golang.org/x/text v0.29.0: convert text to title case using language-specific casing rules

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: convert text to title case using language-specific casing rules
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/golang.org/x/text@v0.29.0
Demonstrate these symbols/APIs:
  - golang.org/x/text/cases.Title
  - golang.org/x/text/language.Tag

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

package casing

import (
	"golang.org/x/text/cases"
	"golang.org/x/text/language"
)

// ToTitle converts a string to title case using the specified language tag rules.
func ToTitle(tag language.Tag, s string) string {
	c := cases.Title(tag)
	return c.String(s)
}

// ToUpper converts a string to upper case using the specified language tag rules.
func ToUpper(tag language.Tag, s string) string {
	c := cases.Upper(tag)
	return c.String(s)
}

// ToLower converts a string to lower case using the specified language tag rules.
func ToLower(tag language.Tag, s string) string {
	c := cases.Lower(tag)
	return c.String(s)
}

{"case":{"caseId":"case:sha256:328701b1b5d5733033474f331bc1a028be2daffa952977c23d5acfdd7b4f77d3","contract":["cases.Title(language.English).String(\"the lord of the rings\") == \"The Lord Of The Rings\"","cases.Title(language.Turkish).String(\"istanbul\") == \"İstanbul\"","cases.Title(language.Dutch).String(\"ijsselmeer\") == \"IJsselmeer\"","cases.Upper(language.Turkish).String(\"diyarbakır\") == \"DİYARBAKIR\""],"goal":"convert text to title case using language-specific casing rules","kind":"HOW","packages":["pkg:golang/golang.org/x/text@v0.29.0"],"schemaVersion":1,"symbols":["golang.org/x/text/cases.Title","golang.org/x/text/language.Tag"]},"contractCommand":["go","run","./test"],"environment":{"arch":"x64","ecosystem":"golang","os":"windows","osVersionBucket":"11","packageManager":"go","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/golang.org/x/text@v0.29.0"],"schemaVersion":1,"symbols":["golang.org/x/text/cases.Title","golang.org/x/text/language.Tag"],"verifierAdapter":"golang@1"}

module example.com/casing

go 1.24.0

require golang.org/x/text v0.29.0

golang.org/x/text v0.29.0 h1:1neNs90w9YzJ9BocxfsQNHKuAT4pkghyXc4nhZ6sJvk=
golang.org/x/text v0.29.0/go.mod h1:7MhJOA9CD2qZyOKYazxdYMF85OwPdEr9jTtBpO7ydH4=

{
  "schemaVersion": 1,
  "goal": "convert text to title case using language-specific casing rules",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/text@v0.29.0"
  ],
  "symbols": [
    "golang.org/x/text/cases.Title",
    "golang.org/x/text/language.Tag"
  ]
}

package main

import (
	"fmt"
	"os"

	"example.com/casing"
	"golang.org/x/text/cases"
	"golang.org/x/text/language"
)

func assertEqual(got, want, context string) {
	if got != want {
		fmt.Fprintf(os.Stderr, "Assertion failed for %s: got %q, want %q\n", context, got, want)
		os.Exit(1)
	}
}

func main() {
	// English title casing
	enTitle := casing.ToTitle(language.English, "the lord of the rings")
	assertEqual(enTitle, "The Lord Of The Rings", "English title casing")

	// Direct cases.Title with language.English
	enDirect := cases.Title(language.English).String("hello world")
	assertEqual(enDirect, "Hello World", "Direct cases.Title with English")

	// Turkish title casing: 'i' becomes dotted capital 'İ'
	trTitle := casing.ToTitle(language.Turkish, "istanbul")
	assertEqual(trTitle, "İstanbul", "Turkish title casing for 'istanbul'")

	// Dutch title casing: 'ij' digraph capitalized together as 'IJ'
	nlTitle := casing.ToTitle(language.Dutch, "ijsselmeer")
	assertEqual(nlTitle, "IJsselmeer", "Dutch title casing for 'ijsselmeer'")

	// English upper casing
	enUpper := casing.ToUpper(language.English, "hello")
	assertEqual(enUpper, "HELLO", "English upper casing")

	// Turkish upper casing: 'i' becomes 'İ'
	trUpper := casing.ToUpper(language.Turkish, "diyarbakır")
	assertEqual(trUpper, "DİYARBAKIR", "Turkish upper casing for 'diyarbakır'")

	fmt.Println("All contract assertions passed.")
}