imagefilter: implement SupportedOutputFormats()

Implements function to get a list of all supported output formats.

go.mod

@@ -32,6 +32,7 @@ require (
 	github.com/stretchr/testify v1.10.0
 	github.com/ubccr/kerby v0.0.0-20230802201021-412be7bfaee5
 	github.com/vmware/govmomi v0.48.0
+	golang.org/x/exp v0.0.0-20241009180824-f66d83c29e7c
 	golang.org/x/oauth2 v0.25.0
 	golang.org/x/sys v0.29.0
 	golang.org/x/tools v0.26.0
@@ -168,7 +169,6 @@ require (
 	go.opentelemetry.io/otel/sdk/metric v1.32.0 // indirect
 	go.opentelemetry.io/otel/trace v1.32.0 // indirect
 	golang.org/x/crypto v0.32.0 // indirect
-	golang.org/x/exp v0.0.0-20241009180824-f66d83c29e7c // indirect
 	golang.org/x/mod v0.21.0 // indirect
 	golang.org/x/net v0.34.0 // indirect
 	golang.org/x/sync v0.10.0 // indirect

pkg/imagefilter/export_test.go

@@ -0,0 +1,3 @@
+package imagefilter
+
+var SupportedFormatterMap = supportedFormatters

pkg/imagefilter/formatter.go

@@ -9,6 +9,8 @@ import (
 	"strings"
 
 	"github.com/osbuild/images/pkg/distrosort"
+	// we cannot use "maps" yet, as it needs go1.23
+	"golang.org/x/exp/maps"
 )
 
 // OutputFormat contains the valid output formats for formatting results
@@ -27,20 +29,28 @@ type ResultsFormatter interface {
 	Output(io.Writer, []Result) error
 }
 
-// NewResultFormatter will create a formatter based on the given format.
+var supportedFormatters = map[string]ResultsFormatter{
+	string(OutputFormatDefault):   &textResultsFormatter{},
+	string(OutputFormatText):      &textResultsFormatter{},
+	string(OutputFormatJSON):      &jsonResultsFormatter{},
+	string(OutputFormatTextShell): &shellResultsFormatter{},
+	string(OutputFormatTextShort): &textShortResultsFormatter{},
+}
+
+// SupportedOutputFormats returns a list of supported output formats
+func SupportedOutputFormats() []string {
+	keys := maps.Keys(supportedFormatters)
+	sort.Strings(keys)
+	return keys
+}
+
+// NewResultsFormatter will create a formatter based on the given format.
 func NewResultsFormatter(format OutputFormat) (ResultsFormatter, error) {
-	switch format {
-	case OutputFormatDefault, OutputFormatText:
-		return &textResultsFormatter{}, nil
-	case OutputFormatJSON:
-		return &jsonResultsFormatter{}, nil
-	case OutputFormatTextShell:
-		return &shellResultsFormatter{}, nil
-	case OutputFormatTextShort:
-		return &textShortResultsFormatter{}, nil
-	default:
+	rs, ok := supportedFormatters[string(format)]
+	if !ok {
 		return nil, fmt.Errorf("unsupported formatter %q", format)
 	}
+	return rs, nil
 }
 
 type textResultsFormatter struct{}

pkg/imagefilter/formatter_test.go

@@ -2,6 +2,7 @@ package imagefilter_test
 
 import (
 	"bytes"
+	"sort"
 	"strings"
 	"testing"
 
@@ -105,3 +106,13 @@ func TestResultsFormatter(t *testing.T) {
 		assert.Equal(t, tc.expectsOutput, buf.String(), tc)
 	}
 }
+
+func TestSupportedOutputFormats(t *testing.T) {
+	formatters := imagefilter.SupportedOutputFormats()
+	assert.Len(t, formatters, len(imagefilter.SupportedFormatterMap))
+	assert.Contains(t, formatters, "text")
+	assert.Contains(t, formatters, "json")
+	assert.Contains(t, formatters, "shell")
+	assert.Contains(t, formatters, "short")
+	assert.True(t, sort.StringsAreSorted(formatters))
+}