Test internal/grammar, and allow the root to import it

internal/grammar/format_test.go

@@ -0,0 +1,47 @@
+package grammar
+
+import (
+	"reflect"
+	"testing"
+)
+
+// TestSplitArgsQuotesOutsideSelectors pins the arg grammar: a comma splits outside a
+// selector and outside a quoted layout, and a quote inside a selector is a name's text.
+func TestSplitArgsQuotesOutsideSelectors(t *testing.T) {
+	for in, want := range map[string][]string{
+		"a, b": {"a", "b"},
+		"1990-01-01,1990-12-31,'January 2, 2006'": {"1990-01-01", "1990-12-31", "'January 2, 2006'"},
+		"/geo.US.locality[O'Fallon].name, 2":      {"/geo.US.locality[O'Fallon].name", "2"},
+		"'[a,b]'":                                 {"'[a,b]'"},
+	} {
+		if got := SplitArgs(in); !reflect.DeepEqual(got, want) {
+			t.Errorf("SplitArgs(%q) = %q, want %q", in, got, want)
+		}
+	}
+}
+
+func TestParseFormatReadsEachTokenKind(t *testing.T) {
+	toks, err := ParseFormat("a{{{x|/y.z[a.b]}{/p as q}{f(1, n)}", func(fn string, args []string) []string {
+		return args[1:]
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	want := []Token{
+		{Kind: LiteralRun, Lit: "a{"},
+		{Kind: NameRead, Body: "x|/y.z[a.b]", Names: []string{"x", "/y.z[a.b]"}},
+		{Kind: NameBind, Body: "/p as q", BoundRef: "/p", Bound: "q"},
+		{Kind: BuiltinCall, Body: "f(1, n)", Fn: "f", Args: []string{"1", "n"}, Names: []string{"n"}},
+	}
+	if !reflect.DeepEqual(toks, want) {
+		t.Errorf("ParseFormat = %+v, want %+v", toks, want)
+	}
+}
+
+func TestParseFormatRefusesUnbalancedBraces(t *testing.T) {
+	for _, format := range []string{"{a", "a}", "{a{b}}", "{f(}"} {
+		if _, err := ParseFormat(format, nil); err == nil {
+			t.Errorf("ParseFormat(%q) = nil error, want one", format)
+		}
+	}
+}