cloud.google.com/go/auth v0.24.1: Style

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 cloud.google.com/go/auth.Style in pkg:golang/cloud.google.com/go/auth@v0.24.1
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/cloud.google.com/go/auth@v0.24.1
Demonstrate these symbols/APIs:
  - cloud.google.com/go/auth.Style

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:c8c65f9921291a70b6684c8936f6e0467f62990159984794ef323a736f499547","contract":["auth.Style is an integer type representing OAuth 2.0 client authentication styles","auth.Style zero-value is auth.StyleUnknown","auth.Style constants StyleUnknown, StyleInParams, and StyleInHeader are distinct","auth.Options3LO uses auth.Style in its AuthStyle field and defaults to StyleUnknown","auth.New3LOTokenProvider accepts auth.StyleInParams and auth.StyleInHeader, but rejects auth.StyleUnknown"],"goal":"verify cloud.google.com/go/auth.Style in pkg:golang/cloud.google.com/go/auth@v0.24.1","kind":"HOW","packages":["pkg:golang/cloud.google.com/go/auth@v0.24.1"],"schemaVersion":1,"symbols":["cloud.google.com/go/auth.Style"]},"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/cloud.google.com/go/auth@v0.24.1"],"schemaVersion":1,"subject":"pkg:golang/cloud.google.com/go/auth@v0.24.1","symbols":["cloud.google.com/go/auth.Style"],"verifierAdapter":"golang@1"}

module sample

go 1.26.6

require cloud.google.com/go/auth v0.24.1

require (
	cloud.google.com/go/compute/metadata v0.9.0 // indirect
	github.com/googleapis/gax-go/v2 v2.26.2 // indirect
	golang.org/x/sys v0.47.0 // indirect
)

