distro: don't use a global variable to store the distro register

Introduce a DistroRegister object. For now this does not introduce
any functional changes, as the object is always instantited to be
the same. However, in follow-up patches it will get options.

Signed-off-by: Tom Gundersen <teg@jklm.no>

internal/distro/distro.go

@@ -40,17 +40,29 @@ type Distro interface {
 	Runner() string
 }
 
-var registered map[string]Distro
-
-func init() {
-	registered = map[string]Distro{
-		fedora30.Name: fedora30.New(),
-		rhel82.Name:   rhel82.New(),
-	}
+type Registry struct {
+	distros map[string]Distro
 }
 
-func New(name string) Distro {
-	distro, ok := registered[name]
+func NewRegistry() *Registry {
+	distros := &Registry{
+		distros: make(map[string]Distro),
+	}
+	distros.register(fedora30.New())
+	distros.register(rhel82.New())
+	return distros
+}
+
+func (r *Registry) register(distro Distro) {
+	name := distro.Name()
+	if _, exists := r.distros[name]; exists {
+		panic("a distro with this name already exists: " + name)
+	}
+	r.distros[name] = distro
+}
+
+func (r *Registry) GetDistro(name string) Distro {
+	distro, ok := r.distros[name]
 	if !ok {
 		return nil
 	}
@@ -58,7 +70,7 @@ func New(name string) Distro {
 	return distro
 }
 
-func FromHost() (Distro, error) {
+func (r *Registry) FromHost() (Distro, error) {
 	f, err := os.Open("/etc/os-release")
 	if err != nil {
 		return nil, err
@@ -72,7 +84,7 @@ func FromHost() (Distro, error) {
 
 	name := osrelease["ID"] + "-" + osrelease["VERSION_ID"]
 
-	d := New(name)
+	d := r.GetDistro(name)
 	if d == nil {
 		return nil, errors.New("unknown distro: " + name)
 	}
@@ -80,13 +92,6 @@ func FromHost() (Distro, error) {
 	return d, nil
 }
 
-func Register(name string, distro Distro) {
-	if _, exists := registered[name]; exists {
-		panic("a distro with this name already exists: " + name)
-	}
-	registered[name] = distro
-}
-
 func readOSRelease(r io.Reader) (map[string]string, error) {
 	osrelease := make(map[string]string)
 	scanner := bufio.NewScanner(r)

internal/distro/distro_test.go

@@ -42,7 +42,8 @@ func TestDistro_Pipeline(t *testing.T) {
 			continue
 		}
 		t.Run(tt.Compose.OutputFormat, func(t *testing.T) {
-			d := distro.New(tt.Compose.Distro)
+			distros := distro.NewRegistry()
+			d := distros.GetDistro(tt.Compose.Distro)
 			if d == nil {
 				t.Errorf("unknown distro: %v", tt.Compose.Distro)
 				return

internal/distro/fedora30/distro_test.go

@@ -19,7 +19,8 @@ func TestListOutputFormats(t *testing.T) {
 		"vmdk",
 	}
 
-	f30 := distro.New("fedora-30")
+	distros := distro.NewRegistry()
+	f30 := distros.GetDistro("fedora-30")
 	if got := f30.ListOutputFormats(); !reflect.DeepEqual(got, want) {
 		t.Errorf("ListOutputFormats() = %v, want %v", got, want)
 	}
@@ -92,7 +93,8 @@ func TestFilenameFromType(t *testing.T) {
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			f30 := distro.New("fedora-30")
+			distros := distro.NewRegistry()
+			f30 := distros.GetDistro("fedora-30")
 			got, got1, err := f30.FilenameFromType(tt.args.outputFormat)
 			if (err != nil) != tt.wantErr {
 				t.Errorf("FilenameFromType() error = %v, wantErr %v", err, tt.wantErr)

internal/distro/rhel82/distro_test.go

@@ -19,8 +19,9 @@ func TestListOutputFormats(t *testing.T) {
 		"vmdk",
 	}
 
-	f31 := distro.New("rhel-8.2")
-	if got := f31.ListOutputFormats(); !reflect.DeepEqual(got, want) {
+	distros := distro.NewRegistry()
+	rhel82 := distros.GetDistro("rhel-8.2")
+	if got := rhel82.ListOutputFormats(); !reflect.DeepEqual(got, want) {
 		t.Errorf("ListOutputFormats() = %v, want %v", got, want)
 	}
 }
@@ -92,8 +93,9 @@ func TestFilenameFromType(t *testing.T) {
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			f31 := distro.New("rhel-8.2")
-			got, got1, err := f31.FilenameFromType(tt.args.outputFormat)
+			distros := distro.NewRegistry()
+			rhel82 := distros.GetDistro("rhel-8.2")
+			got, got1, err := rhel82.FilenameFromType(tt.args.outputFormat)
 			if (err != nil) != tt.wantErr {
 				t.Errorf("FilenameFromType() error = %v, wantErr %v", err, tt.wantErr)
 				return

internal/distro/test/distro.go

@@ -4,7 +4,6 @@ import (
 	"errors"
 
 	"github.com/osbuild/osbuild-composer/internal/blueprint"
-	"github.com/osbuild/osbuild-composer/internal/distro"
 	"github.com/osbuild/osbuild-composer/internal/pipeline"
 	"github.com/osbuild/osbuild-composer/internal/rpmmd"
 )
@@ -13,8 +12,8 @@ type TestDistro struct{}
 
 const Name = "test"
 
-func init() {
-	distro.Register(Name, &TestDistro{})
+func New() *TestDistro {
+	return &TestDistro{}
 }
 
 func (d *TestDistro) Name() string {