[syserror] Add conversions to linuxerr with temporary Equals method.

Add Equals method to compare syserror and unix.Errno errors to linuxerr errors.
This will facilitate removal of syserror definitions in a followup, and
finding needed conversions from unix.Errno to linuxerr.

PiperOrigin-RevId: 380909667

3 files changed, 82 insertions, 0 deletions

diff --git a/pkg/errors/linuxerr/BUILD b/pkg/errors/linuxerr/BUILD
index 8afc9688c..201727780 100644
--- a/pkg/errors/linuxerr/BUILD
+++ b/pkg/errors/linuxerr/BUILD
@@ -9,6 +9,7 @@ go_library(
     deps = [
         "//pkg/abi/linux/errno",
         "//pkg/errors",
+        "@org_golang_x_sys//unix:go_default_library",
     ],
 )
 
diff --git a/pkg/errors/linuxerr/linuxerr.go b/pkg/errors/linuxerr/linuxerr.go
index bbdcdecd0..9246f2e89 100644
--- a/pkg/errors/linuxerr/linuxerr.go
+++ b/pkg/errors/linuxerr/linuxerr.go
@@ -20,6 +20,7 @@ package linuxerr
 import (
 	"fmt"
 
+	"golang.org/x/sys/unix"
 	"gvisor.dev/gvisor/pkg/abi/linux/errno"
 	"gvisor.dev/gvisor/pkg/errors"
 )
@@ -325,3 +326,22 @@ func ErrorFromErrno(e errno.Errno) *errors.Error {
 	}
 	panic(fmt.Sprintf("invalid error requested with errno: %d", e))
 }
+
+// Equals compars a linuxerr to a given error
+// TODO(b/34162363): Remove when syserror is removed.
+func Equals(e *errors.Error, err error) bool {
+	if err == nil {
+		return e == NOERROR || e == nil
+	}
+	if e == nil {
+		return err == NOERROR || err == unix.Errno(0)
+	}
+
+	switch err.(type) {
+	case *errors.Error:
+		return e == err
+	case unix.Errno, error:
+		return unix.Errno(e.Errno()) == err
+	}
+	return false
+}
diff --git a/pkg/errors/linuxerr/linuxerr_test.go b/pkg/errors/linuxerr/linuxerr_test.go
index a81dd9560..62743c338 100644
--- a/pkg/errors/linuxerr/linuxerr_test.go
+++ b/pkg/errors/linuxerr/linuxerr_test.go
@@ -16,6 +16,8 @@ package syserror_test
 
 import (
 	"errors"
+	"io"
+	"io/fs"
 	"syscall"
 	"testing"
 
@@ -243,3 +245,62 @@ func TestSyscallErrnoToErrors(t *testing.T) {
 		})
 	}
 }
+
+// TestEqualsMethod tests that the Equals method correctly compares syerror,
+// unix.Errno and linuxerr.
+// TODO (b/34162363): Remove this.
+func TestEqualsMethod(t *testing.T) {
+	for _, tc := range []struct {
+		name     string
+		linuxErr []*gErrors.Error
+		err      []error
+		equal    bool
+	}{
+		{
+			name:     "compare nil",
+			linuxErr: []*gErrors.Error{nil, linuxerr.NOERROR},
+			err:      []error{nil, linuxerr.NOERROR, unix.Errno(0)},
+			equal:    true,
+		},
+		{
+			name:     "linuxerr nil error not",
+			linuxErr: []*gErrors.Error{nil, linuxerr.NOERROR},
+			err:      []error{unix.Errno(1), linuxerr.EPERM, syserror.EACCES},
+			equal:    false,
+		},
+		{
+			name:     "linuxerr not nil error nil",
+			linuxErr: []*gErrors.Error{linuxerr.ENOENT},
+			err:      []error{nil, unix.Errno(0), linuxerr.NOERROR},
+			equal:    false,
+		},
+		{
+			name:     "equal errors",
+			linuxErr: []*gErrors.Error{linuxerr.ESRCH},
+			err:      []error{linuxerr.ESRCH, syserror.ESRCH, unix.Errno(linuxerr.ESRCH.Errno())},
+			equal:    true,
+		},
+		{
+			name:     "unequal errors",
+			linuxErr: []*gErrors.Error{linuxerr.ENOENT},
+			err:      []error{linuxerr.ESRCH, syserror.ESRCH, unix.Errno(linuxerr.ESRCH.Errno())},
+			equal:    false,
+		},
+		{
+			name:     "other error",
+			linuxErr: []*gErrors.Error{nil, linuxerr.NOERROR, linuxerr.E2BIG, linuxerr.EINVAL},
+			err:      []error{fs.ErrInvalid, io.EOF},
+			equal:    false,
+		},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			for _, le := range tc.linuxErr {
+				for _, e := range tc.err {
+					if linuxerr.Equals(le, e) != tc.equal {
+						t.Fatalf("Expected %t from Equals method for linuxerr: %s %T and error: %s %T", tc.equal, le, le, e, e)
+					}
+				}
+			}
+		})
+	}
+}