cloud.google.com/go/auth v0.18.2: CachedTokenProviderOptions

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.CachedTokenProviderOptions in pkg:golang/cloud.google.com/go/auth@v0.18.2
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/cloud.google.com/go/auth@v0.18.2
Demonstrate these symbols/APIs:
  - cloud.google.com/go/auth.CachedTokenProviderOptions

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:sha256:08d93e9fe59356b8b11d9f8dfbdb570eb97f1abb647e07f70e97c994c0054b1c","contract":["CachedTokenProviderOptions enables caching of valid tokens across multiple calls to avoid duplicate provider invocations","CachedTokenProviderOptions with DisableAutoRefresh returns the cached token even when the token has expired","CachedTokenProviderOptions with DisableAsyncRefresh ensures blocking synchronous token refresh when tokens expire","CachedTokenProviderOptions with ExpireEarly triggers proactive refresh for tokens within the expiration window"],"goal":"verify cloud.google.com/go/auth.CachedTokenProviderOptions in pkg:golang/cloud.google.com/go/auth@v0.18.2","kind":"HOW","packages":["pkg:golang/cloud.google.com/go/auth@v0.18.2"],"schemaVersion":1,"symbols":["cloud.google.com/go/auth.CachedTokenProviderOptions"]},"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@v0.18.2"],"schemaVersion":1,"subject":"pkg:golang/cloud.google.com/go/auth@v0.18.2","symbols":["cloud.google.com/go/auth.CachedTokenProviderOptions"],"verifierAdapter":"golang@1"}

module sample

go 1.26.6

require cloud.google.com/go/auth v0.18.2

require (
	cloud.google.com/go/compute/metadata v0.9.0 // indirect
	github.com/googleapis/gax-go/v2 v2.17.0 // indirect
	golang.org/x/sys v0.40.0 // indirect
)

cloud.google.com/go/auth v0.18.2 h1:+Nbt5Ev0xEqxlNjd6c+yYUeosQ5TtEUaNcN/3FozlaM=
cloud.google.com/go/auth v0.18.2/go.mod h1:xD+oY7gcahcu7G2SG2DsBerfFxgPAJz17zz2joOFF3M=
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 v1.4.3 h1:CjnDlHq8ikf6E492q6eKboGOC0T8CDaOvkHCIg8idEI=
github.com/go-logr/logr v1.4.3/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 v0.3.11 h1:vAe81Msw+8tKUxi2Dqh/NZMz7475yUvmRIkXr4oN2ao=
github.com/googleapis/enterprise-certificate-proxy v0.3.11/go.mod h1:RFV7MUdlb7AgEq2v7FmMCfeSMCllAzWxFgRdusoGks8=
github.com/googleapis/gax-go/v2 v2.17.0 h1:RksgfBpxqff0EZkDWYuz9q/uWsTVz+kf43LsZ1J6SMc=
github.com/googleapis/gax-go/v2 v2.17.0/go.mod h1:mzaqghpQp4JDh3HvADwrat+6M3MOIDp5YKHhb9PAgDY=
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 v0.61.0 h1:F7Jx+6hwnZ41NSFTO5q4LYDtJRXBf2PD0rNBkeB/lus=
go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.61.0/go.mod h1:UHB22Z8QsdRDrnAtX4PntOl36ajSxcdUMt1sF7Y6E7Q=
go.opentelemetry.io/otel v1.39.0 h1:8yPrr/S0ND9QEfTfdP9V+SiwT4E0G7Y5MO7p85nis48=
go.opentelemetry.io/otel v1.39.0/go.mod h1:kLlFTywNWrFyEdH0oj2xK0bFYZtHRYUdv1NklR/tgc8=
go.opentelemetry.io/otel/metric v1.39.0 h1:d1UzonvEZriVfpNKEVmHXbdf909uGTOQjA0HF0Ls5Q0=
go.opentelemetry.io/otel/metric v1.39.0/go.mod h1:jrZSWL33sD7bBxg1xjrqyDjnuzTUB0x1nBERXd7Ftcs=
go.opentelemetry.io/otel/trace v1.39.0 h1:2d2vfpEDmCJ5zVYz7ijaJdOF59xLomrvj7bjt6/qCJI=
go.opentelemetry.io/otel/trace v1.39.0/go.mod h1:88w4/PnZSazkGzz/w84VHpQafiU4EtqqlVdxWy+rNOA=
golang.org/x/crypto v0.47.0 h1:V6e3FRj+n4dbpw86FJ8Fv7XVOql7TEwpHapKoMJ/GO8=
golang.org/x/crypto v0.47.0/go.mod h1:ff3Y9VzzKbwSSEzWqJsJVBnWmRwRSHt/6Op5n9bQc4A=
golang.org/x/net v0.49.0 h1:eeHFmOGUTtaaPSGNmjBKpbng9MulQsJURQUAfUwY++o=
golang.org/x/net v0.49.0/go.mod h1:/ysNB2EvaqvesRkuLAyjI1ycPZlQHM3q01F02UY/MV8=
golang.org/x/sys v0.40.0 h1:DBZZqJ2Rkml6QMQsZywtnjnnGvHza6BTfYFWY9kjEWQ=
golang.org/x/sys v0.40.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
golang.org/x/text v0.33.0 h1:B3njUFyqtHDUI5jMn1YIr5B0IE2U0qck04r6d4KPAxE=
golang.org/x/text v0.33.0/go.mod h1:LuMebE6+rBincTi9+xWTY8TztLzKHc/9C1uBCG27+q8=
google.golang.org/genproto v0.0.0-20260128011058-8636f8732409 h1:VQZ/yAbAtjkHgH80teYd2em3xtIkkHd7ZhqfH2N9CsM=
google.golang.org/genproto/googleapis/rpc v0.0.0-20260128011058-8636f8732409 h1:H86B94AW+VfJWDqFeEbBPhEtHzJwJfTbgE2lZa54ZAQ=
google.golang.org/genproto/googleapis/rpc v0.0.0-20260128011058-8636f8732409/go.mod h1:j9x/tPzZkyxcgEFkiKEEGxfvyumM01BEtsW8xzOahRQ=
google.golang.org/grpc v1.78.0 h1:K1XZG/yGDJnzMdd/uZHAkVqJE+xIDOcmdSFZkBUicNc=
google.golang.org/grpc v1.78.0/go.mod h1:I47qjTo4OKbMkjA/aOOwxDIiPSBofUtQUI5EfpWvW7U=
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"
)

