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

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.TokenProvider 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.TokenProvider

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:a430ce57eda3db6dc4d9e4bb3bdd700ff213cf2298dd2bb462a53a30c6c7f96f","contract":["Custom type implementing TokenProvider interface returns an auth.Token with valid Value, Type, and Expiry","TokenProvider receives context and respects cancellation during token resolution","TokenProvider returns custom error when token resolution fails and caller receives it","Credentials wraps and embeds TokenProvider delegating Token resolution to the underlying provider","NewCachedTokenProvider accepts a custom TokenProvider implementation and returns cached tokens"],"goal":"verify cloud.google.com/go/auth.TokenProvider 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.TokenProvider"]},"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.TokenProvider"],"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 main

import (
	"context"
	"fmt"
	"time"

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

type staticTokenProvider struct {
	token *auth.Token
}

func (p *staticTokenProvider) Token(ctx context.Context) (*auth.Token, error) {
	return p.token, nil
}

func main() {
	ctx := context.Background()

	var provider auth.TokenProvider = &staticTokenProvider{
		token: &auth.Token{
			Value:  "sample-token-12345",
			Type:   "Bearer",
			Expiry: time.Now().Add(1 * time.Hour),
		},
	}

	tok, err := provider.Token(ctx)
	if err != nil {
		panic(err)
	}

	fmt.Printf("Token value: %s, type: %s, valid: %t\n", tok.Value, tok.Type, tok.IsValid())
}

{
  "schemaVersion": 1,
  "goal": "verify cloud.google.com/go/auth.TokenProvider 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.TokenProvider"
  ]
}

package main

import (
	"context"
	"errors"
	"fmt"
	"os"
	"sync"
	"time"

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

type customStaticProvider struct {
	token *auth.Token
}

func (p *customStaticProvider) Token(ctx context.Context) (*auth.Token, error) {
	return p.token, nil
}

type contextAwareProvider struct{}

func (p *contextAwareProvider) Token(ctx context.Context) (*auth.Token, error) {
	if err := ctx.Err(); err != nil {
		return nil, err
	}
	return &auth.Token{
		Value:  "ctx-token-value",
		Type:   "Bearer",
		Expiry: time.Now().Add(1 * time.Hour),
	}, nil
}

type customErrorProvider struct {
	err error
}

func (p *customErrorProvider) Token(ctx context.Context) (*auth.Token, error) {
	return nil, p.err
}

type countingProvider struct {
	mu    sync.Mutex
	calls int
}

func (p *countingProvider) Token(ctx context.Context) (*auth.Token, error) {
	p.mu.Lock()
	defer p.mu.Unlock()
	p.calls++
	return &auth.Token{
		Value:  fmt.Sprintf("token-%d", p.calls),
		Type:   "Bearer",
		Expiry: time.Now().Add(1 * time.Hour),
	}, nil
}

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

func runTests() error {
	ctx := context.Background()

	// Assertion 1: Custom type implementing TokenProvider interface returns an auth.Token with valid Value, Type, and Expiry
	{
		validTok := &auth.Token{
			Value:  "static-token-abc",
			Type:   "Bearer",
			Expiry: time.Now().Add(1 * time.Hour),
		}
		var tp auth.TokenProvider = &customStaticProvider{token: validTok}
		tok, err := tp.Token(ctx)
		if err != nil {
			return fmt.Errorf("assertion 1 failed: unexpected error: %w", err)
		}
		if tok == nil || tok.Value != "static-token-abc" || tok.Type != "Bearer" {
			return fmt.Errorf("assertion 1 failed: invalid token returned: %+v", tok)
		}
		if !tok.IsValid() {
			return fmt.Errorf("assertion 1 failed: expected token to be valid")
		}
	}

	// Assertion 2: TokenProvider receives context and respects cancellation during token resolution
	{
		var tp auth.TokenProvider = &contextAwareProvider{}
		canceledCtx, cancel := context.WithCancel(ctx)
		cancel()

		_, err := tp.Token(canceledCtx)
		if !errors.Is(err, context.Canceled) {
			return fmt.Errorf("assertion 2 failed: expected context.Canceled error, got: %v", err)
		}

		tok, err := tp.Token(ctx)
		if err != nil {
			return fmt.Errorf("assertion 2 failed: unexpected error with valid context: %w", err)
		}
		if tok == nil || tok.Value != "ctx-token-value" {
			return fmt.Errorf("assertion 2 failed: expected valid token with active context")
		}
	}

	// Assertion 3: TokenProvider returns custom error when token resolution fails and caller receives it
	{
		sentinelErr := errors.New("failed to acquire token from source")
		var tp auth.TokenProvider = &customErrorProvider{err: sentinelErr}

		tok, err := tp.Token(ctx)
		if tok != nil {
			return fmt.Errorf("assertion 3 failed: expected nil token on error, got: %+v", tok)
		}
		if !errors.Is(err, sentinelErr) {
			return fmt.Errorf("assertion 3 failed: expected sentinel error %v, got: %v", sentinelErr, err)
		}
	}

	// Assertion 4: Credentials wraps and embeds TokenProvider delegating Token resolution to the underlying provider
	{
		rawTok := &auth.Token{
			Value:  "creds-delegated-token",
			Type:   "Bearer",
			Expiry: time.Now().Add(2 * time.Hour),
		}
		baseProv := &customStaticProvider{token: rawTok}
		creds := auth.NewCredentials(&auth.CredentialsOptions{
			TokenProvider: baseProv,
		})

		var tp auth.TokenProvider = creds
		tok, err := tp.Token(ctx)
		if err != nil {
			return fmt.Errorf("assertion 4 failed: unexpected error: %w", err)
		}
		if tok == nil || tok.Value != "creds-delegated-token" {
			return fmt.Errorf("assertion 4 failed: unexpected token: %+v", tok)
		}
	}

	// Assertion 5: NewCachedTokenProvider accepts a custom TokenProvider implementation and returns cached tokens
	{
		counter := &countingProvider{}
		var rawTP auth.TokenProvider = counter
		cachedTP := auth.NewCachedTokenProvider(rawTP, nil)

		var tp auth.TokenProvider = cachedTP
		tok1, err := tp.Token(ctx)
		if err != nil {
			return fmt.Errorf("assertion 5 failed on first call: %w", err)
		}
		tok2, err := tp.Token(ctx)
		if err != nil {
			return fmt.Errorf("assertion 5 failed on second call: %w", err)
		}
		if tok1.Value != tok2.Value {
			return fmt.Errorf("assertion 5 failed: expected cached token values to match, got %q vs %q", tok1.Value, tok2.Value)
		}
		if counter.calls != 1 {
			return fmt.Errorf("assertion 5 failed: expected 1 underlying call, got %d", counter.calls)
		}
	}

	return nil
}