support --env-file CLI option (#274)

README.md

@@ -138,6 +138,7 @@ The following options are available with all commands. You must use command line
 
 - `--url, -u "protocol://host:port/dbname"` - specify the database url directly. _(env: `DATABASE_URL`)_
 - `--env, -e "DATABASE_URL"` - specify an environment variable to read the database connection URL from.
+- `--env-file ".env"` - specify an alternate environment variables file(s) to load.
 - `--migrations-dir, -d "./db/migrations"` - where to keep the migration files. _(env: `DBMATE_MIGRATIONS_DIR`)_
 - `--migrations-table "schema_migrations"` - database table to record migrations in. _(env: `DBMATE_MIGRATIONS_TABLE`)_
 - `--schema-file, -s "./db/schema.sql"` - a path to keep the schema.sql file. _(env: `DBMATE_SCHEMA_FILE`)_

fixtures/loadEnvFiles/.env

@@ -0,0 +1 @@
+TEST_DOTENV=default

fixtures/loadEnvFiles/.gitignore

@@ -0,0 +1 @@
+!.env

fixtures/loadEnvFiles/first.txt

@@ -0,0 +1 @@
+FIRST=one

fixtures/loadEnvFiles/invalid.txt

@@ -0,0 +1 @@
+INVALID ENV FILE

fixtures/loadEnvFiles/second.txt

@@ -0,0 +1 @@
+SECOND=two

main.go

@@ -1,8 +1,8 @@
 package main
 
 import (
+	"errors"
 	"fmt"
-	"log"
 	"net/url"
 	"os"
 	"regexp"
@@ -17,10 +17,14 @@ import (
 )
 
 func main() {
-	loadDotEnv()
+	err := loadEnvFiles(os.Args[1:])
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "Error: %v\n", err)
+		os.Exit(3)
+	}
 
 	app := NewApp()
-	err := app.Run(os.Args)
+	err = app.Run(os.Args)
 
 	if err != nil {
 		errText := redactLogString(fmt.Sprintf("Error: %s\n", err))
@@ -37,6 +41,7 @@ func NewApp() *cli.App {
 	app.Version = dbmate.Version
 
 	defaultDB := dbmate.New(nil)
+
 	app.Flags = []cli.Flag{
 		&cli.StringFlag{
 			Name:    "url",
@@ -49,6 +54,11 @@ func NewApp() *cli.App {
 			Value:   "DATABASE_URL",
 			Usage:   "specify an environment variable containing the database URL",
 		},
+		&cli.StringSliceFlag{
+			Name:  "env-file",
+			Value: cli.NewStringSlice(".env"),
+			Usage: "specify a file to load environment variables from",
+		},
 		&cli.StringSliceFlag{
 			Name:    "migrations-dir",
 			Aliases: []string{"d"},
@@ -211,15 +221,46 @@ func NewApp() *cli.App {
 	return app
 }
 
-// load environment variables from .env file
-func loadDotEnv() {
-	if _, err := os.Stat(".env"); err != nil {
-		return
+// load environment variables from file(s)
+func loadEnvFiles(args []string) error {
+	var envFiles []string
+
+	for i := 0; i < len(args); i++ {
+		if args[i] == "--env-file" {
+			if i+1 >= len(args) {
+				// returning nil here, even though it's an error
+				// because we want the caller to proceed anyway,
+				// and produce the actual arg parsing error response
+				return nil
+			}
+
+			envFiles = append(envFiles, args[i+1])
+			i++
+		}
+	}
+
+	if len(envFiles) == 0 {
+		envFiles = []string{".env"}
 	}
 
-	if err := godotenv.Load(); err != nil {
-		log.Fatalf("Error loading .env file: %s", err.Error())
+	// try to load all files in sequential order,
+	// ignoring any that do not exist
+	for _, file := range envFiles {
+		err := godotenv.Load([]string{file}...)
+		if err == nil {
+			continue
+		}
+
+		var perr *os.PathError
+		if errors.As(err, &perr) && errors.Is(perr, os.ErrNotExist) {
+			// Ignoring file not found error
+			continue
+		}
+
+		return fmt.Errorf("loading env file(s) %v: %v", envFiles, err)
 	}
+
+	return nil
 }
 
 // action wraps a cli.ActionFunc with dbmate initialization logic

main_test.go

@@ -3,6 +3,7 @@ package main
 import (
 	"flag"
 	"os"
+	"strings"
 	"testing"
 