cloud.google.com/go/auth v0.24.1 h1:NTmd2iJb4DsGIav0KiqFMYI88nMshA2wnFMBatRmoCs=
cloud.google.com/go/auth v0.24.1/go.mod h1:1dmBXa9xfBvBr39ZnDUDkaaA91ccq9CcqENDgJA4d7c=
cloud.google.com/go/compute/metadata v0.9.0 h1:pDUj4QMoPejqq20dK0Pg2N4yG9zIkYGdBtwLoEkH9Zs=
cloud.google.com/go/compute/metadata v0.9.0/go.mod h1:E0bWwX5wTnLPedCKqk3pJmVgCBSM6qQI1yTBdEb3C10=
github.com/cespare/xxhash/v2 v2.3.0 h1:UL815xU9SqsFlibzuggzjXhog7bL6oX9BbNZnL2UFvs=
github.com/cespare/xxhash/v2 v2.3.0/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
github.com/felixge/httpsnoop v1.0.4 h1:NFTV2Zj1bL4mc9sqWACXbQFVBBg2W3GPvqp8/ESS2Wg=
github.com/felixge/httpsnoop v1.0.4/go.mod h1:m8KPJKqk1gH5J9DgRY2ASl2lWCfGKXixSwevea8zH2U=
github.com/go-logr/logr v1.4.4 h1:tG4xh9yMsRCAiodLVTxyrkzSZ9+o0L1Kg/+cPVcbP/8=
github.com/go-logr/logr v1.4.4/go.mod h1:9T104GzyrTigFIr8wt5mBrctHMim0Nb2HLGrmQ40KvY=
github.com/go-logr/stdr v1.2.2 h1:hSWxHoqTgW2S2qGc0LTAI563KZ5YKYRhT3MFKZMbjag=
github.com/go-logr/stdr v1.2.2/go.mod h1:mMo/vtBO5dYbehREoey6XUKy/eSumjCCveDpRre4VKE=
github.com/google/go-cmp v0.7.0 h1:wk8382ETsv4JYUZwIsn6YpYiWiBsYLSJiTsyBybVuN8=
github.com/google/go-cmp v0.7.0/go.mod h1:pXiqmnSA92OHEEa9HXL2W4E7lf9JzCmGVUdgjX3N/iU=
github.com/google/s2a-go v0.1.9 h1:LGD7gtMgezd8a/Xak7mEWL0PjoTQFvpRudN895yqKW0=
github.com/google/s2a-go v0.1.9/go.mod h1:YA0Ei2ZQL3acow2O62kdp9UlnvMmU7kA6Eutn0dXayM=
github.com/googleapis/enterprise-certificate-proxy v0.3.17 h1:73NfMHdiqo9JFU9+7a5ExpVa10/R29pXfZIaW559nrg=
github.com/googleapis/enterprise-certificate-proxy v0.3.17/go.mod h1:rSEsBUemEBZEexP2y6jPp16LUmUbjmSbcPMQizR0o4k=
github.com/googleapis/gax-go/v2 v2.26.2 h1:ydkmNXxj7bEmmeK5AihkKnWxyOyBR9TDebvp5L5izk8=
github.com/googleapis/gax-go/v2 v2.26.2/go.mod h1:sMKqnMesnKH+3wiRJROcttA+cJoZoGbZl1vDQ8XYtGk=
go.opentelemetry.io/auto/sdk v1.2.1 h1:jXsnJ4Lmnqd11kwkBV2LgLoFMZKizbCi5fNZ/ipaZ64=
go.opentelemetry.io/auto/sdk v1.2.1/go.mod h1:KRTj+aOaElaLi+wW1kO/DZRXwkF4C5xPbEe3ZiIhN7Y=
go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.67.0 h1:OyrsyzuttWTSur2qN/Lm0m2a8yqyIjUVBZcxFPuXq2o=
go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.67.0/go.mod h1:C2NGBr+kAB4bk3xtMXfZ94gqFDtg/GkI7e9zqGh5Beg=
go.opentelemetry.io/otel v1.45.0 h1:pdrWmLHofpubmArBv1LgFSv1Z0Ie/ppdZzu+kUN5EeU=
go.opentelemetry.io/otel v1.45.0/go.mod h1:XZxIqPapzEYnhNSScF5DIqXhm/rYi0FzCe2XddAwZfQ=
go.opentelemetry.io/otel/metric v1.45.0 h1:7Eg1uH7CJ5cXv9is6tnBe1FI6rj1nwUdbFypRm3br/M=
go.opentelemetry.io/otel/metric v1.45.0/go.mod h1:HAPbm1nd3p1PmFH7v2dR+6BjXxw+Lq4a2+pndMAm08s=
go.opentelemetry.io/otel/trace v1.45.0 h1:l/mP6Uv7oNO7/TblbhpbgMidxhq1uO/rPsikOyVhxag=
go.opentelemetry.io/otel/trace v1.45.0/go.mod h1:qoJJA2xNMnxRrdISU/kLtfUH2wNeQbiv+jhs/CxI8bc=
golang.org/x/crypto v0.55.0 h1:+KWHjbgOaAQ66dh/YlkZKHlz9ZUlq61AFirAR9ntP8M=
golang.org/x/crypto v0.55.0/go.mod h1:uq0V9dE/fzQuJtbnL+2EhWOE63vo164FY8xqEnV9xis=
golang.org/x/net v0.58.0 h1:ynWG7rqYi4ccpTEuPZ2QGWHktVEM9DMCj9yzDE0Q7To=
golang.org/x/net v0.58.0/go.mod h1:YwCddHnFlT7eLQqVprV19OnhLGtc5xOKgE0RyqgfWAU=
golang.org/x/sys v0.47.0 h1:o7XGOvZQCADBQQ4Y7VNq2dRWQR7JmOUW8Kxx4ZsNgWs=
golang.org/x/sys v0.47.0/go.mod h1:4GL1E5IUh+htKOUEOaiffhrAeqysfVGipDYzABqnCmw=
golang.org/x/text v0.41.0 h1:vz/seA0lnX87Othu2f/0L24RcgrXD9/YFTSuGjj3rH8=
golang.org/x/text v0.41.0/go.mod h1:jvf1O8ajNzZqhSrQBPbutR/EB83Cc0CFrezNQIwbb5M=
google.golang.org/api v0.288.0 h1:glhO/J88obKP5I269W3hB73dvBKrjU56ZfmNlNXpgTU=
google.golang.org/api v0.288.0/go.mod h1:lM2kYRzYUCBY91P9h6VF1PYmvhxii3O5hji37qRvIcY=
google.golang.org/genproto v0.0.0-20260715232425-e75dac1f907d h1:C9v1o0/4quuhOAfmRXA2j+we0PqZIp8traLdeogF3Ms=
google.golang.org/genproto/googleapis/rpc v0.0.0-20260715232425-e75dac1f907d h1:Jkpk39hlTZOIp3RbfvNX9R8Hv+Sw0X89nlU/xFOErsc=
google.golang.org/genproto/googleapis/rpc v0.0.0-20260715232425-e75dac1f907d/go.mod h1:4Hqkh8ycfw05ld/3BWL7rJOSfebL2Q+DVDeRgYgxUU8=
google.golang.org/grpc v1.83.2 h1:EManeRomTObA0BU7I8vXgg/78uE5MJ9M8B39EX2WscU=
google.golang.org/grpc v1.83.2/go.mod h1:YPI1hK3kDked6iHvgX3tR0y+nX/qpMFKhPgFsokw1S8=
google.golang.org/protobuf v1.36.11 h1:fV6ZwhNocDyBLK0dj+fg8ektcVegBBuEolpbTQyBNVE=
google.golang.org/protobuf v1.36.11/go.mod h1:HTf+CrKn2C3g5S8VImy6tdcUvCska2kB7j23XfzDpco=

