golang.org/x/text v0.3.2: charmap.ISO8859_1

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 charmap.ISO8859_1 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:
  - charmap.ISO8859_1
Constraints:
  - executionContext: node
Required runtime conditions:
  - ecosystem: npm
  - language: javascript
  - moduleSystem: cjs
  - packageManager: npm@10.9.8
  - runtime: node@22.23.2

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:sha256:4c5a432ff726c5148bc36c6e1cf203bc4010d664c09b57f01262c038e04d7203","contract":["charmap.ISO8859_1 encodes UTF-8 text containing accented Latin-1 characters into single-byte ISO-8859-1 representation","charmap.ISO8859_1 decodes single-byte Latin-1 encoded bytes back to the original UTF-8 text","charmap.ISO8859_1 encoder returns an error for characters outside the Latin-1 range"],"goal":"verify charmap.ISO8859_1 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":["charmap.ISO8859_1"]},"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":["charmap.ISO8859_1"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.22

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=

package main

import (
	"fmt"
	"os"

	"golang.org/x/text/encoding/charmap"
)

func main() {
	encoder := charmap.ISO8859_1.NewEncoder()
	decoder := charmap.ISO8859_1.NewDecoder()

	original := "café résumé niño"
	encoded, err := encoder.String(original)
	if err != nil {
		fmt.Fprintf(os.Stderr, "Encoding failed: %v\n", err)
		os.Exit(1)
	}

	decoded, err := decoder.String(encoded)
	if err != nil {
		fmt.Fprintf(os.Stderr, "Decoding failed: %v\n", err)
		os.Exit(1)
	}

	fmt.Printf("Original: %s\n", original)
	fmt.Printf("Encoded length (bytes): %d\n", len(encoded))
	fmt.Printf("Decoded: %s\n", decoded)
}

{
  "schemaVersion": 1,
  "goal": "verify charmap.ISO8859_1 in pkg:golang/golang.org/x/text@v0.3.2",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/text@v0.3.2"
  ],
  "symbols": [
    "charmap.ISO8859_1"
  ],
  "constraints": {
    "executionContext": "node"
  },
  "runtimeConditions": {
    "ecosystem": "npm",
    "language": "javascript",
    "moduleSystem": "cjs",
    "packageManager": "npm@10.9.8",
    "runtime": "node@22.23.2"
  }
}

package main

import (
	"bytes"
	"fmt"
	"os"

	"golang.org/x/text/encoding/charmap"
)

func main() {
	encoder := charmap.ISO8859_1.NewEncoder()
	decoder := charmap.ISO8859_1.NewDecoder()

	// Assertion 1: charmap.ISO8859_1 encodes UTF-8 text containing accented Latin-1 characters into single-byte ISO-8859-1 representation
	src := "café résumé niño"
	encoded, err := encoder.Bytes([]byte(src))
	if err != nil {
		fmt.Fprintf(os.Stderr, "FAIL: ISO8859_1 encode error: %v\n", err)
		os.Exit(1)
	}

	// In UTF-8, "café résumé niño" is 19 bytes (accented chars é, é, é, ñ are 2 bytes each).
	// In ISO-8859-1, every character is exactly 1 byte -> 16 bytes total.
	if len(encoded) != 16 {
		fmt.Fprintf(os.Stderr, "FAIL: expected 16 bytes in ISO-8859-1, got %d\n", len(encoded))
		os.Exit(1)
	}
	// 'c'(0), 'a'(1), 'f'(2), 'é'(3), ' '(4), 'r'(5), 'é'(6), 's'(7), 'u'(8), 'm'(9), 'é'(10), ' '(11), 'n'(12), 'i'(13), 'ñ'(14), 'o'(15)
	// 'é' is 0xE9 (byte 233), 'ñ' is 0xF1 (byte 241)
	if encoded[3] != 0xE9 || encoded[6] != 0xE9 || encoded[10] != 0xE9 || encoded[14] != 0xF1 {
		fmt.Fprintf(os.Stderr, "FAIL: incorrect Latin-1 byte mapping in encoded bytes: %v\n", encoded)
		os.Exit(1)
	}

	// Assertion 2: charmap.ISO8859_1 decodes single-byte Latin-1 encoded bytes back to the original UTF-8 text
	decoded, err := decoder.Bytes(encoded)
	if err != nil {
		fmt.Fprintf(os.Stderr, "FAIL: ISO8859_1 decode error: %v\n", err)
		os.Exit(1)
	}
	if !bytes.Equal(decoded, []byte(src)) {
		fmt.Fprintf(os.Stderr, "FAIL: decoded mismatch: got %q, want %q\n", string(decoded), src)
		os.Exit(1)
	}

	// Assertion 3: charmap.ISO8859_1 encoder returns an error for characters outside the Latin-1 range
	_, err = encoder.Bytes([]byte("Price: 10 €"))
	if err == nil {
		fmt.Fprintf(os.Stderr, "FAIL: expected error encoding character outside Latin-1, got nil\n")
		os.Exit(1)
	}

	fmt.Println("PASS: charmap.ISO8859_1 contract verified")
}