		if hasOldValue {
+			_ = os.Setenv(name, oldValue)
+		} else {
+			_ = os.Unsetenv(name)
+		}
+	})
+}
+
 func winonly(s string) string {
 	if runtime.GOOS == "windows" {
 		return s