golang.org/x/text v0.3.2: cases.Lower

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 cases.Lower in pkg:golang/golang.org/x/text@v0.3.2
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/golang.org/x/text@v0.3.2
Demonstrate these symbols/APIs:
  - cases.Lower

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 textcases

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

// Lowercase converts a string to lowercase using the specified language tag and options.
func Lowercase(tag language.Tag, s string, opts ...cases.Option) string {
	return cases.Lower(tag, opts...).String(s)
}

// LowercaseBytes converts a byte slice to lowercase using the specified language tag and options.
func LowercaseBytes(tag language.Tag, b []byte, opts ...cases.Option) []byte {
	return cases.Lower(tag, opts...).Bytes(b)
}

{"case":{"caseId":"case:sha256:c90e6cea74affaf40569543db3dc418b98c99bd52aec359a9b4e066e67d377bd","contract":["cases.Lower performs language-specific lowercase transformation on strings and byte slices","cases.Lower respects Turkish dotted and dotless I distinctions","cases.Lower handles Greek final sigma mapping with optional HandleFinalSigma toggle"],"goal":"verify cases.Lower in pkg:golang/golang.org/x/text@v0.3.2","kind":"HOW","packages":["pkg:golang/golang.org/x/text@v0.3.2"],"schemaVersion":1,"symbols":["cases.Lower"]},"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@v0.3.2"],"schemaVersion":1,"subject":"pkg:golang/golang.org/x/text@v0.3.2","symbols":["cases.Lower"],"verifierAdapter":"golang@1"}

module example.com/cases-sample

go 1.26.6

require golang.org/x/text v0.3.2

golang.org/x/text v0.3.2 h1:tW2bmiBqwgJj/UpqtC8EpXEZVYOwU0yG4iWbprSVAcs=
golang.org/x/text v0.3.2/go.mod h1:bEr9sfX3Q8Zfm5fL9x+3itogRgK3+ptLWKqgva+5dAk=
golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=

{
  "schemaVersion": 1,
  "goal": "verify cases.Lower in pkg:golang/golang.org/x/text@v0.3.2",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/text@v0.3.2"
  ],
  "symbols": [
    "cases.Lower"
  ]
}

package main

import (
	"bytes"
	"fmt"
	"os"

	textcases "example.com/cases-sample"
	"golang.org/x/text/cases"
	"golang.org/x/text/language"
)

func main() {
	// Assertion 1: Basic lowercase transformation with language.Und
	undCaser := cases.Lower(language.Und)
	if got := undCaser.String("HELLO WORLD"); got != "hello world" {
		fmt.Fprintf(os.Stderr, "FAIL: expected 'hello world', got %q\n", got)
		os.Exit(1)
	}

	// Assertion 2: Byte slice transformation with Bytes()
	inputBytes := []byte("DATA STREAM")
	expectedBytes := []byte("data stream")
	if got := undCaser.Bytes(inputBytes); !bytes.Equal(got, expectedBytes) {
		fmt.Fprintf(os.Stderr, "FAIL: expected %q, got %q\n", expectedBytes, got)
		os.Exit(1)
	}

	// Assertion 3: Turkish language casing (dotted and dotless I)
	// 'I' (U+0049) -> 'ı' (U+0131, Latin small letter dotless i)
	// 'İ' (U+0130, Latin capital letter I with dot above) -> 'i' (U+0069)
	trCaser := cases.Lower(language.Turkish)
	if got := trCaser.String("ISTANBUL"); got != "ıstanbul" {
		fmt.Fprintf(os.Stderr, "FAIL: Turkish 'ISTANBUL' expected 'ıstanbul', got %q\n", got)
		os.Exit(1)
	}
	if got := trCaser.String("İĞNE"); got != "iğne" {
		fmt.Fprintf(os.Stderr, "FAIL: Turkish 'İĞNE' expected 'iğne', got %q\n", got)
		os.Exit(1)
	}

	// Assertion 4: Greek final sigma handling
	// Capital sigma 'Σ' at end of word becomes 'ς' (U+03C2, final sigma).
	// In the middle or start of word it becomes 'σ' (U+03C3).
	// "ΟΔΥΣΣΕΥΣ" -> "οδυσσευς"
	elCaser := cases.Lower(language.Greek)
	elGot := elCaser.String("ΟΔΥΣΣΕΥΣ")
	elRunes := []rune(elGot)
	if len(elRunes) == 0 || elRunes[len(elRunes)-1] != '\u03c2' {
		fmt.Fprintf(os.Stderr, "FAIL: Greek 'ΟΔΥΣΣΕΥΣ' expected final sigma '\\u03c2', got %q\n", elGot)
		os.Exit(1)
	}

	// Assertion 5: Greek casing with HandleFinalSigma(false)
	// When final sigma handling is disabled, 'Σ' at the end remains 'σ' (U+03C3).
	elNoFinalCaser := cases.Lower(language.Greek, cases.HandleFinalSigma(false))
	elNoFinalGot := elNoFinalCaser.String("ΟΔΥΣΣΕΥΣ")
	elNoFinalRunes := []rune(elNoFinalGot)
	if len(elNoFinalRunes) == 0 || elNoFinalRunes[len(elNoFinalRunes)-1] != '\u03c3' {
		fmt.Fprintf(os.Stderr, "FAIL: Greek with HandleFinalSigma(false) expected regular sigma '\\u03c3', got %q\n", elNoFinalGot)
		os.Exit(1)
	}

	// Assertion 6: Helper function Lowercase and LowercaseBytes
	if got := textcases.Lowercase(language.English, "Go Language"); got != "go language" {
		fmt.Fprintf(os.Stderr, "FAIL: helper Lowercase expected 'go language', got %q\n", got)
		os.Exit(1)
	}
	if got := textcases.LowercaseBytes(language.English, []byte("GOPHER")); !bytes.Equal(got, []byte("gopher")) {
		fmt.Fprintf(os.Stderr, "FAIL: helper LowercaseBytes expected 'gopher', got %q\n", got)
		os.Exit(1)
	}

	fmt.Println("PASS: cases.Lower contract passed")
}