 	"github.com/stretchr/testify/require"
@@ -58,3 +59,122 @@ func TestRedactLogString(t *testing.T) {
 		require.Equal(t, ex.expected, redactLogString(ex.in))
 	}
 }
+
+func TestLoadEnvFiles(t *testing.T) {
+	setup := func(t *testing.T) {
+		cwd, err := os.Getwd()
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		env := os.Environ()
+		os.Clearenv()
+
+		err = os.Chdir("fixtures/loadEnvFiles")
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		t.Cleanup(func() {
+			err := os.Chdir(cwd)
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			os.Clearenv()
+
+			for _, e := range env {
+				pair := strings.SplitN(e, "=", 2)
+				os.Setenv(pair[0], pair[1])
+			}
+		})
+	}
+
+	t.Run("default file is .env", func(t *testing.T) {
+		setup(t)
+
+		err := loadEnvFiles([]string{})
+		require.NoError(t, err)
+
+		require.Equal(t, 1, len(os.Environ()))
+		require.Equal(t, "default", os.Getenv("TEST_DOTENV"))
+	})
+
+	t.Run("valid file", func(t *testing.T) {
+		setup(t)
+
+		err := loadEnvFiles([]string{"--env-file", "first.txt"})
+		require.NoError(t, err)
+		require.Equal(t, 1, len(os.Environ()))
+		require.Equal(t, "one", os.Getenv("FIRST"))
+	})
+
+	t.Run("two valid files", func(t *testing.T) {
+		setup(t)
+
+		err := loadEnvFiles([]string{"--env-file", "first.txt", "--env-file", "second.txt"})
+		require.NoError(t, err)
+		require.Equal(t, 2, len(os.Environ()))
+		require.Equal(t, "one", os.Getenv("FIRST"))
+		require.Equal(t, "two", os.Getenv("SECOND"))
+	})
+
+	t.Run("nonexistent file", func(t *testing.T) {
+		setup(t)
+
+		err := loadEnvFiles([]string{"--env-file", "nonexistent.txt"})
+		require.NoError(t, err)
+		require.Equal(t, 0, len(os.Environ()))
+	})
+
+	t.Run("no overload", func(t *testing.T) {
+		setup(t)
+
+		// we do not load values over existing values
+		os.Setenv("FIRST", "not one")
+
+		err := loadEnvFiles([]string{"--env-file", "first.txt"})
+		require.NoError(t, err)
+		require.Equal(t, 1, len(os.Environ()))
+		require.Equal(t, "not one", os.Getenv("FIRST"))
+	})
+
+	t.Run("invalid file", func(t *testing.T) {
+		setup(t)
+
+		err := loadEnvFiles([]string{"--env-file", "invalid.txt"})
+		require.Error(t, err)
+		require.Contains(t, err.Error(), "unexpected character \"\\n\" in variable name near \"INVALID ENV FILE\\n\"")
+		require.Equal(t, 0, len(os.Environ()))
+	})
+
+	t.Run("invalid file followed by a valid file", func(t *testing.T) {
+		setup(t)
+
+		err := loadEnvFiles([]string{"--env-file", "invalid.txt", "--env-file", "first.txt"})
+		require.Error(t, err)
+		require.Contains(t, err.Error(), "unexpected character \"\\n\" in variable name near \"INVALID ENV FILE\\n\"")
+		require.Equal(t, 0, len(os.Environ()))
+	})
+
+	t.Run("valid file followed by an invalid file", func(t *testing.T) {
+		setup(t)
+
+		err := loadEnvFiles([]string{"--env-file", "first.txt", "--env-file", "invalid.txt"})
+		require.Error(t, err)
+		require.Contains(t, err.Error(), "unexpected character \"\\n\" in variable name near \"INVALID ENV FILE\\n\"")
+		require.Equal(t, 1, len(os.Environ()))
+		require.Equal(t, "one", os.Getenv("FIRST"))
+	})
+
+	t.Run("valid file followed by an invalid file followed by a valid file", func(t *testing.T) {
+		setup(t)
+
+		err := loadEnvFiles([]string{"--env-file", "first.txt", "--env-file", "invalid.txt", "--env-file", "second.txt"})
+		require.Error(t, err)
+		require.Contains(t, err.Error(), "unexpected character \"\\n\" in variable name near \"INVALID ENV FILE\\n\"")
+		// files after an invalid file should not get loaded
+		require.Equal(t, 1, len(os.Environ()))
+		require.Equal(t, "one", os.Getenv("FIRST"))
+	})
+}