Compile format strings at New instead of re-scanning them on every render

bench_test.go

@@ -0,0 +1,72 @@
+package fakes
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func benchFaker(b *testing.B, dir string) *Fakes {
+	b.Helper()
+	f, err := New([]string{dir}, WithSeed(1))
+	if err != nil {
+		b.Fatal(err)
+	}
+	return f
+}
+
+func benchPath(b *testing.B, dir, path string) {
+	f := benchFaker(b, dir)
+	b.ReportAllocs()
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		if _, err := f.Fake(path); err != nil {
+			b.Fatal(err)
+		}
+	}
+}
+
+func BenchmarkPerson(b *testing.B)     { benchPath(b, "data/sv_SE", "person") }
+func BenchmarkAddress(b *testing.B)    { benchPath(b, "data/sv_SE", "address") }
+func BenchmarkWord(b *testing.B)       { benchPath(b, "data/sv_SE", "word") }
+func BenchmarkCreditcard(b *testing.B) { benchPath(b, "data/misc", "creditcard") }
+func BenchmarkSSN(b *testing.B)        { benchPath(b, "data/sv_SE", "ssn") }
+func BenchmarkUUIDv7(b *testing.B)     { benchPath(b, "data/misc", "uuid") }
+
+// tmpData writes one category JSON into a fresh dir and returns the dir.
+func tmpData(b *testing.B, name, body string) string {
+	b.Helper()
+	dir := b.TempDir()
+	if err := os.WriteFile(filepath.Join(dir, name+".json"), []byte(body), 0o644); err != nil {
+		b.Fatal(err)
+	}
+	return dir
+}
+
+// BenchmarkCalc exercises the per-render expression re-parse.
+func BenchmarkCalc(b *testing.B) {
+	dir := tmpData(b, "inv", `{"format":"{net} x {qty} = {calc(net * qty, 2)}","net":["19.99"],"qty":["3"]}`)
+	benchPath(b, dir, "inv")
+}
+
+// BenchmarkLongLiteral exercises the per-rune literal write path.
+func BenchmarkLongLiteral(b *testing.B) {
+	dir := tmpData(b, "sql", `{"format":"INSERT INTO customers (id, name, city) V#ALUES (#1#2#3, '{word}', '{word}');","word":["alpha","beta","gamma","delta"]}`)
+	benchPath(b, dir, "sql")
+}
+
+// BenchmarkRepeat exercises repeat + separator.
+func BenchmarkRepeat(b *testing.B) {
+	dir := tmpData(b, "many", `{"format":"{word}","repeat":20,"separator":", ","word":["alpha","beta","gamma","delta"]}`)
+	benchPath(b, dir, "many")
+}
+
+// BenchmarkNew measures load+compile+validate of the whole shipped tree.
+func BenchmarkNew(b *testing.B) {
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		if _, err := New([]string{"data"}, WithSeed(1)); err != nil {
+			b.Fatal(err)
+		}
+	}
+}