Workhorse: simplify error handling in LSIF parser

Refactor the LSIF parser to use simpler error handling.

workhorse/internal/lsif_transformer/parser/errors.go

-package parser
-
-import (
-	"errors"
-	"strings"
-)
-
-func combineErrors(errsOrNil ...error) error {
-	var errs []error
-	for _, err := range errsOrNil {
-		if err != nil {
-			errs = append(errs, err)
-		}
-	}
-
-	if len(errs) == 0 {
-		return nil
-	}
-
-	if len(errs) == 1 {
-		return errs[0]
-	}
-
-	var msgs []string
-	for _, err := range errs {
-		msgs = append(msgs, err.Error())
-	}
-
-	return errors.New(strings.Join(msgs, "\n"))
-}

workhorse/internal/lsif_transformer/parser/errors_test.go

-package parser
-
-import (
-	"errors"
-	"testing"
-
-	"github.com/stretchr/testify/require"
-)
-
-type customErr struct {
-	err string
-}
-
-func (e customErr) Error() string {
-	return e.err
-}
-
-func TestCombineErrors(t *testing.T) {
-	err := combineErrors(nil, errors.New("first"), nil, customErr{"second"})
-	require.EqualError(t, err, "first\nsecond")
-
-	err = customErr{"custom error"}
-	require.Equal(t, err, combineErrors(nil, err, nil))
-
-	require.Nil(t, combineErrors(nil, nil, nil))
-}

workhorse/internal/lsif_transformer/parser/hovers.go

@@ -95,10 +95,15 @@ func (h *Hovers) For(refId Id) json.RawMessage {
 }
 
 func (h *Hovers) Close() error {
-	return combineErrors(
+	for _, err := range []error{
 		h.File.Close(),
 		h.Offsets.Close(),
-	)
+	} {
+		if err != nil {
+			return err
+		}
+	}
+	return nil
 }
 
 func (h *Hovers) addData(line []byte) error {

workhorse/internal/lsif_transformer/parser/ranges.go

@@ -130,11 +130,16 @@ func (r *Ranges) Serialize(f io.Writer, rangeIds []Id, docs map[Id]string) error
 }
 
 func (r *Ranges) Close() error {
-	return combineErrors(
+	for _, err := range []error{
 		r.Cache.Close(),
 		r.References.Close(),
 		r.Hovers.Close(),
-	)
+	} {
+		if err != nil {
+			return err
+		}
+	}
+	return nil
 }
 
 func (r *Ranges) definitionPathFor(docs map[Id]string, refId Id) string {

workhorse/internal/lsif_transformer/parser/references.go

@@ -86,10 +86,15 @@ func (r *References) For(docs map[Id]string, refId Id) []SerializedReference {
 }
 
 func (r *References) Close() error {
-	return combineErrors(
+	for _, err := range []error{
 		r.Items.Close(),
 		r.Offsets.Close(),
-	)
+	} {
+		if err != nil {
+			return err
+		}
+	}
+	return nil
 }
 
 func (r *References) getItems(refId Id) []Item {