// staticTokenProvider implements auth.TokenProvider returning a fixed token.
type staticTokenProvider struct {
	token *auth.Token
}

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

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

	baseProvider := &staticTokenProvider{
		token: &auth.Token{
			Value:  "sample-access-token-xyz",
			Type:   "Bearer",
			Expiry: time.Now().Add(1 * time.Hour),
		},
	}

	// Configure caching behavior using CachedTokenProviderOptions
	opts := &auth.CachedTokenProviderOptions{
		DisableAutoRefresh:  false,
		ExpireEarly:         5 * time.Minute,
		DisableAsyncRefresh: true,
	}

	cachedProvider := auth.NewCachedTokenProvider(baseProvider, opts)

	token, err := cachedProvider.Token(ctx)
	if err != nil {
		fmt.Printf("failed to retrieve cached token: %v\n", err)
		return
	}

	fmt.Printf("Retrieved token type: %s, valid: %t\n", token.Type, token.IsValid())
}

{
  "schemaVersion": 1,
  "goal": "verify cloud.google.com/go/auth.CachedTokenProviderOptions in pkg:golang/cloud.google.com/go/auth@v0.18.2",
  "kind": "HOW",
  "packages": [
    "pkg:golang/cloud.google.com/go/auth@v0.18.2"
  ],
  "symbols": [
    "cloud.google.com/go/auth.CachedTokenProviderOptions"
  ]
}

package main

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

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

type sequenceTokenProvider struct {
	mu     sync.Mutex
	calls  int
	tokens []*auth.Token
	notify chan struct{}
}

func (s *sequenceTokenProvider) Token(ctx context.Context) (*auth.Token, error) {
	s.mu.Lock()
	defer s.mu.Unlock()
	idx := s.calls
	s.calls++
	var tok *auth.Token
	if idx < len(s.tokens) {
		tok = s.tokens[idx]
	} else {
		tok = s.tokens[len(s.tokens)-1]
	}
	if s.notify != nil {
		select {
		case s.notify <- struct{}{}:
		default:
		}
	}
	return tok, nil
}

func (s *sequenceTokenProvider) callCount() int {
	s.mu.Lock()
	defer s.mu.Unlock()
	return s.calls
}

