golang.org/x/oauth2 v0.36.0: exchange authorization code for access token and create authenticated HTTP client with oauth2.Config

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: exchange authorization code for access token and create authenticated HTTP client with oauth2.Config
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/golang.org/x/oauth2@v0.36.0
Demonstrate these symbols/APIs:
  - oauth2.Config.Client
  - oauth2.Config.Exchange

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:b84c58efc0da1d4dc35866e3d99533d63d1da80501b84e47adfe9b3cba1d43f7","contract":["oauth2.Config.AuthCodeURL generates authorization URL with state, client_id, redirect_uri, and scopes","oauth2.Config.Exchange exchanges authorization code for Token with access_token, token_type, and expiry from token server","oauth2.Config.Exchange returns error when token server responds with HTTP error or invalid grant","oauth2.Config.Client creates an http.Client whose transport adds Authorization Bearer header with the access token","oauth2.Token.Valid returns true for non-empty unexpired token and false for expired token","oauth2.Config.TokenSource returns a TokenSource that automatically refreshes an expired token using refresh_token"],"goal":"exchange authorization code for access token and create authenticated HTTP client with oauth2.Config","kind":"HOW","packages":["pkg:golang/golang.org/x/oauth2@v0.36.0"],"schemaVersion":1,"symbols":["oauth2.Config.Client","oauth2.Config.Exchange"]},"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/golang.org/x/oauth2@v0.36.0"],"schemaVersion":1,"subject":"pkg:golang/golang.org/x/oauth2@v0.36.0","symbols":["oauth2.Config.Client","oauth2.Config.Exchange"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.25.0

require golang.org/x/oauth2 v0.36.0

golang.org/x/oauth2 v0.36.0 h1:peZ/1z27fi9hUOFCAZaHyrpWG5lwe0RJEEEeH0ThlIs=
golang.org/x/oauth2 v0.36.0/go.mod h1:YDBUJMTkDnJS+A4BP4eZBjCqtokkg1hODuPjwiGPO7Q=

package main

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"log"
	"net/http"
	"net/http/httptest"
	"time"

	"golang.org/x/oauth2"
)

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

	// 1. Mock OAuth2 provider server (token endpoint and protected API endpoint)
	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		switch r.URL.Path {
		case "/oauth/token":
			if r.Method != http.MethodPost {
				http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
				return
			}
			_ = r.ParseForm()
			grantType := r.Form.Get("grant_type")
			if grantType == "authorization_code" {
				code := r.Form.Get("code")
				if code == "sample-auth-code" {
					w.Header().Set("Content-Type", "application/json")
					_ = json.NewEncoder(w).Encode(map[string]interface{}{
						"access_token":  "access-token-xyz-123",
						"token_type":    "Bearer",
						"refresh_token": "refresh-token-xyz-456",
						"expires_in":    3600,
					})
					return
				}
				http.Error(w, `{"error":"invalid_grant"}`, http.StatusBadRequest)
				return
			}
			http.Error(w, `{"error":"unsupported_grant_type"}`, http.StatusBadRequest)
			return

		case "/api/userinfo":
			authHeader := r.Header.Get("Authorization")
			if authHeader != "Bearer access-token-xyz-123" {
				http.Error(w, "unauthorized", http.StatusUnauthorized)
				return
			}
			w.Header().Set("Content-Type", "application/json")
			_, _ = io.WriteString(w, `{"sub":"user-42","name":"Demo User"}`)
			return

		default:
			http.NotFound(w, r)
		}
	}))
	defer ts.Close()

	// 2. Configure OAuth2 client
	conf := &oauth2.Config{
		ClientID:     "demo-client-id",
		ClientSecret: "demo-client-secret",
		Scopes:       []string{"profile", "email"},
		RedirectURL:  "https://example.com/oauth/callback",
		Endpoint: oauth2.Endpoint{
			AuthURL:  ts.URL + "/oauth/authorize",
			TokenURL: ts.URL + "/oauth/token",
		},
	}

	// 3. Generate authorization code URL
	authURL := conf.AuthCodeURL("random-state-12345", oauth2.AccessTypeOffline)
	fmt.Printf("Authorization URL: %s\n", authURL)

	// 4. Exchange authorization code for token
	token, err := conf.Exchange(ctx, "sample-auth-code")
	if err != nil {
		log.Fatalf("Failed to exchange code: %v", err)
	}
	fmt.Printf("Obtained Access Token: %s (Type: %s, Expiry: %s)\n",
		token.AccessToken, token.TokenType, token.Expiry.Format(time.RFC3339))

