thema: One Translate(), with error return

cmd/thema/data.go

@@ -10,9 +10,10 @@ import (
 	"path/filepath"
 
 	"cuelang.org/go/cue"
+	"github.com/spf13/cobra"
+
 	"github.com/grafana/thema"
 	"github.com/grafana/thema/vmux"
-	"github.com/spf13/cobra"
 )
 
 type dataCommand struct {
@@ -180,8 +181,11 @@ func (dc *dataCommand) runTranslate(cmd *cobra.Command, args []string) error {
 	}
 
 	// Prior validations checked that the schema version exists in the lineage
-	tinst, lac := inst.Translate(dc.lla.dl.sch.Version())
-	if err := dc.validateTranslationResult(tinst, lac); err != nil {
+	tinst, lac, err := inst.Translate(dc.lla.dl.sch.Version())
+	if err != nil {
+		return err
+	}
+	if err = dc.validateTranslationResult(tinst, lac); err != nil {
 		return err
 	}
 

errors/errors.go

@@ -67,7 +67,7 @@ var (
 )
 
 // Translation errors. These all occur as a result of an invalid lens. Currently
-// these may be returned from [thema.Instance.TranslateErr]. Eventually, it is
+// these may be returned from [thema.Instance.Translate]. Eventually, it is
 // hoped that they will be caught statically in [thema.BindLineage] and cannot
 // occur at runtime.
 var (

instance.go

@@ -7,6 +7,7 @@ import (
 	cerrors "cuelang.org/go/cue/errors"
 	"cuelang.org/go/pkg/encoding/json"
 	"github.com/cockroachdb/errors"
+
 	terrors "github.com/grafana/thema/errors"
 )
 
@@ -97,14 +98,14 @@ func (i *Instance) Dehydrate() *Instance {
 
 // AsSuccessor translates the instance into the form specified by the successor
 // schema.
-func (i *Instance) AsSuccessor() (*Instance, TranslationLacunas) {
+func (i *Instance) AsSuccessor() (*Instance, TranslationLacunas, error) {
 	i.check()
 	return i.Translate(i.sch.Successor().Version())
 }
 
 // AsPredecessor translates the instance into the form specified by the predecessor
 // schema.
-func (i *Instance) AsPredecessor() (*Instance, TranslationLacunas) {
+func (i *Instance) AsPredecessor() (*Instance, TranslationLacunas, error) {
 	i.check()
 	return i.Translate(i.sch.Predecessor().Version())
 }
@@ -170,22 +171,7 @@ func (inst *TypedInstance[T]) ValueP() T {
 	return t
 }
 
-// Translate is [Instance.TranslateErr], but panics if an error is encountered.
-//
-// Errors can only occur in Translate if lenses are not written correctly.
-// Eventually, it is hoped that all possible error cases on lenses will be
-// determinable statically, and turned into lineage validity errors that are
-// caught by [BindLineage]. If that goal is reached, this function will never
-// panic, and [Instance.TranslateErr] will be deprecated.
-func (i *Instance) Translate(to SyntacticVersion) (*Instance, TranslationLacunas) {
-	inst, lac, err := i.TranslateErr(to)
-	if err != nil {
-		panic(err)
-	}
-	return inst, lac
-}
-
-// TranslateErr transforms the provided [Instance] to an Instance of a different
+// Translate transforms the provided [Instance] to an Instance of a different
 // [Schema] from the same [Lineage]. A new *Instance is returned representing the
 // transformed value, along with any lacunas accumulated along the way.
 //
@@ -209,7 +195,7 @@ func (i *Instance) Translate(to SyntacticVersion) (*Instance, TranslationLacunas
 // Errors only occur in cases where lenses were written in an unexpected way -
 // for example, not all fields were mapped over, and the resulting object is not
 // concrete. All errors returned from this func will children of [terrors.ErrInvalidLens].
-func (i *Instance) TranslateErr(to SyntacticVersion) (*Instance, TranslationLacunas, error) {
+func (i *Instance) Translate(to SyntacticVersion) (*Instance, TranslationLacunas, error) {
 	i.check()
 
 	// TODO define this in terms of AsSuccessor and AsPredecessor, rather than those in terms of this.

instance_test.go

@@ -35,7 +35,8 @@ func TestInstance_Translate(t *testing.T) {
 		for from := lin.First(); from != nil; from = from.Successor() {
 			for _, example := range from.Examples() {
 				for to := lin.First(); to != nil; to = to.Successor() {
-					tinst, lacunas := example.Translate(to.Version())
+					tinst, lacunas, err := example.Translate(to.Version())
+					require.NoError(t, err)
 					require.NotNil(t, tinst)
 
 					result := tinst.Underlying()
@@ -127,7 +128,8 @@ schemas: [
 	require.Equal(t, expected, got)
 
 	// Translate cue.Value (no lacunas)
-	tinst, _ := inst.Translate(SV(0, 1))
+	tinst, _, err := inst.Translate(SV(0, 1))
+	require.NoError(t, err)
 	require.Equal(t, SV(0, 0), inst.Schema().Version())
 
 	got, err = tinst.Underlying().LookupPath(cue.ParsePath("title")).String()

vmux/typed.go

@@ -48,7 +48,11 @@ func NewTypedMux[T thema.Assignee](sch thema.TypedSchema[T], dec Decoder) TypedM
 			}
 
 			if inst, ierr := isch.Validate(v); ierr == nil {
-				trinst, lac := inst.Translate(sch.Version())
+				trinst, lac, err := inst.Translate(sch.Version())
+				if err != nil {
+
+				}
+				// TODO perf: introduce a typed translator to avoid wastefully re-binding the go type every time
 				tinst, err := thema.BindInstanceType(trinst, sch)
 				if err != nil {
 					panic(fmt.Errorf("unreachable, instance type should always be bindable: %w", err))

vmux/untyped.go

@@ -48,8 +48,7 @@ func NewUntypedMux(sch thema.Schema, dec Decoder) UntypedMux {
 			}
 
 			if inst, ierr := isch.Validate(v); ierr == nil {
-				trinst, lac := inst.Translate(sch.Version())
-				return trinst, lac, nil
+				return inst.Translate(sch.Version())
 			}
 		}