package sample

import (
	"errors"

	"cloud.google.com/go/auth"
)

// ValidateAuthStyle checks if the provided Style is supported and configured.
// It returns an error if the style is StyleUnknown or an unrecognized value.
func ValidateAuthStyle(s auth.Style) error {
	switch s {
	case auth.StyleInParams, auth.StyleInHeader:
		return nil
	case auth.StyleUnknown:
		return errors.New("auth: auth style must be provided")
	default:
		return errors.New("auth: unknown auth style")
	}
}

// New3LOOptions creates an Options3LO struct configured with the given auth.Style.
func New3LOOptions(clientID, clientSecret, authURL, tokenURL, refreshToken string, style auth.Style) *auth.Options3LO {
	return &auth.Options3LO{
		ClientID:     clientID,
		ClientSecret: clientSecret,
		AuthURL:      authURL,
		TokenURL:     tokenURL,
		AuthStyle:    style,
		RefreshToken: refreshToken,
	}
}

// CreateTokenProvider creates a TokenProvider from the given options.
func CreateTokenProvider(opts *auth.Options3LO) (auth.TokenProvider, error) {
	return auth.New3LOTokenProvider(opts)
}

{
  "schemaVersion": 1,
  "goal": "verify cloud.google.com/go/auth.Style in pkg:golang/cloud.google.com/go/auth@v0.24.1",
  "kind": "HOW",
  "packages": [
    "pkg:golang/cloud.google.com/go/auth@v0.24.1"
  ],
  "symbols": [
    "cloud.google.com/go/auth.Style"
  ]
}

package main

import (
	"fmt"
	"os"
	"strings"

	"cloud.google.com/go/auth"
	"sample"
)

func main() {
	if err := runContractTests(); err != nil {
		fmt.Fprintf(os.Stderr, "Contract test failed: %v\n", err)
		os.Exit(1)
	}
	fmt.Println("PASS: cloud.google.com/go/auth.Style contract verified")
}

func runContractTests() error {
	// Assertion 1: auth.Style is an integer type representing OAuth 2.0 client authentication styles
	var s0, s1, s2 auth.Style = auth.Style(0), auth.Style(1), auth.Style(2)
	if s0 != auth.StyleUnknown {
		return fmt.Errorf("expected auth.Style(0) == StyleUnknown, got %v", s0)
	}
	if s1 != auth.StyleInParams {
		return fmt.Errorf("expected auth.Style(1) == StyleInParams, got %v", s1)
	}
	if s2 != auth.StyleInHeader {
		return fmt.Errorf("expected auth.Style(2) == StyleInHeader, got %v", s2)
	}

