Firebase App auto init (#54)

* FIREBASE_CONFIG env variable auto init, allows calling initialize_app with not arguments using the env variable

* allow env var to contain json

* add tests for json string in env file

Author: avishalom

firebase.go

@@ -18,7 +18,10 @@
 package firebase
 
 import (
+	"encoding/json"
 	"errors"
+	"io/ioutil"
+	"os"
 
 	"cloud.google.com/go/firestore"
 
@@ -27,8 +30,6 @@ import (
 	"firebase.google.com/go/internal"
 	"firebase.google.com/go/storage"
 
-	"os"
-
 	"golang.org/x/net/context"
 	"golang.org/x/oauth2/google"
 	"google.golang.org/api/option"
@@ -47,6 +48,9 @@ var firebaseScopes = []string{
 // Version of the Firebase Go Admin SDK.
 const Version = "2.3.0"
 
+// firebaseEnvName is the name of the environment variable with the Config.
+const firebaseEnvName = "FIREBASE_CONFIG"
+
 // An App holds configuration and state common to all Firebase services that are exposed from the SDK.
 type App struct {
 	creds         *google.DefaultCredentials
@@ -57,8 +61,8 @@ type App struct {
 
 // Config represents the configuration used to initialize an App.
 type Config struct {
-	ProjectID     string
-	StorageBucket string
+	ProjectID     string `json:"projectId"`
+	StorageBucket string `json:"storageBucket"`
 }
 
 // Auth returns an instance of auth.Client.
@@ -107,14 +111,14 @@ func (a *App) InstanceID(ctx context.Context) (*iid.Client, error) {
 func NewApp(ctx context.Context, config *Config, opts ...option.ClientOption) (*App, error) {
 	o := []option.ClientOption{option.WithScopes(firebaseScopes...)}
 	o = append(o, opts...)
-
 	creds, err := transport.Creds(ctx, o...)
 	if err != nil {
 		return nil, err
 	}
-
 	if config == nil {
-		config = &Config{}
+		if config, err = getConfigDefaults(); err != nil {
+			return nil, err
+		}
 	}
 
 	var pid string
@@ -133,3 +137,24 @@ func NewApp(ctx context.Context, config *Config, opts ...option.ClientOption) (*
 		opts:          o,
 	}, nil
 }
+
+// getConfigDefaults reads the default config file, defined by the FIREBASE_CONFIG
+// env variable, used only when options are nil.
+func getConfigDefaults() (*Config, error) {
+	fbc := &Config{}
+	confFileName := os.Getenv(firebaseEnvName)
+	if confFileName == "" {
+		return fbc, nil
+	}
+	var dat []byte
+	if confFileName[0] == byte('{') {
+		dat = []byte(confFileName)
+	} else {
+		var err error
+		if dat, err = ioutil.ReadFile(confFileName); err != nil {
+			return nil, err
+		}
+	}
+	err := json.Unmarshal(dat, fbc)
+	return fbc, err
+}

firebase_test.go

@@ -16,6 +16,7 @@ package firebase
 
 import (
 	"io/ioutil"
+	"log"
 	"net/http"
 	"net/http/httptest"
 	"os"
@@ -35,6 +36,17 @@ import (
 	"google.golang.org/api/option"
 )
 
+const credEnvVar = "GOOGLE_APPLICATION_CREDENTIALS"
+
+func TestMain(m *testing.M) {
+	// This isolates the tests from a possiblity that the default config env
+	// variable is set to a valid file containing the wanted default config,
+	// but we the test is not expecting it.
+	configOld := overwriteEnv(firebaseEnvName, "")
+	defer reinstateEnv(firebaseEnvName, configOld)
+	os.Exit(m.Run())
+}
+
 func TestServiceAcctFile(t *testing.T) {
 	app, err := NewApp(context.Background(), nil, option.WithCredentialsFile("testdata/service_account.json"))
 	if err != nil {
@@ -151,13 +163,12 @@ func TestRefreshTokenWithEnvVar(t *testing.T) {
 }
 
 func TestAppDefault(t *testing.T) {
-	varName := "GOOGLE_APPLICATION_CREDENTIALS"
-	current := os.Getenv(varName)
+	current := os.Getenv(credEnvVar)
 
