golang.org/x/text v0.26.0: cases.Title, language.Parse, norm.NFC

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: verify pkg:golang/golang.org/x/text@v0.26.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/golang.org/x/text@v0.26.0

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.

{"case":{"caseId":"case:sha256:3d1560c396e59c666570675c17ce62f73f379cca562f83ea314b3a2008e3639a","contract":["language.Parse parses valid BCP 47 language tags and returns an error on malformed tags","norm.NFC composes decomposed NFD rune sequences into canonical NFC form and reports normalization status via IsNormalString","cases.Title converts strings to title case using language-specific rules including Turkish dotted I, Dutch IJ, and cases.NoLower","transform.Chain pipelines norm.NFC and cases transformers across strings via transform.String"],"goal":"verify pkg:golang/golang.org/x/text@v0.26.0","kind":"HOW","packages":["pkg:golang/golang.org/x/text@v0.26.0"],"schemaVersion":1,"symbols":["cases.Title","language.Parse","norm.NFC","transform.Chain"]},"contractCommand":["go","run","./test"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"golang","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"go","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/golang.org/x/text@v0.26.0"],"schemaVersion":1,"subject":"pkg:golang/golang.org/x/text@v0.26.0","symbols":["cases.Title","language.Parse","norm.NFC","transform.Chain"],"verifierAdapter":"golang@1"}

module example.com/text-sample

go 1.26.6

require golang.org/x/text v0.26.0

golang.org/x/text v0.26.0 h1:P42AVeLghgTYr4+xUnTRKDMqpar+PtX7KWuNQL21L8M=
golang.org/x/text v0.26.0/go.mod h1:QK15LZJUUQVJxhz7wXgxSy/CJaTFjd0G+YLonydOVQA=

{
  "schemaVersion": 1,
  "goal": "verify pkg:golang/golang.org/x/text@v0.26.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/text@v0.26.0"
  ]
}

package main

import (
	"fmt"
	"os"

	textsample "example.com/text-sample"
	"golang.org/x/text/cases"
	"golang.org/x/text/language"
	"golang.org/x/text/transform"
	"golang.org/x/text/unicode/norm"
)

func main() {
	// Assertion 1: language.Parse parses valid BCP 47 language tags and rejects invalid ones
	trTag, err := language.Parse("tr-TR")
	if err != nil || trTag != language.MustParse("tr-TR") {
		fmt.Fprintf(os.Stderr, "FAIL: language.Parse('tr-TR') unexpected result: tag=%v, err=%v\n", trTag, err)
		os.Exit(1)
	}
	if _, err := language.Parse("invalid_tag_!!!"); err == nil {
		fmt.Fprintln(os.Stderr, "FAIL: language.Parse should fail on malformed tag")
		os.Exit(1)
	}

	// Assertion 2: norm.NFC composes decomposed NFD rune sequences into canonical NFC form
	nfdInput := "e\u0301cole" // 'e' + combining acute accent
	nfcExpected := "\u00e9cole"
	if norm.NFC.IsNormalString(nfdInput) {
		fmt.Fprintln(os.Stderr, "FAIL: expected NFD input to report false for NFC.IsNormalString")
		os.Exit(1)
	}
	nfcOut := norm.NFC.String(nfdInput)
	if nfcOut != nfcExpected || !norm.NFC.IsNormalString(nfcOut) {
		fmt.Fprintf(os.Stderr, "FAIL: norm.NFC.String expected %q, got %q\n", nfcExpected, nfcOut)
		os.Exit(1)
	}

	// Assertion 3: cases.Title applies language-specific title casing rules (Turkish dotted I and Dutch IJ)
	if got := cases.Title(language.Turkish).String("istanbul ılık"); got != "İstanbul Ilık" {
		fmt.Fprintf(os.Stderr, "FAIL: Turkish title case expected 'İstanbul Ilık', got %q\n", got)
		os.Exit(1)
	}
	if got := cases.Title(language.Dutch).String("ijsland"); got != "IJsland" {
		fmt.Fprintf(os.Stderr, "FAIL: Dutch title case expected 'IJsland', got %q\n", got)
		os.Exit(1)
	}
	if got := cases.Title(language.Und, cases.NoLower).String("hELLO wORLD"); got != "HELLO WORLD" {
		fmt.Fprintf(os.Stderr, "FAIL: cases.NoLower expected 'HELLO WORLD', got %q\n", got)
		os.Exit(1)
	}

	// Assertion 4: transform.Chain pipelines norm.NFC and cases.Title through NormalizeAndTitle
	chainedOut, parsedTag, err := textsample.NormalizeAndTitle("fr", "e\u0301cole normale")
	if err != nil {
		fmt.Fprintf(os.Stderr, "FAIL: NormalizeAndTitle unexpected error: %v\n", err)
		os.Exit(1)
	}
	if parsedTag != language.French {
		fmt.Fprintf(os.Stderr, "FAIL: expected French tag, got %v\n", parsedTag)
		os.Exit(1)
	}
	if chainedOut != "\u00c9cole Normale" {
		fmt.Fprintf(os.Stderr, "FAIL: expected '\\u00c9cole Normale', got %q\n", chainedOut)
		os.Exit(1)
	}

	// Verify direct transform.String with transform.Chain on byte/string streams
	directChain := transform.Chain(norm.NFC, cases.Upper(language.Turkish))
	upperOut, _, err := transform.String(directChain, "izmu\u0308r")
	if err != nil || upperOut != "İZMÜR" {
		fmt.Fprintf(os.Stderr, "FAIL: direct transform.Chain expected 'İZMÜR', got %q (err=%v)\n", upperOut, err)
		os.Exit(1)
	}

	fmt.Println("PASS: golang.org/x/text@v0.26.0 contract passed")
}

package textsample

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

// NormalizeAndTitle parses a BCP 47 language tag and applies NFC normalization
// followed by language-aware title casing via a chained transformer.
func NormalizeAndTitle(langTag string, input string, opts ...cases.Option) (string, language.Tag, error) {
	tag, err := language.Parse(langTag)
	if err != nil {
		return "", language.Und, err
	}
	chain := transform.Chain(norm.NFC, cases.Title(tag, opts...))
	out, _, err := transform.String(chain, input)
	if err != nil {
		return "", tag, err
	}
	return out, tag, nil
}