add providers resolver

go.mod

@@ -1,41 +1,20 @@
 module github.com/markbates/goth
 
-go 1.18
+go 1.15
 
 require (
 	github.com/golang-jwt/jwt/v4 v4.2.0
 	github.com/gorilla/mux v1.6.2
 	github.com/gorilla/pat v0.0.0-20180118222023-199c85a7f6d1
 	github.com/gorilla/sessions v1.1.1
 	github.com/jarcoal/httpmock v0.0.0-20180424175123-9c70cfe4a1da
+	github.com/kr/pretty v0.3.1 // indirect
 	github.com/lestrrat-go/jwx v1.2.28
 	github.com/markbates/going v1.0.0
 	github.com/mrjones/oauth v0.0.0-20180629183705-f4e24b6d100c
+	github.com/rogpeppe/go-internal v1.12.0 // indirect
 	github.com/stretchr/testify v1.8.4
 	golang.org/x/oauth2 v0.17.0
-)
-
-require (
-	cloud.google.com/go/compute v1.20.1 // indirect
-	cloud.google.com/go/compute/metadata v0.2.3 // indirect
-	github.com/davecgh/go-spew v1.1.1 // indirect
-	github.com/decred/dcrd/dcrec/secp256k1/v4 v4.2.0 // indirect
-	github.com/goccy/go-json v0.10.2 // indirect
-	github.com/golang/protobuf v1.5.3 // indirect
-	github.com/gorilla/context v1.1.1 // indirect
-	github.com/gorilla/securecookie v1.1.1 // indirect
-	github.com/kr/pretty v0.3.1 // indirect
-	github.com/lestrrat-go/backoff/v2 v2.0.8 // indirect
-	github.com/lestrrat-go/blackmagic v1.0.2 // indirect
-	github.com/lestrrat-go/httpcc v1.0.1 // indirect
-	github.com/lestrrat-go/iter v1.0.2 // indirect
-	github.com/lestrrat-go/option v1.0.1 // indirect
-	github.com/pkg/errors v0.9.1 // indirect
-	github.com/pmezard/go-difflib v1.0.0 // indirect
-	github.com/rogpeppe/go-internal v1.12.0 // indirect
-	golang.org/x/crypto v0.19.0 // indirect
 	google.golang.org/appengine v1.6.8 // indirect
 	google.golang.org/protobuf v1.32.0 // indirect
-	gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c // indirect
-	gopkg.in/yaml.v3 v3.0.1 // indirect
 )

provider.go

@@ -26,36 +26,66 @@ const NoAuthUrlErrorMessage = "an AuthURL has not been set"
 // Providers is list of known/available providers.
 type Providers map[string]Provider
 
-var providers = Providers{}
+// ProviderResolver an interface to resolve a provider by name
+type ProviderResolver interface {
+	Get(name string) (Provider, error)
+	GetAll() Providers
+}
+
+// DefaultProviderResolver default implementation of ProviderResolver to resolve a provider from a static map
+type DefaultProviderResolver struct {
+	providers map[string]Provider
+}
+
+var resolver ProviderResolver
+
+// ResolveProvider returns a previously created provider. If Goth has not
+// been told to use the named provider it will return an error.
+func (r DefaultProviderResolver) Get(name string) (Provider, error) {
+	provider := r.providers[name]
+	if provider == nil {
+		return nil, fmt.Errorf("no provider for %s exists", name)
+	}
+	return provider, nil
+}
+
+// ResolveProvider returns a previously created provider. If Goth has not
+// been told to use the named provider it will return an error.
+func (r DefaultProviderResolver) GetAll() Providers {
+	return r.providers
+}
 
 // UseProviders adds a list of available providers for use with Goth.
 // Can be called multiple times. If you pass the same provider more
 // than once, the last will be used.
 func UseProviders(viders ...Provider) {
-	for _, provider := range viders {
-		providers[provider.Name()] = provider
+	providers := Providers{}
+	for _, p := range viders {
+		providers[p.Name()] = p
 	}
+	resolver = DefaultProviderResolver{providers: providers}
+}
+
+// SetProviderResolver set the active resolver.
+func SetProviderResolver(r ProviderResolver) {
+	resolver = r
 }
 
 // GetProviders returns a list of all the providers currently in use.
 func GetProviders() Providers {
-	return providers
+	return resolver.GetAll()
 }
 
 // GetProvider returns a previously created provider. If Goth has not
 // been told to use the named provider it will return an error.
 func GetProvider(name string) (Provider, error) {
-	provider := providers[name]
-	if provider == nil {
-		return nil, fmt.Errorf("no provider for %s exists", name)
-	}
-	return provider, nil
+	return resolver.Get(name)
 }
 
 // ClearProviders will remove all providers currently in use.
 // This is useful, mostly, for testing purposes.
 func ClearProviders() {
-	providers = Providers{}
+	resolver = nil
 }
 
 // ContextForClient provides a context for use with oauth2.

provider_test.go

@@ -33,3 +33,36 @@ func Test_GetProvider(t *testing.T) {
 	a.Equal(err.Error(), "no provider for unknown exists")
 	goth.ClearProviders()
 }
+
+func Test_CustomResolver(t *testing.T) {
+	a := assert.New(t)
+	resolver := &CustomResolver{}
+	goth.SetProviderResolver(resolver)
+	p, err := goth.GetProvider("faux")
+	a.NoError(err)
+	a.Equal(len(goth.GetProviders()), 1)
+	a.NotNil(p)
+
+	p, err = goth.GetProvider("unknown")
+	a.NoError(err)
+	a.Nil(p)
+
+	goth.ClearProviders()
+}
+
+type CustomResolver struct{}
+
+func (r CustomResolver) Get(name string) (goth.Provider, error) {
+	// you can load this from a database or something
+	if name != "faux" {
+		return nil, nil
+	}
+	return &faux.Provider{}, nil
+}
+
+func (r CustomResolver) GetAll() goth.Providers {
+	// you can load this from a database or something
+	return goth.Providers{
+		"faux": &faux.Provider{},
+	}
+}