-	if err := os.Setenv(varName, "testdata/service_account.json"); err != nil {
+	if err := os.Setenv(credEnvVar, "testdata/service_account.json"); err != nil {
 		t.Fatal(err)
 	}
-	defer os.Setenv(varName, current)
+	defer os.Setenv(credEnvVar, current)
 
 	app, err := NewApp(context.Background(), nil)
 	if err != nil {
@@ -175,13 +186,12 @@ func TestAppDefault(t *testing.T) {
 }
 
 func TestAppDefaultWithInvalidFile(t *testing.T) {
-	varName := "GOOGLE_APPLICATION_CREDENTIALS"
-	current := os.Getenv(varName)
+	current := os.Getenv(credEnvVar)
 
-	if err := os.Setenv(varName, "testdata/non_existing.json"); err != nil {
+	if err := os.Setenv(credEnvVar, "testdata/non_existing.json"); err != nil {
 		t.Fatal(err)
 	}
-	defer os.Setenv(varName, current)
+	defer os.Setenv(credEnvVar, current)
 
 	app, err := NewApp(context.Background(), nil)
 	if app != nil || err == nil {
@@ -337,6 +347,139 @@ func TestVersion(t *testing.T) {
 		}
 	}
 }
+func TestAutoInit(t *testing.T) {
+	tests := []struct {
+		name          string
+		optionsConfig string
+		initOptions   *Config
+		wantOptions   *Config
+	}{
+		{
+			"No environment variable, no explicit options",
+			"",
+			nil,
+			&Config{ProjectID: "mock-project-id"}, // from default creds here and below.
+		}, {
+			"Environment variable set to file, no explicit options",
+			"testdata/firebase_config.json",
+			nil,
+			&Config{
+				ProjectID:     "hipster-chat-mock",
+				StorageBucket: "hipster-chat.appspot.mock",
+			},
+		}, {
+			"Environment variable set to string, no explicit options",
+			`{
+				"projectId": "hipster-chat-mock",
+				"storageBucket": "hipster-chat.appspot.mock"
+			  }`,
+			nil,
+			&Config{
+				ProjectID:     "hipster-chat-mock",
+				StorageBucket: "hipster-chat.appspot.mock",
+			},
+		}, {
+			"Environment variable set to file with some values missing, no explicit options",
+			"testdata/firebase_config_partial.json",
+			nil,
+			&Config{ProjectID: "hipster-chat-mock"},
+		}, {
+			"Environment variable set to string with some values missing, no explicit options",
+			`{"projectId": "hipster-chat-mock"}`,
+			nil,
+			&Config{ProjectID: "hipster-chat-mock"},
+		}, {
+			"Environment variable set to file which is ignored as some explicit options are passed",
+			"testdata/firebase_config_partial.json",
+			&Config{StorageBucket: "sb1-mock"},
+			&Config{
+				ProjectID:     "mock-project-id",
+				StorageBucket: "sb1-mock",
+			},
+		}, {
+			"Environment variable set to string which is ignored as some explicit options are passed",
+			`{"projectId": "hipster-chat-mock"}`,
+			&Config{StorageBucket: "sb1-mock"},
+			&Config{
+				ProjectID:     "mock-project-id",
+				StorageBucket: "sb1-mock",
+			},
+		}, {
+			"Environment variable set to file which is ignored as options are explicitly empty",
+			"testdata/firebase_config_partial.json",
+			&Config{},
+			&Config{ProjectID: "mock-project-id"},
+		}, {
+			"Environment variable set to file with an unknown key which is ignored, no explicit options",
+			"testdata/firebase_config_invalid_key.json",
+			nil,
+			&Config{
+				ProjectID:     "mock-project-id", // from default creds
+				StorageBucket: "hipster-chat.appspot.mock",
+			},
+		}, {
+			"Environment variable set to string with an unknown key which is ignored, no explicit options",
+			`{
+				"obviously_bad_key": "hipster-chat-mock",
+				"storageBucket": "hipster-chat.appspot.mock"
+			}`,
+			nil,
+			&Config{
+				ProjectID:     "mock-project-id",
+				StorageBucket: "hipster-chat.appspot.mock",
+			},
+		},
+	}
+
+	credOld := overwriteEnv(credEnvVar, "testdata/service_account.json")
+	defer reinstateEnv(credEnvVar, credOld)
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			overwriteEnv(firebaseEnvName, test.optionsConfig)
+			app, err := NewApp(context.Background(), test.initOptions)
+			if err != nil {
+				t.Error(err)
+			} else {
+				compareConfig(app, test.wantOptions, t)
+			}
+		})
+	}
+}
+
+func TestAutoInitInvalidFiles(t *testing.T) {
+	tests := []struct {
+		name      string
+		filename  string
+		wantError string
+	}{
+		{
+			"nonexistant file",
+			"testdata/no_such_file.json",
+			"open testdata/no_such_file.json: no such file or directory",
+		}, {
+			"invalid JSON",
+			"testdata/firebase_config_invalid.json",
+			"invalid character 'b' looking for beginning of value",
+		}, {
+			"empty file",
+			"testdata/firebase_config_empty.json",
+			"unexpected end of JSON input",
+		},
+	}
+	credOld := overwriteEnv(credEnvVar, "testdata/service_account.json")
+	defer reinstateEnv(credEnvVar, credOld)
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			overwriteEnv(firebaseEnvName, test.filename)
+			_, err := NewApp(context.Background(), nil)
+			if err == nil || err.Error() != test.wantError {
+				t.Errorf("got error = %s; want = %s", err, test.wantError)
+			}
+		})
+	}
+}
 
