Add Cacher interface.

oauth2.go

@@ -22,6 +22,18 @@ import (
 	"strings"
 )
 
+// Cacher implementations read and write OAuth 2.0 tokens from a cache.
+type Cacher interface {
+	// Read reads the token from the cache.
+	// If the read is successful, it should return the token and a nil error.
+	// The returned tokens may be expired tokens.
+	// If there is no token in the cache, it should return a nil token and a nil error.
+	// It should return a non-nil error when an unrecoverable failure occurs.
+	Read() (*Token, error)
+	// Write writes the token to the cache.
+	Write(*Token)
+}
+
 // Option represents a function that applies some state to
 // an Options object.
 type Option func(*Options) error
@@ -91,6 +103,16 @@ func RoundTripper(tr http.RoundTripper) Option {
 	}
 }
 
+// Cache requires a Cacher implementation. It will initially read
+// the token if the transport is initialized with NewTransportFromCache
+// and will write the refreshed tokens back to the cache.
+func Cache(c Cacher) Option {
+	return func(o *Options) error {
+		o.Cache = c
+		return nil
+	}
+}
+
 type Flow struct {
 	opts Options
 }
@@ -109,11 +131,11 @@ func New(options ...Option) (*Flow, error) {
 	case f.opts.TokenFetcherFunc != nil:
 		return f, nil
 	case f.opts.AUD != nil:
-		// TODO(jbd): Assert required JWT params.
+		// TODO(jbd): Assert the required JWT params.
 		f.opts.TokenFetcherFunc = makeTwoLeggedFetcher(&f.opts)
 		return f, nil
 	case f.opts.AuthURL != nil && f.opts.TokenURL != nil:
-		// TODO(jbd): Assert required OAuth2 params.
+		// TODO(jbd): Assert the required OAuth2 params.
 		f.opts.TokenFetcherFunc = makeThreeLeggedFetcher(&f.opts)
 		return f, nil
 	default:
@@ -175,6 +197,23 @@ func (f *Flow) exchange(code string) (*Token, error) {
 	})
 }
 
+// NewTransportFromCache reads the token from the cache and returns
+// a Transport that is authorized and the authenticated
+// by the returned token.
+func (f *Flow) NewTransportFromCache() (*Transport, error) {
+	if f.opts.Cache == nil {
+		return nil, errors.New("oauth2: no cache is set")
+	}
+	tok, err := f.opts.Cache.Read()
+	if err != nil {
+		return nil, err
+	}
+	if tok == nil {
+		return nil, nil
+	}
+	return f.newTransportFromToken(tok), nil
+}
+
 // NewTransportFromCode exchanges the code to retrieve a new access token
 // and returns an authorized and authenticated Transport.
 func (f *Flow) NewTransportFromCode(code string) (*Transport, error) {
@@ -182,22 +221,22 @@ func (f *Flow) NewTransportFromCode(code string) (*Transport, error) {
 	if err != nil {
 		return nil, err
 	}
-	return f.NewTransportFromToken(token), nil
-}
-
-// NewTransportFromToken returns a new Transport that is authorized
-// and authenticated with the provided token.
-func (f *Flow) NewTransportFromToken(t *Token) *Transport {
-	tr := f.opts.Transport
-	if tr == nil {
-		tr = http.DefaultTransport
-	}
-	return newTransport(tr, f.opts.TokenFetcherFunc, t)
+	return f.newTransportFromToken(token), nil
 }
 
 // NewTransport returns a Transport.
 func (f *Flow) NewTransport() *Transport {
-	return f.NewTransportFromToken(nil)
+	return f.newTransportFromToken(nil)
+}
+
+// newTransportFromToken returns a new Transport that is authorized
+// and authenticated with the provided token.
+func (f *Flow) newTransportFromToken(t *Token) *Transport {
+	tr := f.opts.Transport
+	if tr == nil {
+		tr = http.DefaultTransport
+	}
+	return newTransport(tr, &f.opts, t)
 }
 
 func makeThreeLeggedFetcher(o *Options) func(t *Token) (*Token, error) {
@@ -255,6 +294,8 @@ type Options struct {
 	// AUD represents the token endpoint required to complete the 2-legged JWT flow.
 	AUD *url.URL
 
+	Cache Cacher
+
 	TokenFetcherFunc func(t *Token) (*Token, error)
 
 	Transport http.RoundTripper

oauth2_test.go

@@ -20,6 +20,19 @@ func (t *mockTransport) RoundTrip(req *http.Request) (resp *http.Response, err e
 	return t.rt(req)
 }
 
