go.yaml.in/yaml/v3 v3.0.5: Node

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/go.yaml.in/yaml/v3@v3.0.5
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/go.yaml.in/yaml/v3@v3.0.5
Demonstrate these symbols/APIs:
  - Node

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 sample

import (
	"bytes"
	"strings"
	"testing"

	"go.yaml.in/yaml/v3"
)

type ServerConfig struct {
	Host string `yaml:"host"`
	Port int    `yaml:"port"`
}

func TestNodeASTParsing(t *testing.T) {
	raw := `
# Server configuration
host: localhost # primary host
port: 8080
`
	var root yaml.Node
	if err := yaml.Unmarshal([]byte(raw), &root); err != nil {
		t.Fatalf("yaml.Unmarshal failed: %v", err)
	}

	if root.Kind != yaml.DocumentNode {
		t.Fatalf("expected DocumentNode, got %v", root.Kind)
	}
	if len(root.Content) != 1 {
		t.Fatalf("expected 1 document child, got %d", len(root.Content))
	}

	mapping := root.Content[0]
	if mapping.Kind != yaml.MappingNode {
		t.Fatalf("expected MappingNode, got %v", mapping.Kind)
	}
	// Mapping node has alternating key and value nodes
	if len(mapping.Content) != 4 {
		t.Fatalf("expected 4 mapping entries (2 pairs), got %d", len(mapping.Content))
	}

	keyHost := mapping.Content[0]
	valHost := mapping.Content[1]
	if keyHost.Kind != yaml.ScalarNode || valHost.Kind != yaml.ScalarNode {
		t.Errorf("expected ScalarNodes for host pair, got %v and %v", keyHost.Kind, valHost.Kind)
	}
	if keyHost.Value != "host" || valHost.Value != "localhost" {
		t.Errorf("expected host: localhost, got %s: %s", keyHost.Value, valHost.Value)
	}
}

func TestNodeCommentPreservation(t *testing.T) {
	raw := `
# Header comment
service: auth # inline comment
`
	var root yaml.Node
	if err := yaml.Unmarshal([]byte(raw), &root); err != nil {
		t.Fatalf("yaml.Unmarshal failed: %v", err)
	}

	mapping := root.Content[0]
	keyService := mapping.Content[0]
	valService := mapping.Content[1]

	if !strings.Contains(keyService.HeadComment, "Header comment") {
		t.Errorf("expected HeadComment to contain 'Header comment', got %q", keyService.HeadComment)
	}
	if !strings.Contains(valService.LineComment, "inline comment") {
		t.Errorf("expected LineComment to contain 'inline comment', got %q", valService.LineComment)
	}
}

func TestNodeDecode(t *testing.T) {
	raw := `
host: 127.0.0.1
port: 9090
`
	var root yaml.Node
	if err := yaml.Unmarshal([]byte(raw), &root); err != nil {
		t.Fatalf("yaml.Unmarshal failed: %v", err)
	}

	mapping := root.Content[0]
	var cfg ServerConfig
	if err := mapping.Decode(&cfg); err != nil {
		t.Fatalf("mapping.Decode failed: %v", err)
	}

	if cfg.Host != "127.0.0.1" || cfg.Port != 9090 {
		t.Fatalf("expected cfg {127.0.0.1, 9090}, got %+v", cfg)
	}
}

func TestNodeEncode(t *testing.T) {
	cfg := ServerConfig{
		Host: "example.internal",
		Port: 443,
	}

	var node yaml.Node
	if err := node.Encode(&cfg); err != nil {
		t.Fatalf("node.Encode failed: %v", err)
	}

	if node.Kind != yaml.MappingNode {
		t.Fatalf("expected MappingNode from Encode, got %v", node.Kind)
	}

	var buf bytes.Buffer
	enc := yaml.NewEncoder(&buf)
	if err := enc.Encode(&node); err != nil {
		t.Fatalf("enc.Encode failed: %v", err)
	}
	if err := enc.Close(); err != nil {
		t.Fatalf("enc.Close failed: %v", err)
	}

	out := buf.String()
	if !strings.Contains(out, "host: example.internal") {
		t.Errorf("expected 'host: example.internal' in encoded yaml, got:\n%s", out)
	}
	if !strings.Contains(out, "port: 443") {
		t.Errorf("expected 'port: 443' in encoded yaml, got:\n%s", out)
	}
}

{"case":{"caseId":"case:sha256:612d95d0ac81830a215f99b807e5433a59960fb2be0aca94024599f31cb4ff40","contract":["yaml.Node parses YAML document hierarchy into DocumentNode, MappingNode, and ScalarNode AST","yaml.Node preserves comments including HeadComment and LineComment on child nodes","yaml.Node Decode unmarshals mapping node content directly into target Go struct fields","yaml.Node Encode serializes Go struct values into a Node AST hierarchy"],"goal":"verify pkg:golang/go.yaml.in/yaml/v3@v3.0.5","kind":"HOW","packages":["pkg:golang/go.yaml.in/yaml/v3@v3.0.5"],"schemaVersion":1,"symbols":["Node"]},"contractCommand":["go","test","-v","./..."],"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/go.yaml.in/yaml/v3@v3.0.5"],"schemaVersion":1,"subject":"pkg:golang/go.yaml.in/yaml/v3@v3.0.5","symbols":["Node"],"verifierAdapter":"golang@1"}

module sample

go 1.22

require go.yaml.in/yaml/v3 v3.0.5

go.yaml.in/yaml/v3 v3.0.5 h1:N6y/pJk8buWs9NY5ERU2HSMfm+IuD/OtfdAnq6kESPw=
go.yaml.in/yaml/v3 v3.0.5/go.mod h1:HVTZu1O7/Vkt2N+BFy8Zza+lnLsABggaTM2ZpNIGuKg=

{
  "schemaVersion": 1,
  "goal": "verify pkg:golang/go.yaml.in/yaml/v3@v3.0.5",
  "kind": "HOW",
  "packages": [
    "pkg:golang/go.yaml.in/yaml/v3@v3.0.5"
  ],
  "symbols": [
    "Node"
  ]
}