 type testTokenSource struct {
 	AccessToken string
@@ -350,6 +493,15 @@ func (t *testTokenSource) Token() (*oauth2.Token, error) {
 	}, nil
 }
 
+func compareConfig(got *App, want *Config, t *testing.T) {
+	if got.projectID != want.ProjectID {
+		t.Errorf("app.projectID = %q; want = %q", got.projectID, want.ProjectID)
+	}
+	if got.storageBucket != want.StorageBucket {
+		t.Errorf("app.storageBucket = %q; want = %q", got.storageBucket, want.StorageBucket)
+	}
+}
+
 // mockServiceAcct generates a service account configuration with the provided URL as the
 // token_url value.
 func mockServiceAcct(tokenURL string) ([]byte, error) {
@@ -379,3 +531,25 @@ func initMockTokenServer() *httptest.Server {
 		}`))
 	}))
 }
+
+// overwriteEnv overwrites env variables, used in testsing.
+func overwriteEnv(varName, newVal string) string {
+	oldVal := os.Getenv(varName)
+	if newVal == "" {
+		if err := os.Unsetenv(varName); err != nil {
+			log.Fatal(err)
+		}
+	} else if err := os.Setenv(varName, newVal); err != nil {
+		log.Fatal(err)
+	}
+	return oldVal
+}
+
+// reinstateEnv restores the enviornment variable, will usually be used deferred with overwriteEnv.
+func reinstateEnv(varName, oldVal string) {
+	if len(varName) > 0 {
+		os.Setenv(varName, oldVal)
+	} else {
+		os.Unsetenv(varName)
+	}
+}

testdata/firebase_config.json

@@ -0,0 +1,4 @@
+{
+  "projectId": "hipster-chat-mock",
+  "storageBucket": "hipster-chat.appspot.mock"
+}

testdata/firebase_config_empty.json

@@ -0,0 +1 @@
+baaad

testdata/firebase_config_invalid.json

@@ -0,0 +1,4 @@
+{
+  "project1d_bad_key": "hipster-chat-mock",
+  "storageBucket": "hipster-chat.appspot.mock"
+}

testdata/firebase_config_invalid_key.json

@@ -0,0 +1,3 @@
+{
+  "projectId": "hipster-chat-mock"
+}