dot_test.go

     1  // Copyright 2022 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package exec_test
     6  
     7  import (
     8  	"errors"
     9  	"internal/testenv"
    10  	"os"
    11  	. "os/exec"
    12  	"path/filepath"
    13  	"runtime"
    14  	"strings"
    15  	"testing"
    16  )
    17  
    18  var pathVar string = func() string {
    19  	if runtime.GOOS == "plan9" {
    20  		return "path"
    21  	}
    22  	return "PATH"
    23  }()
    24  
    25  func TestLookPath(t *testing.T) {
    26  	testenv.MustHaveExec(t)
    27  	// Not parallel: uses Chdir and Setenv.
    28  
    29  	tmpDir := filepath.Join(t.TempDir(), "testdir")
    30  	if err := os.Mkdir(tmpDir, 0777); err != nil {
    31  		t.Fatal(err)
    32  	}
    33  
    34  	executable := "execabs-test"
    35  	if runtime.GOOS == "windows" {
    36  		executable += ".exe"
    37  	}
    38  	if err := os.WriteFile(filepath.Join(tmpDir, executable), []byte{1, 2, 3}, 0777); err != nil {
    39  		t.Fatal(err)
    40  	}
    41  	t.Chdir(tmpDir)
    42  	t.Logf(". is %#q", tmpDir)
    43  
    44  	origPath := os.Getenv(pathVar)
    45  
    46  	// Add "." to PATH so that exec.LookPath looks in the current directory on all systems.
    47  	// And try to trick it with "../testdir" too.
    48  	for _, errdot := range []string{"1", "0"} {
    49  		t.Run("GODEBUG=execerrdot="+errdot, func(t *testing.T) {
    50  			t.Setenv("GODEBUG", "execerrdot="+errdot+",execwait=2")
    51  			for _, dir := range []string{".", "../testdir"} {
    52  				t.Run(pathVar+"="+dir, func(t *testing.T) {
    53  					t.Setenv(pathVar, dir+string(filepath.ListSeparator)+origPath)
    54  					good := dir + "/execabs-test"
    55  					if found, err := LookPath(good); err != nil || !strings.HasPrefix(found, good) {
    56  						t.Fatalf(`LookPath(%#q) = %#q, %v, want "%s...", nil`, good, found, err, good)
    57  					}
    58  					if runtime.GOOS == "windows" {
    59  						good = dir + `\execabs-test`
    60  						if found, err := LookPath(good); err != nil || !strings.HasPrefix(found, good) {
    61  							t.Fatalf(`LookPath(%#q) = %#q, %v, want "%s...", nil`, good, found, err, good)
    62  						}
    63  					}
    64  
    65  					_, err := LookPath("execabs-test")
    66  					if errdot == "1" {
    67  						if err == nil {
    68  							t.Fatalf("LookPath didn't fail when finding a non-relative path")
    69  						} else if !errors.Is(err, ErrDot) {
    70  							t.Fatalf("LookPath returned unexpected error: want Is ErrDot, got %q", err)
    71  						}
    72  					} else {
    73  						if err != nil {
    74  							t.Fatalf("LookPath failed unexpectedly: %v", err)
    75  						}
    76  					}
    77  
    78  					cmd := Command("execabs-test")
    79  					if errdot == "1" {
    80  						if cmd.Err == nil {
    81  							t.Fatalf("Command didn't fail when finding a non-relative path")
    82  						} else if !errors.Is(cmd.Err, ErrDot) {
    83  							t.Fatalf("Command returned unexpected error: want Is ErrDot, got %q", cmd.Err)
    84  						}
    85  						cmd.Err = nil
    86  					} else {
    87  						if cmd.Err != nil {
    88  							t.Fatalf("Command failed unexpectedly: %v", err)
    89  						}
    90  					}
    91  
    92  					// Clearing cmd.Err should let the execution proceed,
    93  					// and it should fail because it's not a valid binary.
    94  					if err := cmd.Run(); err == nil {
    95  						t.Fatalf("Run did not fail: expected exec error")
    96  					} else if errors.Is(err, ErrDot) {
    97  						t.Fatalf("Run returned unexpected error ErrDot: want error like ENOEXEC: %q", err)
    98  					}
    99  				})
   100  			}
   101  		})
   102  	}
   103  
   104  	// Test the behavior when the first entry in PATH is an absolute name for the
   105  	// current directory.
