Merge pull request #459 from aduong/symlinks

Overwrite existing dest when copying symlink and preserve link target

pkg/util/fs_util.go

@@ -509,8 +509,12 @@ func CopySymlink(src, dest string) error {
 	if err != nil {
 		return err
 	}
-	linkDst := filepath.Join(dest, link)
+	if FilepathExists(dest) {
-	return os.Symlink(linkDst, dest)
+		if err := os.RemoveAll(dest); err != nil {
+			return err
+		}
+	}
+	return os.Symlink(link, dest)
 }
 
 // CopyFile copies the file at src to dest

pkg/util/fs_util_test.go

@@ -536,3 +536,63 @@ func TestExtractFile(t *testing.T) {
 		})
 	}
 }
+
+func TestCopySymlink(t *testing.T) {
+	type tc struct {
+		name       string
+		linkTarget string
+		dest       string
+		beforeLink func(r string) error
+	}
+
+	tcs := []tc{{
+		name:       "absolute symlink",
+		linkTarget: "/abs/dest",
+	}, {
+		name:       "relative symlink",
+		linkTarget: "rel",
+	}, {
+		name:       "symlink copy overwrites existing file",
+		linkTarget: "/abs/dest",
+		dest:       "overwrite_me",
+		beforeLink: func(r string) error {
+			return ioutil.WriteFile(filepath.Join(r, "overwrite_me"), nil, 0644)
+		},
+	}}
+
+	for _, tc := range tcs {
+		t.Run(tc.name, func(t *testing.T) {
+			tc := tc
+			t.Parallel()
+			r, err := ioutil.TempDir("", "")
+			if err != nil {
+				t.Fatal(err)
+			}
+			defer os.RemoveAll(r)
+
+			if tc.beforeLink != nil {
+				if err := tc.beforeLink(r); err != nil {
+					t.Fatal(err)
+				}
+			}
+			link := filepath.Join(r, "link")
+			dest := filepath.Join(r, "copy")
+			if tc.dest != "" {
+				dest = filepath.Join(r, tc.dest)
+			}
+			if err := os.Symlink(tc.linkTarget, link); err != nil {
+				t.Fatal(err)
+			}
+			if err := CopySymlink(link, dest); err != nil {
+				t.Fatal(err)
+			}
+			got, err := os.Readlink(dest)
+			if err != nil {
+				t.Fatalf("error reading link %s: %s", link, err)
+			}
+			if got != tc.linkTarget {
+				t.Errorf("link target does not match: %s != %s", got, tc.linkTarget)
+			}
+		})
+	}
+}