	// 5. Create authenticated HTTP client
	client := conf.Client(ctx, token)
	resp, err := client.Get(ts.URL + "/api/userinfo")
	if err != nil {
		log.Fatalf("Failed to fetch userinfo: %v", err)
	}
	defer resp.Body.Close()

	body, err := io.ReadAll(resp.Body)
	if err != nil {
		log.Fatalf("Failed to read response body: %v", err)
	}
	fmt.Printf("Userinfo Response: %s\n", string(body))
}

{
  "schemaVersion": 1,
  "goal": "exchange authorization code for access token and create authenticated HTTP client with oauth2.Config",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/oauth2@v0.36.0"
  ],
  "symbols": [
    "oauth2.Config.Client",
    "oauth2.Config.Exchange"
  ]
}

package main

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"net/http/httptest"
	"net/url"
	"os"
	"strings"
	"time"

	"golang.org/x/oauth2"
)

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

	// 1. oauth2.Config.AuthCodeURL generates authorization URL with state, client_id, redirect_uri, and scopes
	conf := &oauth2.Config{
		ClientID:     "test-client-id-42",
		ClientSecret: "test-client-secret-99",
		Scopes:       []string{"read", "write"},
		RedirectURL:  "https://example.com/callback",
		Endpoint: oauth2.Endpoint{
			AuthURL:  "https://example.com/oauth/authorize",
			TokenURL: "https://example.com/oauth/token",
		},
	}

	authURLStr := conf.AuthCodeURL("random-state-abc", oauth2.AccessTypeOffline)
	parsedURL, err := url.Parse(authURLStr)
	if err != nil {
		fmt.Fprintf(os.Stderr, "AuthCodeURL produced invalid URL: %v\n", err)
		os.Exit(1)
	}
	query := parsedURL.Query()
	if query.Get("state") != "random-state-abc" {
		fmt.Fprintf(os.Stderr, "AuthCodeURL state mismatch: got %q, want 'random-state-abc'\n", query.Get("state"))
		os.Exit(1)
	}
	if query.Get("client_id") != "test-client-id-42" {
		fmt.Fprintf(os.Stderr, "AuthCodeURL client_id mismatch: got %q, want 'test-client-id-42'\n", query.Get("client_id"))
		os.Exit(1)
	}
	if query.Get("redirect_uri") != "https://example.com/callback" {
		fmt.Fprintf(os.Stderr, "AuthCodeURL redirect_uri mismatch: got %q\n", query.Get("redirect_uri"))
		os.Exit(1)
	}
	if query.Get("response_type") != "code" {
		fmt.Fprintf(os.Stderr, "AuthCodeURL response_type mismatch: got %q, want 'code'\n", query.Get("response_type"))
		os.Exit(1)
	}
	if !strings.Contains(query.Get("scope"), "read") || !strings.Contains(query.Get("scope"), "write") {
		fmt.Fprintf(os.Stderr, "AuthCodeURL scope missing expected scopes: got %q\n", query.Get("scope"))
		os.Exit(1)
	}

	// 2. Setup mock OAuth2 token and resource server for Exchange and Client tests
	var tokenRequests []*http.Request
	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		switch r.URL.Path {
		case "/token":
			_ = r.ParseForm()
			grantType := r.Form.Get("grant_type")
			if grantType == "authorization_code" {
				code := r.Form.Get("code")
				if code == "valid-auth-code-123" {
					w.Header().Set("Content-Type", "application/json")
					_ = json.NewEncoder(w).Encode(map[string]interface{}{
						"access_token":  "access-token-live-abc",
						"token_type":    "Bearer",
						"refresh_token": "refresh-token-live-xyz",
						"expires_in":    3600,
					})
					return
				}
				w.Header().Set("Content-Type", "application/json")
				w.WriteHeader(http.StatusBadRequest)
				_ = json.NewEncoder(w).Encode(map[string]interface{}{
					"error":             "invalid_grant",
					"error_description": "code is invalid or expired",
				})
				return
			} else if grantType == "refresh_token" {
				refreshToken := r.Form.Get("refresh_token")
				if refreshToken == "refresh-token-live-xyz" {
					w.Header().Set("Content-Type", "application/json")
					_ = json.NewEncoder(w).Encode(map[string]interface{}{
						"access_token":  "access-token-refreshed-789",
						"token_type":    "Bearer",
						"refresh_token": "refresh-token-live-xyz",
						"expires_in":    3600,
					})
					return
				}
				w.WriteHeader(http.StatusBadRequest)
				return
			}
			w.WriteHeader(http.StatusBadRequest)

		case "/protected/profile":
			authHeader := r.Header.Get("Authorization")
			if authHeader == "Bearer access-token-live-abc" {
				w.Header().Set("Content-Type", "application/json")
				_, _ = io.WriteString(w, `{"id":"user-100","status":"active"}`)
				return
			}
			w.WriteHeader(http.StatusUnauthorized)

		default:
			http.NotFound(w, r)
		}
	}))
	defer ts.Close()

	serverConf := &oauth2.Config{
		ClientID:     "mock-client-id",
		ClientSecret: "mock-client-secret",
		Endpoint: oauth2.Endpoint{
			AuthURL:  ts.URL + "/authorize",
			TokenURL: ts.URL + "/token",
		},
	}

