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

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.CredentialsPropertyFunc 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.CredentialsPropertyFunc

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:sha256:898506c3030dfe4ff173187f002240fdb74847bdce4b4bc5c64f0b6931ed5d9d","contract":["CredentialsPropertyFunc implements CredentialsPropertyProvider interface","CredentialsPropertyFunc.GetProperty returns property string and nil error on success","CredentialsPropertyFunc.GetProperty propagates errors returned by the underlying function","CredentialsPropertyFunc.GetProperty forwards context to the underlying function","CredentialsPropertyFunc configures Credentials ProjectIDProvider to resolve project ID","CredentialsPropertyFunc configures Credentials UniverseDomainProvider to resolve universe domain"],"goal":"verify cloud.google.com/go/auth.CredentialsPropertyFunc 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.CredentialsPropertyFunc"]},"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.CredentialsPropertyFunc"],"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"

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

func main() {
	fn := auth.CredentialsPropertyFunc(func(ctx context.Context) (string, error) {
		return "sample-project", nil
	})

	val, err := fn.GetProperty(context.Background())
	if err != nil {
		fmt.Printf("Error: %v\n", err)
		return
	}
	fmt.Printf("Property: %s\n", val)
}

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

package main

import (
	"context"
	"errors"
	"fmt"
	"os"

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

type testContextKey struct{}

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

func runTests() error {
	// 1. CredentialsPropertyFunc implements CredentialsPropertyProvider interface
	{
		var provider auth.CredentialsPropertyProvider = auth.CredentialsPropertyFunc(func(ctx context.Context) (string, error) {
			return "prop-value", nil
		})
		val, err := provider.GetProperty(context.Background())
		if err != nil {
			return fmt.Errorf("assertion 1 failed: %w", err)
		}
		if val != "prop-value" {
			return fmt.Errorf("assertion 1 failed: expected %q, got %q", "prop-value", val)
		}
	}

	// 2. CredentialsPropertyFunc.GetProperty returns property string and nil error on success
	{
		fn := auth.CredentialsPropertyFunc(func(ctx context.Context) (string, error) {
			return "resolved-value", nil
		})
		val, err := fn.GetProperty(context.Background())
		if err != nil {
			return fmt.Errorf("assertion 2 failed: %w", err)
		}
		if val != "resolved-value" {
			return fmt.Errorf("assertion 2 failed: expected %q, got %q", "resolved-value", val)
		}
	}

	// 3. CredentialsPropertyFunc.GetProperty propagates errors returned by the underlying function
	{
		expectedErr := errors.New("underlying error")
		fn := auth.CredentialsPropertyFunc(func(ctx context.Context) (string, error) {
			return "", expectedErr
		})
		val, err := fn.GetProperty(context.Background())
		if err == nil {
			return fmt.Errorf("assertion 3 failed: expected error, got nil")
		}
		if !errors.Is(err, expectedErr) {
			return fmt.Errorf("assertion 3 failed: expected error %v, got %v", expectedErr, err)
		}
		if val != "" {
			return fmt.Errorf("assertion 3 failed: expected empty string on error, got %q", val)
		}
	}

	// 4. CredentialsPropertyFunc.GetProperty forwards context to the underlying function
	{
		ctx := context.WithValue(context.Background(), testContextKey{}, "test-value")
		fn := auth.CredentialsPropertyFunc(func(c context.Context) (string, error) {
			val, ok := c.Value(testContextKey{}).(string)
			if !ok {
				return "", errors.New("context key not found")
			}
			return val, nil
		})
		val, err := fn.GetProperty(ctx)
		if err != nil {
			return fmt.Errorf("assertion 4 failed: %w", err)
		}
		if val != "test-value" {
			return fmt.Errorf("assertion 4 failed: expected %q, got %q", "test-value", val)
		}
	}

	// 5. CredentialsPropertyFunc configures Credentials ProjectIDProvider to resolve project ID
	{
		creds := auth.NewCredentials(&auth.CredentialsOptions{
			ProjectIDProvider: auth.CredentialsPropertyFunc(func(ctx context.Context) (string, error) {
				return "sample-project-id", nil
			}),
		})
		projectID, err := creds.ProjectID(context.Background())
		if err != nil {
			return fmt.Errorf("assertion 5 failed: %w", err)
		}
		if projectID != "sample-project-id" {
			return fmt.Errorf("assertion 5 failed: expected %q, got %q", "sample-project-id", projectID)
		}
	}

	// 6. CredentialsPropertyFunc configures Credentials UniverseDomainProvider to resolve universe domain
	{
		creds := auth.NewCredentials(&auth.CredentialsOptions{
			UniverseDomainProvider: auth.CredentialsPropertyFunc(func(ctx context.Context) (string, error) {
				return "example.com", nil
			}),
		})
		domain, err := creds.UniverseDomain(context.Background())
		if err != nil {
			return fmt.Errorf("assertion 6 failed: %w", err)
		}
		if domain != "example.com" {
			return fmt.Errorf("assertion 6 failed: expected %q, got %q", "example.com", domain)
		}
	}

	return nil
}