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

	// Assertion 1: CachedTokenProviderOptions enables caching of valid tokens across multiple calls to avoid duplicate provider invocations
	{
		validToken := &auth.Token{
			Value:  "valid-token-123",
			Type:   "Bearer",
			Expiry: time.Now().Add(1 * time.Hour),
		}
		mock := &sequenceTokenProvider{
			tokens: []*auth.Token{validToken},
		}

		opts := &auth.CachedTokenProviderOptions{}
		cached := auth.NewCachedTokenProvider(mock, opts)

		for i := 0; i < 3; i++ {
			tok, err := cached.Token(ctx)
			if err != nil {
				fmt.Fprintf(os.Stderr, "Assertion 1 failed: unexpected error on call %d: %v\n", i+1, err)
				os.Exit(1)
			}
			if tok.Value != "valid-token-123" {
				fmt.Fprintf(os.Stderr, "Assertion 1 failed: expected token %q, got %q\n", "valid-token-123", tok.Value)
				os.Exit(1)
			}
		}

		if mock.callCount() != 1 {
			fmt.Fprintf(os.Stderr, "Assertion 1 failed: expected 1 underlying provider call, got %d\n", mock.callCount())
			os.Exit(1)
		}
	}

	// Assertion 2: CachedTokenProviderOptions with DisableAutoRefresh returns the cached token even when the token has expired
	{
		expiredToken := &auth.Token{
			Value:  "expired-token-val",
			Type:   "Bearer",
			Expiry: time.Now().Add(-10 * time.Minute),
		}
		mock := &sequenceTokenProvider{
			tokens: []*auth.Token{expiredToken},
		}

		opts := &auth.CachedTokenProviderOptions{
			DisableAutoRefresh: true,
		}
		cached := auth.NewCachedTokenProvider(mock, opts)

		tok1, err := cached.Token(ctx)
		if err != nil {
			fmt.Fprintf(os.Stderr, "Assertion 2 failed: initial fetch error: %v\n", err)
			os.Exit(1)
		}
		if tok1.Value != "expired-token-val" {
			fmt.Fprintf(os.Stderr, "Assertion 2 failed: expected initial token %q, got %q\n", "expired-token-val", tok1.Value)
			os.Exit(1)
		}

		tok2, err := cached.Token(ctx)
		if err != nil {
			fmt.Fprintf(os.Stderr, "Assertion 2 failed: second fetch error: %v\n", err)
			os.Exit(1)
		}
		if tok2.Value != "expired-token-val" {
			fmt.Fprintf(os.Stderr, "Assertion 2 failed: expected cached expired token %q, got %q\n", "expired-token-val", tok2.Value)
			os.Exit(1)
		}

		if mock.callCount() != 1 {
			fmt.Fprintf(os.Stderr, "Assertion 2 failed: DisableAutoRefresh should prevent refresh; expected 1 call, got %d\n", mock.callCount())
			os.Exit(1)
		}
	}

	// Assertion 3: CachedTokenProviderOptions with DisableAsyncRefresh ensures blocking synchronous token refresh when tokens expire
	{
		expiredToken := &auth.Token{
			Value:  "expired-initial-token",
			Type:   "Bearer",
			Expiry: time.Now().Add(-5 * time.Minute),
		}
		freshToken := &auth.Token{
			Value:  "fresh-refreshed-token",
			Type:   "Bearer",
			Expiry: time.Now().Add(1 * time.Hour),
		}
		mock := &sequenceTokenProvider{
			tokens: []*auth.Token{expiredToken, freshToken},
		}

		opts := &auth.CachedTokenProviderOptions{
			DisableAutoRefresh:  false,
			DisableAsyncRefresh: true,
		}
		cached := auth.NewCachedTokenProvider(mock, opts)

		tok1, err := cached.Token(ctx)
		if err != nil {
			fmt.Fprintf(os.Stderr, "Assertion 3 failed: initial token retrieval error: %v\n", err)
			os.Exit(1)
		}
		if tok1.Value != "expired-initial-token" {
			fmt.Fprintf(os.Stderr, "Assertion 3 failed: expected initial token %q, got %q\n", "expired-initial-token", tok1.Value)
			os.Exit(1)
		}