   106  	//
   107  	// On Windows, "." may or may not be implicitly included before the explicit
   108  	// %PATH%, depending on the process environment;
   109  	// see https://go.dev/issue/4394.
   110  	//
   111  	// If the relative entry from "." resolves to the same executable as what
   112  	// would be resolved from an absolute entry in %PATH% alone, LookPath should
   113  	// return the absolute version of the path instead of ErrDot.
   114  	// (See https://go.dev/issue/53536.)
   115  	//
   116  	// If PATH does not implicitly include "." (such as on Unix platforms, or on
   117  	// Windows configured with NoDefaultCurrentDirectoryInExePath), then this
   118  	// lookup should succeed regardless of the behavior for ".", so it may be
   119  	// useful to run as a control case even on those platforms.
   120  	t.Run(pathVar+"=$PWD", func(t *testing.T) {
   121  		t.Setenv(pathVar, tmpDir+string(filepath.ListSeparator)+origPath)
   122  		good := filepath.Join(tmpDir, "execabs-test")
   123  		if found, err := LookPath(good); err != nil || !strings.HasPrefix(found, good) {
   124  			t.Fatalf(`LookPath(%#q) = %#q, %v, want \"%s...\", nil`, good, found, err, good)
   125  		}
   126  
   127  		if found, err := LookPath("execabs-test"); err != nil || !strings.HasPrefix(found, good) {
   128  			t.Fatalf(`LookPath(%#q) = %#q, %v, want \"%s...\", nil`, "execabs-test", found, err, good)
   129  		}
   130  
   131  		cmd := Command("execabs-test")
   132  		if cmd.Err != nil {
   133  			t.Fatalf("Command(%#q).Err = %v; want nil", "execabs-test", cmd.Err)
   134  		}
   135  	})
   136  
   137  	t.Run(pathVar+"=$OTHER", func(t *testing.T) {
   138  		// Control case: if the lookup returns ErrDot when PATH is empty, then we
   139  		// know that PATH implicitly includes ".". If it does not, then we don't
   140  		// expect to see ErrDot at all in this test (because the path will be
   141  		// unambiguously absolute).
   142  		wantErrDot := false
   143  		t.Setenv(pathVar, "")
   144  		if found, err := LookPath("execabs-test"); errors.Is(err, ErrDot) {
   145  			wantErrDot = true
   146  		} else if err == nil {
   147  			t.Fatalf(`with PATH='', LookPath(%#q) = %#q; want non-nil error`, "execabs-test", found)
   148  		}
   149  
   150  		// Set PATH to include an explicit directory that contains a completely
   151  		// independent executable that happens to have the same name as an
   152  		// executable in ".". If "." is included implicitly, looking up the
   153  		// (unqualified) executable name will return ErrDot; otherwise, the
   154  		// executable in "." should have no effect and the lookup should
   155  		// unambiguously resolve to the directory in PATH.
   156  
   157  		dir := t.TempDir()
   158  		executable := "execabs-test"
   159  		if runtime.GOOS == "windows" {
   160  			executable += ".exe"
   161  		}
   162  		if err := os.WriteFile(filepath.Join(dir, executable), []byte{1, 2, 3}, 0777); err != nil {
   163  			t.Fatal(err)
   164  		}
   165  		t.Setenv(pathVar, dir+string(filepath.ListSeparator)+origPath)
   166  
   167  		found, err := LookPath("execabs-test")
   168  		if wantErrDot {
   169  			wantFound := filepath.Join(".", executable)
   170  			if found != wantFound || !errors.Is(err, ErrDot) {
   171  				t.Fatalf(`LookPath(%#q) = %#q, %v, want %#q, Is ErrDot`, "execabs-test", found, err, wantFound)
   172  			}
   173  		} else {
   174  			wantFound := filepath.Join(dir, executable)
   175  			if found != wantFound || err != nil {
   176  				t.Fatalf(`LookPath(%#q) = %#q, %v, want %#q, nil`, "execabs-test", found, err, wantFound)
   177  			}
   178  		}
   179  	})
   180  }
   181
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