Memoize flag alias resolution by context

flag_aliases_test.go

@@ -295,3 +295,21 @@ func capturedSpelling(token string) capturedFlagSpelling {
 	issues := []error(nil)
 	return captureFlagSpelling("test", token, &issues)
 }
+
+func TestFlagAliasSharedSuffixAndUnavailableDestination(t *testing.T) {
+	app, err := New(Identity{Name: "Example"}, flagAliasCommand("active", stringFlag("color", "")), flagAliasCommand("inactive"),
+		FlagAlias("--first", "--common"), FlagAlias("--second", "--common"), FlagAlias("--common", "--color"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, name := range []string{"first", "second", "common"} {
+		key := flagSpellingKey(capturedFlagSpelling{name: name})
+		active := app.flagAliases[commandpath.Path{"active"}.Key()].bySpelling
+		if alias, ok := active[key]; !ok || alias.target.token() != "--color" {
+			t.Fatalf("active %s = %#v", name, alias)
+		}
+		if _, ok := app.flagAliases[commandpath.Path{"inactive"}.Key()].bySpelling[key]; ok {
+			t.Fatalf("inactive %s was installed", name)
+		}
+	}
+}