		// Second call must block synchronously, detect expiration, and return fresh token
		tok2, err := cached.Token(ctx)
		if err != nil {
			fmt.Fprintf(os.Stderr, "Assertion 3 failed: synchronous refresh error: %v\n", err)
			os.Exit(1)
		}
		if tok2.Value != "fresh-refreshed-token" {
			fmt.Fprintf(os.Stderr, "Assertion 3 failed: expected refreshed token %q, got %q\n", "fresh-refreshed-token", tok2.Value)
			os.Exit(1)
		}

		if mock.callCount() != 2 {
			fmt.Fprintf(os.Stderr, "Assertion 3 failed: expected 2 calls after blocking refresh, got %d\n", mock.callCount())
			os.Exit(1)
		}
	}

	// Assertion 4: CachedTokenProviderOptions with ExpireEarly triggers proactive refresh for tokens within the expiration window
	{
		nearExpiryToken := &auth.Token{
			Value:  "near-expiry-token",
			Type:   "Bearer",
			Expiry: time.Now().Add(10 * time.Second),
		}
		renewedToken := &auth.Token{
			Value:  "proactively-renewed-token",
			Type:   "Bearer",
			Expiry: time.Now().Add(2 * time.Hour),
		}
		notifyCh := make(chan struct{}, 5)
		mock := &sequenceTokenProvider{
			tokens: []*auth.Token{nearExpiryToken, renewedToken},
			notify: notifyCh,
		}

		opts := &auth.CachedTokenProviderOptions{
			ExpireEarly:         30 * time.Second,
			DisableAutoRefresh:  false,
			DisableAsyncRefresh: false,
		}
		cached := auth.NewCachedTokenProvider(mock, opts)

		tok1, err := cached.Token(ctx)
		if err != nil {
			fmt.Fprintf(os.Stderr, "Assertion 4 failed: initial token retrieval error: %v\n", err)
			os.Exit(1)
		}
		if tok1.Value != "near-expiry-token" {
			fmt.Fprintf(os.Stderr, "Assertion 4 failed: expected initial token %q, got %q\n", "near-expiry-token", tok1.Value)
			os.Exit(1)
		}
		<-notifyCh // consume notification from initial fetch

		// Second call: token is within ExpireEarly window (10s left < 30s delta)
		// Should return stale token immediately and trigger async background refresh
		tok2, err := cached.Token(ctx)
		if err != nil {
			fmt.Fprintf(os.Stderr, "Assertion 4 failed: stale token retrieval error: %v\n", err)
			os.Exit(1)
		}
		if tok2.Value != "near-expiry-token" {
			fmt.Fprintf(os.Stderr, "Assertion 4 failed: expected immediate stale token %q, got %q\n", "near-expiry-token", tok2.Value)
			os.Exit(1)
		}

		// Wait for background async refresh to complete
		select {
		case <-notifyCh:
		case <-time.After(2 * time.Second):
			fmt.Fprintf(os.Stderr, "Assertion 4 failed: timed out waiting for proactive async refresh\n")
			os.Exit(1)
		}

		// Third call: should now yield the proactively renewed token
		tok3, err := cached.Token(ctx)
		if err != nil {
			fmt.Fprintf(os.Stderr, "Assertion 4 failed: renewed token retrieval error: %v\n", err)
			os.Exit(1)
		}
		if tok3.Value != "proactively-renewed-token" {
			fmt.Fprintf(os.Stderr, "Assertion 4 failed: expected renewed token %q, got %q\n", "proactively-renewed-token", tok3.Value)
			os.Exit(1)
		}

		if mock.callCount() != 2 {
			fmt.Fprintf(os.Stderr, "Assertion 4 failed: expected 2 calls after proactive refresh, got %d\n", mock.callCount())
			os.Exit(1)
		}
	}

	fmt.Println("PASS: all CachedTokenProviderOptions contract assertions passed")
}