golang.org/x/tools v0.1.1: txtar.File

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/tools/txtar.File in pkg:golang/golang.org/x/tools@v0.1.1
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/golang.org/x/tools@v0.1.1
Demonstrate these symbols/APIs:
  - golang.org/x/tools/txtar.File

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:sha256:24ad8de284a096d761a3a2c68e051c0230c0bc0729d4c7f37a621aa21214104f","contract":["txtar.File stores a file Name and byte slice Data within a txtar.Archive","txtar.Parse parses txtar-formatted bytes into a comment and a slice of txtar.File entries","txtar.Format serializes a txtar.Archive and its txtar.File entries, appending a trailing newline to non-empty file data if missing","txtar.Format and txtar.Parse roundtrip txtar.File entries including empty and nested path files"],"goal":"verify golang.org/x/tools/txtar.File in pkg:golang/golang.org/x/tools@v0.1.1","kind":"HOW","packages":["pkg:golang/golang.org/x/tools@v0.1.1"],"schemaVersion":1,"symbols":["golang.org/x/tools/txtar.File"]},"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/tools@v0.1.1"],"schemaVersion":1,"subject":"pkg:golang/golang.org/x/tools@v0.1.1","symbols":["golang.org/x/tools/txtar.File"],"verifierAdapter":"golang@1"}

module sample

go 1.21

require golang.org/x/tools v0.1.1

golang.org/x/tools v0.1.1 h1:wGiQel/hW0NnEkJUk8lbzkX2gFJU6PFxf1v5OlCfuOs=
golang.org/x/tools v0.1.1/go.mod h1:o0xws9oXOQQZyjljx8fwUC0k7L1pTE6eaCbjGeHmOkk=

{
  "schemaVersion": 1,
  "goal": "verify golang.org/x/tools/txtar.File in pkg:golang/golang.org/x/tools@v0.1.1",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/tools@v0.1.1"
  ],
  "symbols": [
    "golang.org/x/tools/txtar.File"
  ]
}

package main

import (
	"bytes"
	"fmt"
	"os"

	"golang.org/x/tools/txtar"
)

func main() {
	if err := verifyTxtarFile(); err != nil {
		fmt.Fprintf(os.Stderr, "Contract test failed: %v\n", err)
		os.Exit(1)
	}
	fmt.Println("All contract assertions passed.")
}

func verifyTxtarFile() error {
	// 1. Direct construction of txtar.File with Name and Data fields
	f := txtar.File{
		Name: "hello.txt",
		Data: []byte("world\n"),
	}
	if f.Name != "hello.txt" || !bytes.Equal(f.Data, []byte("world\n")) {
		return fmt.Errorf("unexpected txtar.File fields: %+v", f)
	}

	// 2. txtar.Parse extracts multiple txtar.File entries and separates archive comments
	raw := []byte("header comment\n-- file1.txt --\nline1\n-- dir/file2.txt --\nlineA\nlineB\n")
	arch := txtar.Parse(raw)
	if string(arch.Comment) != "header comment\n" {
		return fmt.Errorf("unexpected comment: %q", string(arch.Comment))
	}
	if len(arch.Files) != 2 {
		return fmt.Errorf("expected 2 files, got %d", len(arch.Files))
	}
	if arch.Files[0].Name != "file1.txt" || string(arch.Files[0].Data) != "line1\n" {
		return fmt.Errorf("unexpected file[0]: %+v", arch.Files[0])
	}
	if arch.Files[1].Name != "dir/file2.txt" || string(arch.Files[1].Data) != "lineA\nlineB\n" {
		return fmt.Errorf("unexpected file[1]: %+v", arch.Files[1])
	}

	// 3. txtar.Format serializes txtar.Archive with txtar.File entries, including missing trailing newline fixup
	customArch := &txtar.Archive{
		Comment: []byte("archive note\n"),
		Files: []txtar.File{
			{Name: "no-newline.txt", Data: []byte("content without newline")},
			{Name: "empty.txt", Data: nil},
		},
	}
	formatted := txtar.Format(customArch)
	expected := "archive note\n-- no-newline.txt --\ncontent without newline\n-- empty.txt --\n"
	if string(formatted) != expected {
		return fmt.Errorf("format mismatch:\ngot:  %q\nwant: %q", string(formatted), expected)
	}

	// 4. Roundtrip txtar.Format and txtar.Parse preserves txtar.File entries
	reparsed := txtar.Parse(formatted)
	if len(reparsed.Files) != 2 {
		return fmt.Errorf("roundtrip expected 2 files, got %d", len(reparsed.Files))
	}
	if reparsed.Files[0].Name != "no-newline.txt" || string(reparsed.Files[0].Data) != "content without newline\n" {
		return fmt.Errorf("roundtrip file[0] mismatch: %+v", reparsed.Files[0])
	}
	if reparsed.Files[1].Name != "empty.txt" || len(reparsed.Files[1].Data) != 0 {
		return fmt.Errorf("roundtrip file[1] mismatch: %+v", reparsed.Files[1])
	}

	return nil
}