fix(ui): hide platform-mapping filters that have no options (#247)

Category and Family are populated from IGDB platform metadata that RomM
often leaves empty, so their filter rows showed only "All" and did nothing.
Build each metadata filter's values via distinctPlatformValues and only show
the row when it has at least one value (Generation gated the same way).

Author: BrandonKowalski

ui/settings_platform_mapping.go

@@ -43,6 +43,24 @@ func NewPlatformMappingScreen() *PlatformMappingScreen {
 	return &PlatformMappingScreen{}
 }
 
+// distinctPlatformValues returns the sorted, deduplicated, non-empty values produced
+// by get across platforms. An empty result means the corresponding metadata filter has
+// no options and should be hidden rather than shown as an "All"-only picker.
+func distinctPlatformValues(platforms []romm.Platform, get func(romm.Platform) string) []string {
+	set := make(map[string]bool)
+	for _, p := range platforms {
+		if v := get(p); v != "" {
+			set[v] = true
+		}
+	}
+	values := make([]string, 0, len(set))
+	for v := range set {
+		values = append(values, v)
+	}
+	slices.Sort(values)
+	return values
+}
+
 func (s *PlatformMappingScreen) Draw(input PlatformMappingInput) (PlatformMappingOutput, error) {
 	logger := gaba.GetLogger()
 	output := PlatformMappingOutput{Action: PlatformMappingActionBack, Mappings: make(map[string]internal.DirectoryMapping)}
@@ -223,17 +241,7 @@ func (s *PlatformMappingScreen) Draw(input PlatformMappingInput) (PlatformMappin
 				}
 
 				// Build dynamic list of categories present in rommPlatforms
-				categorySet := make(map[string]bool)
-				for _, p := range rommPlatforms {
-					if p.Category != "" {
-						categorySet[p.Category] = true
-					}
-				}
-				var uniqueCategories []string
-				for c := range categorySet {
-					uniqueCategories = append(uniqueCategories, c)
-				}
-				slices.Sort(uniqueCategories)
+				uniqueCategories := distinctPlatformValues(rommPlatforms, func(p romm.Platform) string { return p.Category })
 
 				categoryOptions := []gaba.Option{
 					{DisplayName: i18n.Localize(&goi18n.Message{ID: "filter_all", Other: "All"}, nil), Value: "all"},
@@ -250,17 +258,7 @@ func (s *PlatformMappingScreen) Draw(input PlatformMappingInput) (PlatformMappin
 				}
 
 				// Build dynamic list of families present in rommPlatforms
-				familySet := make(map[string]bool)
-				for _, p := range rommPlatforms {
-					if p.Family != "" {
-						familySet[p.Family] = true
-					}
-				}
-				var uniqueFamilies []string
-				for f := range familySet {
-					uniqueFamilies = append(uniqueFamilies, f)
-				}
-				slices.Sort(uniqueFamilies)
+				uniqueFamilies := distinctPlatformValues(rommPlatforms, func(p romm.Platform) string { return p.Family })
 
 				familyOptions := []gaba.Option{
 					{DisplayName: i18n.Localize(&goi18n.Message{ID: "filter_all", Other: "All"}, nil), Value: "all"},
@@ -298,27 +296,38 @@ func (s *PlatformMappingScreen) Draw(input PlatformMappingInput) (PlatformMappin
 						},
 						SelectedOption: boolToIndex(showGamesOnlySub),
 					},
-					{
+				}
+
+				// Only show a metadata filter when RomM actually populated values for it —
+				// otherwise it's a useless "All"-only picker (#247). Category/Family are
+				// frequently empty (they require IGDB platform metadata); Generation usually
+				// has values but is gated the same way for consistency.
+				if len(uniqueCategories) > 0 {
+					filterItems = append(filterItems, gaba.ItemWithOptions{
 						Item: gaba.MenuItem{
 							Text: i18n.Localize(&goi18n.Message{ID: "settings_category", Other: "Category"}, nil),
 						},
 						Options:        categoryOptions,
 						SelectedOption: categorySelectedIndex,
-					},
-					{
+					})
+				}
+				if len(uniqueFamilies) > 0 {
+					filterItems = append(filterItems, gaba.ItemWithOptions{
 						Item: gaba.MenuItem{
 							Text: i18n.Localize(&goi18n.Message{ID: "settings_family", Other: "Family"}, nil),
 						},
 						Options:        familyOptions,
 						SelectedOption: familySelectedIndex,
-					},
-					{
+					})
+				}
+				if len(uniqueGenerations) > 0 {
+					filterItems = append(filterItems, gaba.ItemWithOptions{
 						Item: gaba.MenuItem{
 							Text: i18n.Localize(&goi18n.Message{ID: "settings_generation", Other: "Generation"}, nil),
 						},
 						Options:        generationOptions,
 						SelectedOption: generationSelectedIndex,
-					},
+					})
 				}
 
 				filterResult, err := gaba.OptionsList(

ui/settings_platform_mapping_test.go

@@ -0,0 +1,46 @@
+package ui
+
+import (
+	"slices"
+	"testing"
+
+	"grout/romm"
+)
+
+// The platform-mapping filters (Category/Family) are built from the distinct values
+// present across platforms; when RomM doesn't populate a field, the list is empty and
+// the filter row must be hidden instead of showing a useless "All"-only picker (#247).
+func TestDistinctPlatformValues(t *testing.T) {
+	platforms := []romm.Platform{
+		{Category: "console", Family: "Nintendo"},
+		{Category: "handheld", Family: "Nintendo"},
+		{Category: "console", Family: "Sega"}, // duplicate category
+		{Category: "", Family: ""},            // empty values are skipped
+	}
+
+	gotCategory := distinctPlatformValues(platforms, func(p romm.Platform) string { return p.Category })
+	if want := []string{"console", "handheld"}; !slices.Equal(gotCategory, want) {
+		t.Errorf("category values = %v, want %v (sorted, deduped, no empties)", gotCategory, want)
+	}
+
+	gotFamily := distinctPlatformValues(platforms, func(p romm.Platform) string { return p.Family })
+	if want := []string{"Nintendo", "Sega"}; !slices.Equal(gotFamily, want) {
+		t.Errorf("family values = %v, want %v", gotFamily, want)
+	}
+}
+
+func TestDistinctPlatformValues_AllEmptyHidesFilter(t *testing.T) {
+	// RomM returned no category/family metadata for any platform: the result is empty,
+	// which is the signal to hide the filter entirely.
+	platforms := []romm.Platform{
+		{Category: "", Family: "", Generation: 3},
+		{Category: "", Family: "", Generation: 4},
+	}
+
+	if got := distinctPlatformValues(platforms, func(p romm.Platform) string { return p.Category }); len(got) != 0 {
+		t.Errorf("expected no category values (filter hidden), got %v", got)
+	}
+	if got := distinctPlatformValues(platforms, func(p romm.Platform) string { return p.Family }); len(got) != 0 {
+		t.Errorf("expected no family values (filter hidden), got %v", got)
+	}
+}