Improved EquivalentTo() and added Canonical()

paths.go

@@ -524,15 +524,22 @@ func (p *Path) EquivalentTo(other *Path) bool {
 	if p.Clean().path == other.Clean().path {
 		return true
 	}
-	absP, err := p.Abs()
-	if err != nil {
-		return false
+
+	if infoP, err := p.Stat(); err != nil {
+		// go ahead with the next test...
+	} else if infoOther, err := other.Stat(); err != nil {
+		// go ahead with the next test...
+	} else if os.SameFile(infoP, infoOther) {
+		return true
 	}
-	absOther, err := other.Abs()
-	if err != nil {
+
+	if absP, err := p.Abs(); err != nil {
+		return false
+	} else if absOther, err := other.Abs(); err != nil {
 		return false
+	} else {
+		return absP.path == absOther.path
 	}
-	return absP.path == absOther.path
 }
 
 // Parents returns all the parents directories of the current path. If the path is absolute
@@ -557,3 +564,18 @@ func (p *Path) Parents() []*Path {
 func (p *Path) String() string {
 	return p.path
 }
+
+// Canonical return a "canonical" Path for the given filename.
+// The meaning of "canonical" is OS-dependent but the goal of this method
+// is to always return the same path for a given file (factoring out all the
+// possibile ambiguities including, for example, relative paths traversal,
+// symlinks, drive volume letter case, etc).
+func (p *Path) Canonical() *Path {
+	canonical := p.Clone()
+	// https://github.com/golang/go/issues/17084#issuecomment-246645354
+	canonical.FollowSymLink()
+	if absPath, err := canonical.Abs(); err == nil {
+		canonical = absPath
+	}
+	return canonical
+}

paths_test.go

@@ -31,6 +31,7 @@ package paths
 
 import (
 	"path/filepath"
+	"runtime"
 	"strings"
 	"testing"
 
@@ -311,6 +312,32 @@ func TestEquivalentPaths(t *testing.T) {
 	require.True(t, New("file1", "abc").EquivalentTo(New("file1", "abc", "def", "..")))
 	require.True(t, wd.Join("file1").EquivalentTo(New("file1")))
 	require.True(t, wd.Join("file1").EquivalentTo(New("file1", "abc", "..")))
+
+	if runtime.GOOS == "windows" {
+		q := New("_testdata", "anotherFile")
+		r := New("_testdata", "ANOTHE~1")
+		require.True(t, q.EquivalentTo(r))
+		require.True(t, r.EquivalentTo(q))
+	}
+}
+
+func TestCanonicalize(t *testing.T) {
+	wd, err := Getwd()
+	require.NoError(t, err)
+
+	p := New("_testdata", "anotherFile").Canonical()
+	require.Equal(t, wd.Join("_testdata", "anotherFile").String(), p.String())
+
+	p = New("_testdata", "nonexistentFile").Canonical()
+	require.Equal(t, wd.Join("_testdata", "nonexistentFile").String(), p.String())
+
+	if runtime.GOOS == "windows" {
+		q := New("_testdata", "ANOTHE~1").Canonical()
+		require.Equal(t, wd.Join("_testdata", "anotherFile").String(), q.String())
+
+		r := New("c:\\").Canonical()
+		require.Equal(t, "C:\\", r.String())
+	}
 }
 
 func TestRelativeTo(t *testing.T) {
@@ -341,6 +368,10 @@ func TestRelativeTo(t *testing.T) {
 
 func TestWriteToTempFile(t *testing.T) {
 	tmpDir := New("_testdata", "tmp")
+	err := tmpDir.MkdirAll()
+	require.NoError(t, err)
+	defer tmpDir.RemoveAll()
+
 	tmpData := []byte("test")
 	tmp, err := WriteToTempFile(tmpData, tmpDir, "prefix")
 	defer tmp.Remove()