github.com/quic-go/qpack v0.5.1: NewEncoder

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 github.com/quic-go/qpack.NewEncoder in pkg:golang/github.com/quic-go/qpack@v0.5.1
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/github.com/quic-go/qpack@v0.5.1
Demonstrate these symbols/APIs:
  - github.com/quic-go/qpack.NewEncoder
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.

package sample_test

import (
	"bytes"
	"reflect"
	"testing"

	"github.com/quic-go/qpack"
)

func TestNewEncoder(t *testing.T) {
	// 1. qpack.NewEncoder creates an encoder writing QPACK-encoded headers to an io.Writer
	var buf bytes.Buffer
	enc := qpack.NewEncoder(&buf)
	if enc == nil {
		t.Fatalf("expected non-nil Encoder from qpack.NewEncoder")
	}

	// 2. Encoder.WriteField encodes individual HTTP/3 header fields into QPACK wire format
	headers := []qpack.HeaderField{
		{Name: ":method", Value: "POST"},
		{Name: ":path", Value: "/v1/submit"},
		{Name: ":scheme", Value: "https"},
		{Name: ":authority", Value: "example.org"},
		{Name: "content-type", Value: "application/json"},
		{Name: "custom-header", Value: "custom-value"},
	}

	for _, hf := range headers {
		if err := enc.WriteField(hf); err != nil {
			t.Fatalf("failed to write field %v: %v", hf, err)
		}
	}

	// 3. Encoder.Close completes the current header block and resets internal state for subsequent encodings
	if err := enc.Close(); err != nil {
		t.Fatalf("failed to close encoder: %v", err)
	}

	encoded := buf.Bytes()
	if len(encoded) == 0 {
		t.Fatalf("expected non-empty encoded output")
	}

	// 4. qpack.NewDecoder decodes encoded header blocks produced by Encoder to recover original HeaderField values
	dec := qpack.NewDecoder(func(hf qpack.HeaderField) {})
	decoded, err := dec.DecodeFull(encoded)
	if err != nil {
		t.Fatalf("failed to decode header block: %v", err)
	}

	if !reflect.DeepEqual(decoded, headers) {
		t.Fatalf("decoded header mismatch: got %v, want %v", decoded, headers)
	}
}

{"case":{"caseId":"case:sha256:f511e1093be92b073a1ccffae2c9c80aac7baa87fc2820290f24419260a9359f","contract":["qpack.NewEncoder creates an encoder writing QPACK-encoded headers to an io.Writer","Encoder.WriteField encodes individual HTTP/3 header fields into QPACK wire format","Encoder.Close completes the current header block and resets internal state for subsequent encodings","qpack.NewDecoder decodes encoded header blocks produced by Encoder to recover original HeaderField values"],"goal":"verify github.com/quic-go/qpack.NewEncoder in pkg:golang/github.com/quic-go/qpack@v0.5.1","kind":"HOW","packages":["pkg:golang/github.com/quic-go/qpack@v0.5.1"],"schemaVersion":1,"symbols":["github.com/quic-go/qpack.NewEncoder"]},"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/github.com/quic-go/qpack@v0.5.1"],"schemaVersion":1,"subject":"pkg:golang/github.com/quic-go/qpack@v0.5.1","symbols":["github.com/quic-go/qpack.NewEncoder"],"verifierAdapter":"golang@1"}

module sample

go 1.26.6

require github.com/quic-go/qpack v0.5.1

require golang.org/x/net v0.28.0 // indirect

github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
github.com/quic-go/qpack v0.5.1 h1:giqksBPnT/HDtZ6VhtFKgoLOWmlyo9Ei6u9PqzIMbhI=
github.com/quic-go/qpack v0.5.1/go.mod h1:+PC4XFrEskIVkcLzpEkbLqq1uCoxPhQuvK5rH1ZgaEg=
github.com/stretchr/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsTg=
github.com/stretchr/testify v1.9.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
golang.org/x/net v0.28.0 h1:a9JDOJc5GMUJ0+UDqmLT86WiEy7iWyIhz8gz8E4e5hE=
golang.org/x/net v0.28.0/go.mod h1:yqtgsTWOOnlGLG9GFRrK3++bGOUEkNBoHZc8MEDWPNg=
gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

{
  "schemaVersion": 1,
  "goal": "verify github.com/quic-go/qpack.NewEncoder in pkg:golang/github.com/quic-go/qpack@v0.5.1",
  "kind": "HOW",
  "packages": [
    "pkg:golang/github.com/quic-go/qpack@v0.5.1"
  ],
  "symbols": [
    "github.com/quic-go/qpack.NewEncoder"
  ],
  "constraints": {
    "executionContext": "node"
  },
  "runtimeConditions": {
    "ecosystem": "npm",
    "language": "javascript",
    "moduleSystem": "cjs",
    "packageManager": "npm@10.9.8",
    "runtime": "node@22.23.2"
  }
}