	// 2. oauth2.Config.Exchange exchanges authorization code for Token with access_token, token_type, and expiry from token server
	tok, err := serverConf.Exchange(ctx, "valid-auth-code-123")
	if err != nil {
		fmt.Fprintf(os.Stderr, "Exchange failed for valid code: %v\n", err)
		os.Exit(1)
	}
	if tok.AccessToken != "access-token-live-abc" {
		fmt.Fprintf(os.Stderr, "Exchange access_token mismatch: got %q\n", tok.AccessToken)
		os.Exit(1)
	}
	if tok.TokenType != "Bearer" {
		fmt.Fprintf(os.Stderr, "Exchange token_type mismatch: got %q\n", tok.TokenType)
		os.Exit(1)
	}
	if tok.RefreshToken != "refresh-token-live-xyz" {
		fmt.Fprintf(os.Stderr, "Exchange refresh_token mismatch: got %q\n", tok.RefreshToken)
		os.Exit(1)
	}
	if !tok.Valid() {
		fmt.Fprintf(os.Stderr, "Exchange token expected to be valid, got invalid\n")
		os.Exit(1)
	}

	// 3. oauth2.Config.Exchange returns error when token server responds with HTTP error or invalid grant
	_, err = serverConf.Exchange(ctx, "bad-code-999")
	if err == nil {
		fmt.Fprintf(os.Stderr, "Exchange expected error for invalid code, got nil\n")
		os.Exit(1)
	}
	var retrieveErr *oauth2.RetrieveError
	if !strings.Contains(err.Error(), "invalid_grant") && !strings.Contains(err.Error(), "oauth2: cannot fetch token") {
		fmt.Fprintf(os.Stderr, "Exchange returned unexpected error format: %v\n", err)
		os.Exit(1)
	}

	// 4. oauth2.Config.Client creates an http.Client whose transport adds Authorization Bearer header with the access token
	client := serverConf.Client(ctx, tok)
	resp, err := client.Get(ts.URL + "/protected/profile")
	if err != nil {
		fmt.Fprintf(os.Stderr, "Client.Get failed: %v\n", err)
		os.Exit(1)
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusOK {
		fmt.Fprintf(os.Stderr, "Client.Get status code mismatch: got %d, want 200\n", resp.StatusCode)
		os.Exit(1)
	}
	respBytes, err := io.ReadAll(resp.Body)
	if err != nil || !strings.Contains(string(respBytes), `"user-100"`) {
		fmt.Fprintf(os.Stderr, "Client.Get response body mismatch: %s\n", string(respBytes))
		os.Exit(1)
	}

	// 5. oauth2.Token.Valid returns true for non-empty unexpired token and false for expired token
	expiredTok := &oauth2.Token{
		AccessToken:  "expired-token-123",
		TokenType:    "Bearer",
		RefreshToken: "refresh-token-live-xyz",
		Expiry:       time.Now().Add(-10 * time.Minute),
	}
	if expiredTok.Valid() {
		fmt.Fprintf(os.Stderr, "expiredTok.Valid() expected false, got true\n")
		os.Exit(1)
	}
	futureTok := &oauth2.Token{
		AccessToken: "future-token-123",
		TokenType:   "Bearer",
		Expiry:      time.Now().Add(10 * time.Minute),
	}
	if !futureTok.Valid() {
		fmt.Fprintf(os.Stderr, "futureTok.Valid() expected true, got false\n")
		os.Exit(1)
	}

	// 6. oauth2.Config.TokenSource returns a TokenSource that automatically refreshes an expired token using refresh_token
	tokenSource := serverConf.TokenSource(ctx, expiredTok)
	refreshedTok, err := tokenSource.Token()
	if err != nil {
		fmt.Fprintf(os.Stderr, "TokenSource failed to refresh token: %v\n", err)
		os.Exit(1)
	}
	if refreshedTok.AccessToken != "access-token-refreshed-789" {
		fmt.Fprintf(os.Stderr, "Refreshed token access_token mismatch: got %q\n", refreshedTok.AccessToken)
		os.Exit(1)
	}
	if !refreshedTok.Valid() {
		fmt.Fprintf(os.Stderr, "Refreshed token should be valid\n")
		os.Exit(1)
	}

	_ = tokenRequests
	_ = retrieveErr

	fmt.Println("All oauth2 contract assertions passed.")
}