Include available choices in unknown scope diagnostics

config_test.go

@@ -255,3 +255,32 @@ func TestRequiredConfigSelectorOnlyAppliesToSelectedScopes(t *testing.T) {
 		}
 	}
 }
+
+func TestUnknownConfigScopeReportsChoicesWithoutRuntimeWork(t *testing.T) {
+	for _, tc := range []struct {
+		names   []string
+		scope   []string
+		choices string
+	}{
+		{[]string{"promptkit"}, nil, "available: promptkit"},
+		{[]string{"zeta", "alpha", "promptkit", "app"}, []string{"--scope", "unknown"}, "available: app, promptkit, alpha, zeta"},
+	} {
+		runtimeCalls := 0
+		suite := ConfigSuite[struct{}]{NewContext: func() struct{} { runtimeCalls++; return struct{}{} }}
+		for _, name := range tc.names {
+			suite.Scopes = append(suite.Scopes, ConfigScope[struct{}]{Name: name, Operations: []ConfigOperation{ConfigValidate}, Acquire: func(context.Context, ConfigRequest, struct{}) (Acquired[ConfigView], error) {
+				runtimeCalls++
+				return Acquired[ConfigView]{}, nil
+			}})
+		}
+		app, _ := New(Identity{Name: "example"})
+		if err := RegisterConfig(app, suite); err != nil {
+			t.Fatal(err)
+		}
+		var out, diagnostics bytes.Buffer
+		result := app.Execute(context.Background(), append([]string{"config", "validate"}, tc.scope...), Streams{Out: &out, Err: &diagnostics})
+		if result.Kind != OutcomeUsage || runtimeCalls != 0 || out.Len() != 0 || !strings.Contains(diagnostics.String(), tc.choices) {
+			t.Fatalf("result=%#v calls=%d out=%q diagnostics=%q", result, runtimeCalls, out.String(), diagnostics.String())
+		}
+	}
+}