internal/mod/modregistry: remove error return from New

There's no way that `modregistry.New` can fail, so remove the error,
simplifying the calls.

Signed-off-by: Roger Peppe <rogpeppe@gmail.com>
Change-Id: Ib305056b94bef2067006dd6d6bf74e296caaac4b
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1170881
TryBot-Result: CUEcueckoo <cueckoo@cuelang.org>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
Unity-Result: CUE porcuepine <cue.porcuepine@gmail.com>

cue/load/registry.go

@@ -29,12 +29,8 @@ type registryClient struct {
 // in the registry is immutable, so if it's in the cache, a module
 // will not be downloaded again.
 func newRegistryClient(registry ociregistry.Interface, cacheDir string) (*registryClient, error) {
-	client, err := modregistry.NewClient(registry)
-	if err != nil {
-		return nil, err
-	}
 	return &registryClient{
-		client:   client,
+		client:   modregistry.NewClient(registry),
 		cacheDir: cacheDir,
 	}, nil
 }

internal/mod/modregistry/client.go

@@ -51,10 +51,10 @@ const (
 
 // NewClient returns a new client that talks to the registry at the given
 // hostname.
-func NewClient(registry ociregistry.Interface) (*Client, error) {
+func NewClient(registry ociregistry.Interface) *Client {
 	return &Client{
 		registry: registry,
-	}, nil
+	}
 }
 
 // GetModule returns the module instance for the given version.

internal/mod/modregistry/client_test.go

@@ -34,9 +34,7 @@ import (
 )
 
 func newTestClient(t *testing.T) *Client {
-	c, err := NewClient(ocimem.New())
-	qt.Assert(t, qt.IsNil(err))
-	return c
+	return NewClient(ocimem.New())
 }
 
 func TestPutGetModule(t *testing.T) {

internal/registrytest/registry.go

@@ -36,10 +36,7 @@ import (
 // The Registry should be closed after use.
 func New(fsys fs.FS, prefix string) (*Registry, error) {
 	r := ocimem.New()
-	client, err := modregistry.NewClient(ocifilter.Sub(r, prefix))
-	if err != nil {
-		return nil, fmt.Errorf("cannot make client: %v", err)
-	}
+	client := modregistry.NewClient(ocifilter.Sub(r, prefix))
 
 	mods, err := getModules(fsys)
 	if err != nil {

internal/registrytest/registry_test.go

@@ -50,10 +50,7 @@ func TestRegistry(t *testing.T) {
 
 func runTest(t *testing.T, registry ociregistry.Interface, script string, ar *txtar.Archive) {
 	ctx := context.Background()
-	client, err := modregistry.NewClient(registry)
-	if err != nil {
-		t.Fatal(err)
-	}
+	client := modregistry.NewClient(registry)
 	for _, line := range strings.Split(script, "\n") {
 		if line == "" || line[0] == '#' {
 			continue