tests: e2e: reloading of the .env file

e2e/README.md

@@ -1,6 +1,7 @@
 # End-to-end tests
 
-Tests of the drivers with the real external systems: Consul, Vault and etcd.
+Tests of the drivers with the real external systems: Consul, Vault and etcd,
+and the scenarios of a service with several drivers: the yaml file, the `.env` file and the process environment.
 The systems are started in Docker by [testcontainers](https://golang.testcontainers.org/), so only Docker is needed:
 
 ```sh

e2e/dotenv_test.go

@@ -0,0 +1,130 @@
+package e2e
+
+import (
+	"context"
+	"os"
+	"path/filepath"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/insei/tinyconf/v2"
+	"github.com/insei/tinyconf/v2/drivers/env"
+	"github.com/insei/tinyconf/v2/drivers/tag"
+	"github.com/insei/tinyconf/v2/drivers/yaml"
+)
+
+type dotenvHTTP struct {
+	Host string `yaml:"host" env:"E2E_DOTENV_HTTP_HOST" default:"localhost"`
+	Port int    `yaml:"port" env:"E2E_DOTENV_HTTP_PORT" default:"8080"`
+}
+
+type dotenvDatabase struct {
+	Pool     int    `yaml:"pool" env:"E2E_DOTENV_DB_POOL"`
+	Password string `env:"E2E_DOTENV_DB_PASSWORD"`
+}
+
+type dotenvConfig struct {
+	HTTP     dotenvHTTP     `yaml:"http"`
+	Database dotenvDatabase `yaml:"database"`
+}
+
+// TestDotenv is the config of a service from the defaults, the yaml file, the .env file and the process environment,
+// the changes of the .env file are reloaded without restart.
+func TestDotenv(t *testing.T) {
+	exported := []string{"E2E_DOTENV_HTTP_HOST", "E2E_DOTENV_HTTP_PORT", "E2E_DOTENV_DB_PASSWORD"}
+	for _, key := range exported {
+		require.NoError(t, os.Unsetenv(key))
+	}
+	t.Cleanup(func() {
+		for _, key := range exported {
+			_ = os.Unsetenv(key)
+		}
+	})
+	// the real environment of the process has priority over the .env file
+	t.Setenv("E2E_DOTENV_DB_POOL", "7")
+
+	dir := t.TempDir()
+	configFile, envFile := filepath.Join(dir, "config.yaml"), filepath.Join(dir, ".env")
+	write := func(file, content string) {
+		t.Helper()
+		require.NoError(t, os.WriteFile(file, []byte(content), 0o600))
+	}
+	write(configFile, "http:\n  host: yaml.example.com\ndatabase:\n  pool: 3\n")
+	write(envFile, "E2E_DOTENV_HTTP_PORT=9090\nE2E_DOTENV_DB_POOL=5\nE2E_DOTENV_DB_PASSWORD=first\n")
+
+	tagDriver, err := tag.New("default")
+	require.NoError(t, err)
+	yamlDriver, err := yaml.New(configFile, yaml.WithWatchInterval(100*time.Millisecond))
+	require.NoError(t, err)
+	envDriver, err := env.New(env.WithFiles(envFile), env.WithWatchInterval(100*time.Millisecond))
+	require.NoError(t, err)
+	manager := newManager(t, tagDriver, yamlDriver, envDriver)
+	conf := &dotenvConfig{}
+	require.NoError(t, manager.Register(conf))
+	require.NoError(t, manager.Parse(context.Background(), conf))
+	assert.Equal(t, dotenvConfig{
+		HTTP:     dotenvHTTP{Host: "yaml.example.com", Port: 9090},
+		Database: dotenvDatabase{Pool: 7, Password: "first"},
+	}, *conf)
+	assert.Equal(t, "9090", os.Getenv("E2E_DOTENV_HTTP_PORT"))
+
+	// reloaded checks that the change is reloaded, when the subscribers are not called
+	reloaded := func(t *testing.T, since time.Time) {
+		t.Helper()
+		assert.True(t, manager.ReloadStatus().LastReload.After(since), "change is not reloaded")
+	}
+
+	https := subscribe[dotenvHTTP](t, manager)
+	databases := subscribe[dotenvDatabase](t, manager)
+
+	t.Run("change of the .env file reloads only its part", func(t *testing.T) {
+		write(envFile, "E2E_DOTENV_HTTP_PORT=9191\nE2E_DOTENV_DB_POOL=5\nE2E_DOTENV_DB_PASSWORD=first\n")
+		assert.Equal(t, dotenvHTTP{Host: "yaml.example.com", Port: 9191}, *next(t, https))
+		noReload(t, databases)
+		assert.Equal(t, "9191", os.Getenv("E2E_DOTENV_HTTP_PORT"))
+	})
+
+	t.Run("the process environment keeps its values", func(t *testing.T) {
+		since := time.Now()
+		write(envFile, "E2E_DOTENV_HTTP_PORT=9191\nE2E_DOTENV_DB_POOL=50\nE2E_DOTENV_DB_PASSWORD=first\n")
+		noReload(t, databases)
+		reloaded(t, since)
+		assert.Equal(t, "7", os.Getenv("E2E_DOTENV_DB_POOL"))
+		assert.Equal(t, 7, tinyconf.Current[dotenvDatabase](manager).Pool)
+	})
+
+	t.Run("variable removed from the .env file is removed from the environment", func(t *testing.T) {
+		write(envFile, "E2E_DOTENV_HTTP_PORT=9191\nE2E_DOTENV_DB_POOL=50\n")
+		assert.Equal(t, dotenvDatabase{Pool: 7}, *next(t, databases))
+		_, exist := os.LookupEnv("E2E_DOTENV_DB_PASSWORD")
+		assert.False(t, exist)
+	})
+
+	t.Run("variable added to the .env file overrides the yaml file", func(t *testing.T) {
+		write(envFile, "E2E_DOTENV_HTTP_PORT=9191\nE2E_DOTENV_DB_POOL=50\nE2E_DOTENV_HTTP_HOST=env.example.com\n")
+		assert.Equal(t, dotenvHTTP{Host: "env.example.com", Port: 9191}, *next(t, https))
+	})
+
+	t.Run("change of the yaml file under the .env value", func(t *testing.T) {
+		since := time.Now()
+		write(configFile, "http:\n  host: new.example.com\ndatabase:\n  pool: 4\n")
+		noReload(t, https)
+		noReload(t, databases)
+		reloaded(t, since)
+	})
+
+	t.Run("broken .env file keeps the current version", func(t *testing.T) {
+		require.NoError(t, os.Remove(envFile))
+		noReload(t, https)
+		assert.Error(t, manager.ReloadStatus().LastError)
+
+		write(envFile, "E2E_DOTENV_HTTP_PORT=9292\n")
+		assert.Equal(t, dotenvHTTP{Host: "new.example.com", Port: 9292}, *next(t, https))
+	})
+
+	// the config of the application is never changed by reloads
+	assert.Equal(t, 9090, conf.HTTP.Port)
+}