Protect canonical operand prefixes from aliases

registry_test.go

@@ -203,6 +203,40 @@ func TestCommandAliasesRejectCanonicalRoutesAndOperands(t *testing.T) {
 	}
 }
 
+func TestCommandAliasesProtectIncompleteCanonicalOperandPrefixes(t *testing.T) {
+	for _, bounds := range []struct{ min, max int }{{2, 2}, {3, -1}} {
+		t.Run(fmt.Sprintf("%d_%d", bounds.min, bounds.max), func(t *testing.T) {
+			run := runnableWithOperands("run", bounds.min, bounds.max)
+			mapping := Alias("run first", "inspect")
+			if _, err := New(Identity{Name: "Example"}, run, simpleRunnable("inspect"), mapping); err == nil {
+				t.Fatal("construction accepted an alias intercepting an operand prefix")
+			}
+			for _, aliasFirst := range []bool{false, true} {
+				app, err := New(Identity{Name: "Example"}, simpleRunnable("inspect"))
+				if err != nil {
+					t.Fatal(err)
+				}
+				var first, second Declaration = run, mapping
+				if aliasFirst {
+					first, second = second, first
+				}
+				if err := app.Register(first); err != nil {
+					t.Fatal(err)
+				}
+				if err := app.Register(second, simpleRunnable("unrelated")); err == nil {
+					t.Fatal("later registration accepted an operand interception")
+				}
+				if app.commands["unrelated"] != nil || (app.commands["run"] != nil) == aliasFirst {
+					t.Fatal("rejected batch changed canonical registration")
+				}
+				if (len(app.routingRules) == 1) != aliasFirst {
+					t.Fatal("rejected batch changed alias registration")
+				}
+			}
+		})
+	}
+}
+
 func TestLongerAliasBeneathAlternateSpellingCanUseOperandWords(t *testing.T) {
 	app, err := New(Identity{Name: "Example"},
 		runnableWithOperands("run", 1, 1),