cue: remove most uses of xerrors

Move them to the errors package to make it easier
to remove later.

Change-Id: Ib14b9daab7ee3cafe3d3cefec578ab5d351997e1
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/7681
Reviewed-by: CUE cueckoo <cueckoo@gmail.com>
Reviewed-by: Marcel van Lohuizen <mpvl@golang.org>

cue/ast/ident_test.go

@@ -19,9 +19,9 @@ import (
 	"testing"
 
 	"github.com/stretchr/testify/assert"
-	"golang.org/x/xerrors"
 
 	"cuelang.org/go/cue/ast"
+	"cuelang.org/go/cue/errors"
 	"cuelang.org/go/cue/format"
 	"cuelang.org/go/cue/token"
 )
@@ -138,7 +138,7 @@ func TestLabelName(t *testing.T) {
 			assert.Equal(t, tc.out, str, "value")
 			assert.Equal(t, tc.isIdent, isIdent, "isIdent")
 			assert.Equal(t, tc.err, err != nil, "err")
-			assert.Equal(t, tc.expr, xerrors.Is(err, ast.ErrIsExpression), "expr")
+			assert.Equal(t, tc.expr, errors.Is(err, ast.ErrIsExpression), "expr")
 		})
 	}
 }

cue/errors/errors.go

@@ -40,6 +40,33 @@ func New(msg string) error {
 	return errors.New(msg)
 }
 
+// Unwrap returns the result of calling the Unwrap method on err, if err
+// implements Unwrap. Otherwise, Unwrap returns nil.
+func Unwrap(err error) error {
+	return xerrors.Unwrap(err)
+}
+
+// Is reports whether any error in err's chain matches target.
+//
+// An error is considered to match a target if it is equal to that target or if
+// it implements a method Is(error) bool such that Is(target) returns true.
+func Is(err, target error) bool {
+	return xerrors.Is(err, target)
+}
+
+// As finds the first error in err's chain that matches the type to which target
+// points, and if so, sets the target to its value and returns true. An error
+// matches a type if it is assignable to the target type, or if it has a method
+// As(interface{}) bool such that As(target) returns true. As will panic if
+// target is not a non-nil pointer to a type which implements error or is of
+// interface type.
+//
+// The As method should set the target to its value and return true if err
+// matches the type to which target points.
+func As(err error, target interface{}) bool {
+	return xerrors.As(err, target)
+}
+
 // A Message implements the error interface as well as Message to allow
 // internationalized messages. A Message is typically used as an embedding
 // in a CUE message.

cue/load/import_test.go

@@ -19,9 +19,8 @@ import (
 	"reflect"
 	"testing"
 
-	"golang.org/x/xerrors"
-
 	"cuelang.org/go/cue/build"
+	"cuelang.org/go/cue/errors"
 	"cuelang.org/go/cue/token"
 )
 
@@ -58,7 +57,7 @@ func TestEmptyFolderImport(t *testing.T) {
 func TestIgnoredCUEFilesImport(t *testing.T) {
 	_, err := getInst(".", testdata+"ignored")
 	var e *NoFilesError
-	ok := xerrors.As(err, &e)
+	ok := errors.As(err, &e)
 	if !ok {
 		t.Fatal(`Import("testdata/ignored") did not return NoFilesError.`)
 	}

cue/load/loader.go

@@ -25,8 +25,6 @@ import (
 	"strings"
 	"unicode"
 
-	"golang.org/x/xerrors"
-
 	"cuelang.org/go/cue/ast"
 	"cuelang.org/go/cue/build"
 	"cuelang.org/go/cue/errors"
@@ -193,7 +191,7 @@ func (l *loader) cueFilesPackage(files []*build.File) *build.Instance {
 	rewriteFiles(pkg, pkg.Dir, true)
 	for _, err := range errors.Errors(fp.finalize()) { // ImportDir(&ctxt, dir, 0)
 		var x *NoFilesError
-		if len(pkg.OrphanedFiles) == 0 || !xerrors.As(err, &x) {
+		if len(pkg.OrphanedFiles) == 0 || !errors.As(err, &x) {
 			pkg.ReportError(err)
 		}
 	}

encoding/openapi/build.go

@@ -28,7 +28,6 @@ import (
 	"cuelang.org/go/cue/errors"
 	"cuelang.org/go/cue/token"
 	"cuelang.org/go/internal"
-	"golang.org/x/xerrors"
 )
 
 type buildContext struct {
@@ -564,7 +563,7 @@ func (b *builder) disjunction(a []cue.Value, f typeFunc) {
 				continue
 			}
 			err := v.Subsume(w, cue.Schema())
-			if err == nil || xerrors.Is(err, internal.ErrInexact) {
+			if err == nil || errors.Is(err, internal.ErrInexact) {
 				subsumed = append(subsumed, schemas[j])
 			}
 		}

internal/core/compile/compile.go

@@ -24,7 +24,6 @@ import (
 	"cuelang.org/go/cue/token"
 	"cuelang.org/go/internal"
 	"cuelang.org/go/internal/core/adt"
-	"golang.org/x/xerrors"
 )
 
 // Config configures a compilation.
@@ -445,7 +444,7 @@ func (c *compiler) resolve(n *ast.Ident) adt.Expr {
 		}
 		name, _, err := ast.LabelName(lab)
 		switch {
-		case xerrors.Is(err, ast.ErrIsExpression):
+		case errors.Is(err, ast.ErrIsExpression):
 			if aliasInfo.expr == nil {
 				panic("unreachable")
 			}

internal/core/debug/debug.go

@@ -30,7 +30,6 @@ import (
 	"cuelang.org/go/cue/literal"
 	"cuelang.org/go/internal"
 	"cuelang.org/go/internal/core/adt"
-	"golang.org/x/xerrors"
 )
 
 const (
@@ -102,7 +101,7 @@ func (w *printer) shortError(errs errors.Error) {
 		msg, args := errs.Msg()
 		fmt.Fprintf(w, msg, args...)
 
-		err := xerrors.Unwrap(errs)
+		err := errors.Unwrap(errs)
 		if err == nil {
 			break
 		}

internal/internal.go

@@ -27,7 +27,6 @@ import (
 	"strings"
 
 	"github.com/cockroachdb/apd/v2"
-	"golang.org/x/xerrors"
 
 	"cuelang.org/go/cue/ast"
 	"cuelang.org/go/cue/ast/astutil"
@@ -429,7 +428,7 @@ type decorated struct {
 }
 
 func (e *decorated) Is(err error) bool {
-	return xerrors.Is(e.info, err) || xerrors.Is(e.cueError, err)
+	return errors.Is(e.info, err) || errors.Is(e.cueError, err)
 }
 
 // MaxDepth indicates the maximum evaluation depth. This is there to break

pkg/tool/exec/exec.go

@@ -22,8 +22,6 @@ import (
 	"os/exec"
 	"strings"
 
-	"golang.org/x/xerrors"
-
 	"cuelang.org/go/cue"
 	"cuelang.org/go/cue/errors"
 	"cuelang.org/go/internal/task"
@@ -86,7 +84,7 @@ func (c *execCmd) Run(ctx *task.Context) (res interface{}, err error) {
 	}
 	update["success"] = err == nil
 	if err != nil {
-		if exit := (*exec.ExitError)(nil); xerrors.As(err, &exit) && captureErr {
+		if exit := (*exec.ExitError)(nil); errors.As(err, &exit) && captureErr {
 			update["stderr"] = string(exit.Stderr)
 		} else {
 			update = nil