	// Assertion 2: auth.Style zero-value is auth.StyleUnknown
	var defaultStyle auth.Style
	if defaultStyle != auth.StyleUnknown {
		return fmt.Errorf("expected zero-valued auth.Style to be StyleUnknown, got %v", defaultStyle)
	}

	// Assertion 3: auth.Style constants StyleUnknown, StyleInParams, and StyleInHeader are distinct
	if auth.StyleUnknown == auth.StyleInParams {
		return fmt.Errorf("auth.StyleUnknown equals auth.StyleInParams")
	}
	if auth.StyleUnknown == auth.StyleInHeader {
		return fmt.Errorf("auth.StyleUnknown equals auth.StyleInHeader")
	}
	if auth.StyleInParams == auth.StyleInHeader {
		return fmt.Errorf("auth.StyleInParams equals auth.StyleInHeader")
	}

	// Assertion 4: auth.Options3LO uses auth.Style in its AuthStyle field and defaults to StyleUnknown
	defaultOpts := &auth.Options3LO{}
	if defaultOpts.AuthStyle != auth.StyleUnknown {
		return fmt.Errorf("expected default Options3LO.AuthStyle to be StyleUnknown, got %v", defaultOpts.AuthStyle)
	}
	if err := sample.ValidateAuthStyle(defaultOpts.AuthStyle); err == nil {
		return fmt.Errorf("expected ValidateAuthStyle to reject default StyleUnknown")
	}

	// Assertion 5: auth.New3LOTokenProvider accepts auth.StyleInParams and auth.StyleInHeader, but rejects auth.StyleUnknown
	optsUnknown := sample.New3LOOptions("client-id", "client-secret", "http://localhost/auth", "http://localhost/token", "refresh-token", auth.StyleUnknown)
	tpUnknown, err := sample.CreateTokenProvider(optsUnknown)
	if err == nil {
		return fmt.Errorf("expected New3LOTokenProvider to fail with StyleUnknown, got provider: %v", tpUnknown)
	}
	if !strings.Contains(err.Error(), "auth style must be provided") {
		return fmt.Errorf("expected 'auth style must be provided' error, got: %v", err)
	}

	optsParams := sample.New3LOOptions("client-id", "client-secret", "http://localhost/auth", "http://localhost/token", "refresh-token", auth.StyleInParams)
	if err := sample.ValidateAuthStyle(optsParams.AuthStyle); err != nil {
		return fmt.Errorf("ValidateAuthStyle rejected StyleInParams: %w", err)
	}
	tpParams, err := sample.CreateTokenProvider(optsParams)
	if err != nil {
		return fmt.Errorf("failed to create TokenProvider with StyleInParams: %w", err)
	}
	if tpParams == nil {
		return fmt.Errorf("expected non-nil TokenProvider with StyleInParams")
	}

	optsHeader := sample.New3LOOptions("client-id", "client-secret", "http://localhost/auth", "http://localhost/token", "refresh-token", auth.StyleInHeader)
	if err := sample.ValidateAuthStyle(optsHeader.AuthStyle); err != nil {
		return fmt.Errorf("ValidateAuthStyle rejected StyleInHeader: %w", err)
	}
	tpHeader, err := sample.CreateTokenProvider(optsHeader)
	if err != nil {
		return fmt.Errorf("failed to create TokenProvider with StyleInHeader: %w", err)
	}
	if tpHeader == nil {
		return fmt.Errorf("expected non-nil TokenProvider with StyleInHeader")
	}

	return nil
}