golang.org/x/text v0.16.0: language.Tag

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 golang.org/x/text/language.Tag in pkg:golang/golang.org/x/text@v0.16.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/golang.org/x/text@v0.16.0
Demonstrate these symbols/APIs:
  - 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.

{"case":{"caseId":"case:sha256:61b8b804fb8de832d64d677d3d49caf7f9ef26a5b6aa1b73b976d5d3745c5182","contract":["language.Parse parses valid BCP 47 language tag into Tag","language.Parse returns error for invalid BCP 47 tag","Tag.String returns canonical BCP 47 string representation","Tag.Base decomposes to expected base language with exact confidence","Tag.Region decomposes to expected region with exact confidence","Tag.Parent returns parent Tag in language hierarchy","Tag.IsRoot returns true for Und and false for concrete language tags","Tag values are comparable for equality"],"goal":"verify golang.org/x/text/language.Tag in pkg:golang/golang.org/x/text@v0.16.0","kind":"HOW","packages":["pkg:golang/golang.org/x/text@v0.16.0"],"schemaVersion":1,"symbols":["golang.org/x/text/language.Tag"]},"contractCommand":["go","run","./test"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"golang","language":"go","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"go","packageManagerVersion":"1.26.6","runtime":"go","runtimeVersion":"1.26.6","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/golang.org/x/text@v0.16.0"],"schemaVersion":1,"subject":"pkg:golang/golang.org/x/text@v0.16.0","symbols":["golang.org/x/text/language.Tag"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.26.0

require golang.org/x/text v0.16.0

golang.org/x/text v0.16.0 h1:a94ExnEXNtEwYLGJSIUxnWoxoRz/ZcCsV63ROupILh4=
golang.org/x/text v0.16.0/go.mod h1:GhwF1Be+LQoKShO3cGOHzqOgRrGaYc9AvblQOmPVHnI=

package main

import (
	"fmt"

	"golang.org/x/text/language"
)

func main() {
	// Parse a BCP 47 language tag into a language.Tag
	tag, err := language.Parse("fr-CA")
	if err != nil {
		fmt.Printf("Error parsing tag: %v\n", err)
		return
	}

	fmt.Printf("Tag string: %s\n", tag.String())

	base, confBase := tag.Base()
	fmt.Printf("Base language: %s (confidence: %v)\n", base.String(), confBase)

	region, confRegion := tag.Region()
	fmt.Printf("Region: %s (confidence: %v)\n", region.String(), confRegion)

	parent := tag.Parent()
	fmt.Printf("Parent tag: %s\n", parent.String())

	fmt.Printf("Is root: %t\n", tag.IsRoot())
}

{
  "schemaVersion": 1,
  "goal": "verify golang.org/x/text/language.Tag in pkg:golang/golang.org/x/text@v0.16.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/text@v0.16.0"
  ],
  "symbols": [
    "golang.org/x/text/language.Tag"
  ]
}

package main

import (
	"fmt"
	"os"

	"golang.org/x/text/language"
)

func main() {
	// Assertion 1: language.Parse parses valid BCP 47 language tag into Tag
	tag, err := language.Parse("fr-CA")
	if err != nil {
		fmt.Fprintf(os.Stderr, "assertion 1 failed: language.Parse(\"fr-CA\") error: %v\n", err)
		os.Exit(1)
	}

	// Assertion 2: language.Parse returns error for invalid BCP 47 tag
	if _, err := language.Parse("invalid_tag_format_123456789"); err == nil {
		fmt.Fprintf(os.Stderr, "assertion 2 failed: expected error for invalid tag, got nil\n")
		os.Exit(1)
	}

	// Assertion 3: Tag.String returns canonical BCP 47 string representation
	if got := tag.String(); got != "fr-CA" {
		fmt.Fprintf(os.Stderr, "assertion 3 failed: tag.String() = %q, want %q\n", got, "fr-CA")
		os.Exit(1)
	}

	// Assertion 4: Tag.Base decomposes to expected base language with exact confidence
	base, confBase := tag.Base()
	if base.String() != "fr" || confBase != language.Exact {
		fmt.Fprintf(os.Stderr, "assertion 4 failed: base = %q, conf = %v\n", base.String(), confBase)
		os.Exit(1)
	}

	// Assertion 5: Tag.Region decomposes to expected region with exact confidence
	region, confRegion := tag.Region()
	if region.String() != "CA" || confRegion != language.Exact {
		fmt.Fprintf(os.Stderr, "assertion 5 failed: region = %q, conf = %v\n", region.String(), confRegion)
		os.Exit(1)
	}

	// Assertion 6: Tag.Parent returns parent Tag in language hierarchy
	parent := tag.Parent()
	if parent.String() != "fr" {
		fmt.Fprintf(os.Stderr, "assertion 6 failed: parent = %q, want %q\n", parent.String(), "fr")
		os.Exit(1)
	}

	// Assertion 7: Tag.IsRoot returns true for Und and false for concrete language tags
	if !language.Und.IsRoot() {
		fmt.Fprintf(os.Stderr, "assertion 7 failed: Und.IsRoot() = false, want true\n")
		os.Exit(1)
	}
	if tag.IsRoot() {
		fmt.Fprintf(os.Stderr, "assertion 7 failed: tag.IsRoot() = true, want false\n")
		os.Exit(1)
	}

	// Assertion 8: Tag values are comparable for equality
	tagA := language.Make("fr-CA")
	tagB := language.Make("fr-CA")
	tagC := language.Make("en-US")
	if tagA != tagB {
		fmt.Fprintf(os.Stderr, "assertion 8 failed: tagA != tagB\n")
		os.Exit(1)
	}
	if tagA == tagC {
		fmt.Fprintf(os.Stderr, "assertion 8 failed: tagA == tagC\n")
		os.Exit(1)
	}

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