+type mockCache struct {
+	token   *Token
+	readErr error
+}
+
+func (c *mockCache) Read() (*Token, error) {
+	return c.token, c.readErr
+}
+
+func (c *mockCache) Write(*Token) {
+	// do nothing
+}
+
 func newTestFlow(url string) *Flow {
 	f, _ := New(
 		Client("CLIENT_ID", "CLIENT_SECRET"),
@@ -211,7 +224,8 @@ func TestTokenRefreshRequest(t *testing.T) {
 	}))
 	defer ts.Close()
 	f := newTestFlow(ts.URL)
-	tr := f.NewTransportFromToken(&Token{RefreshToken: "REFRESH_TOKEN"})
+	tr := f.NewTransport()
+	tr.SetToken(&Token{RefreshToken: "REFRESH_TOKEN"})
 	c := http.Client{Transport: tr}
 	c.Get(ts.URL + "/somethingelse")
 }
@@ -235,10 +249,25 @@ func TestFetchWithNoRefreshToken(t *testing.T) {
 	}))
 	defer ts.Close()
 	f := newTestFlow(ts.URL)
-	tr := f.NewTransportFromToken(&Token{})
+	tr := f.NewTransport()
 	c := http.Client{Transport: tr}
 	_, err := c.Get(ts.URL + "/somethingelse")
 	if err == nil {
 		t.Errorf("Fetch should return an error if no refresh token is set")
 	}
 }
+
+func TestCacheNoToken(t *testing.T) {
+	f, _ := New(
+		Client("CLIENT_ID", "CLIENT_SECRET"),
+		Endpoint("/auth", "/token"),
+		Cache(&mockCache{token: nil, readErr: nil}),
+	)
+	tr, err := f.NewTransportFromCache()
+	if err != nil {
+		t.Errorf("No error expected, %v is found", err)
+	}
+	if tr != nil {
+		t.Errorf("No transport should have been initiated, tr is found to be %v", tr)
+	}
+}

transport.go

@@ -66,8 +66,8 @@ func (t *Token) Expired() bool {
 
 // Transport is an http.RoundTripper that makes OAuth 2.0 HTTP requests.
 type Transport struct {
-	fetcher func(t *Token) (*Token, error)
-	base    http.RoundTripper
+	opts *Options
+	base http.RoundTripper
 
 	mu    sync.RWMutex
 	token *Token
@@ -76,8 +76,12 @@ type Transport struct {
 // NewTransport creates a new Transport that uses the provided
 // token fetcher as token retrieving strategy. It authenticates
 // the requests and delegates origTransport to make the actual requests.
-func newTransport(base http.RoundTripper, fn func(t *Token) (*Token, error), token *Token) *Transport {
-	return &Transport{base: base, fetcher: fn, token: token}
+func newTransport(base http.RoundTripper, opts *Options, token *Token) *Transport {
+	return &Transport{
+		base:  base,
+		opts:  opts,
+		token: token,
+	}
 }
 
 // RoundTrip authorizes and authenticates the request with an
@@ -94,6 +98,9 @@ func (t *Transport) RoundTrip(req *http.Request) (resp *http.Response, err error
 			return nil, err
 		}
 		token = t.Token()
+		if t.opts.Cache != nil {
+			t.opts.Cache.Write(token)
+		}
 	}
 
 	// To set the Authorization header, we must make a copy of the Request
@@ -129,7 +136,7 @@ func (t *Transport) SetToken(v *Token) {
 func (t *Transport) RefreshToken() error {
 	t.mu.Lock()
 	defer t.mu.Unlock()
-	token, err := t.fetcher(t.token)
+	token, err := t.opts.TokenFetcherFunc(t.token)
 	if err != nil {
 		return err
 	}

transport_test.go

@@ -15,10 +15,6 @@ func (f *mockTokenFetcher) Fn() func(*Token) (*Token, error) {
 	}
 }
 
-func (f *mockTokenFetcher) FetchToken(existing *Token) (*Token, error) {
-	return f.token, nil
-}
-
 func TestInitialTokenRead(t *testing.T) {
 	tr := newTransport(http.DefaultTransport, nil, &Token{AccessToken: "abc"})
 	server := newMockServer(func(w http.ResponseWriter, r *http.Request) {
@@ -37,7 +33,7 @@ func TestTokenFetch(t *testing.T) {
 			AccessToken: "abc",
 		},
 	}
-	tr := newTransport(http.DefaultTransport, fetcher.Fn(), nil)
+	tr := newTransport(http.DefaultTransport, &Options{TokenFetcherFunc: fetcher.Fn()}, nil)
 	server := newMockServer(func(w http.ResponseWriter, r *http.Request) {
 		if r.Header.Get("Authorization") != "Bearer abc" {
 			t.Errorf("Transport doesn't set the Authorization header from the fetched token")