Dev

README.md

@@ -1,6 +1,6 @@
 # dotenvgo
 
-[![Go Version](https://img.shields.io/badge/Go-1.21+-00ADD8?style=flat-square&logo=go)](https://golang.org)
+[![Go Version](https://img.shields.io/badge/Go-1.22+-00ADD8?style=flat-square&logo=go)](https://golang.org)
 [![License](https://img.shields.io/badge/License-MIT-blue.svg?style=flat-square)](LICENSE)
 [![Zero Dependencies](https://img.shields.io/badge/Dependencies-Zero-green?style=flat-square)](go.mod)
 [![Coverage](https://img.shields.io/badge/Coverage-91%25-brightgreen?style=flat-square)](https://github.com/godeh/dotenvgo)
@@ -13,6 +13,8 @@
 go get github.com/godeh/dotenvgo
 ```
 
+Requires Go 1.22 or newer.
+
 ## Quick Examples
 
 ### Type-Safe Variables
@@ -201,8 +203,13 @@ Pointer fields are supported during struct loading. For scalar pointer fields su
 KEY=value
 MESSAGE="Hello World"
 DEBUG=true # inline comment
+export PORT=8080
+
+# Multiline quoted values
+CERT="line1
+line2"
 
-# Variable expansion
+# Variable expansion (uses the current environment and variables loaded earlier in the file)
 BASE=/app
 CONFIG=${BASE}/config
 ```

dotenv_file.go

@@ -0,0 +1,182 @@
+package dotenvgo
+
+import (
+	"os"
+	"strings"
+)
+
+// LoadDotEnv loads environment variables from a .env file.
+// By default, it does NOT override existing environment variables.
+// Pass true as the second argument to override existing variables.
+//
+// Examples:
+//
+//	LoadDotEnv(".env")        // doesn't override existing vars
+//	LoadDotEnv(".env", false) // same as above
+//	LoadDotEnv(".env", true)  // overrides existing vars
+func LoadDotEnv(path string, override ...bool) error {
+	shouldOverride := false
+	if len(override) > 0 {
+		shouldOverride = override[0]
+	}
+	return loadDotEnvInternal(path, shouldOverride)
+}
+
+func loadDotEnvInternal(path string, override bool) error {
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return err
+	}
+
+	entries, err := parseDotEnvEntries(string(data))
+	if err != nil {
+		return err
+	}
+
+	resolved := make(map[string]string, len(entries))
+	for _, entry := range entries {
+		value := os.Expand(entry.value, func(name string) string {
+			if resolvedValue, ok := resolved[name]; ok {
+				return resolvedValue
+			}
+			envValue, _ := os.LookupEnv(name)
+			return envValue
+		})
+
+		if override {
+			_ = os.Setenv(entry.key, value)
+			resolved[entry.key] = value
+			continue
+		}
+
+		if existing, exists := os.LookupEnv(entry.key); exists {
+			resolved[entry.key] = existing
+			continue
+		}
+
+		_ = os.Setenv(entry.key, value)
+		resolved[entry.key] = value
+	}
+
+	return nil
+}
+
+type dotenvEntry struct {
+	key   string
+	value string
+}
+
+func parseDotEnvEntries(data string) ([]dotenvEntry, error) {
+	lines := strings.Split(data, "\n")
+	entries := make([]dotenvEntry, 0, len(lines))
+
+	for i := 0; i < len(lines); i++ {
+		line := strings.TrimSpace(lines[i])
+		if line == "" || strings.HasPrefix(line, "#") {
+			continue
+		}
+
+		if strings.HasPrefix(line, "export ") {
+			line = strings.TrimSpace(strings.TrimPrefix(line, "export "))
+		}
+
+		before, after, ok := strings.Cut(line, "=")
+		if !ok {
+			continue
+		}
+
+		key := strings.TrimSpace(before)
+		if key == "" {
+			continue
+		}
+
+		value, nextLine, err := parseDotEnvValue(lines, i, strings.TrimLeft(after, " \t"))
+		if err != nil {
+			return nil, err
+		}
+
+		entries = append(entries, dotenvEntry{key: key, value: value})
+		i = nextLine
+	}
+
+	return entries, nil
+}
+
+func parseDotEnvValue(lines []string, start int, valuePart string) (string, int, error) {
+	if valuePart == "" {
+		return "", start, nil
+	}
+
+	quote := valuePart[0]
+	if quote == '"' || quote == '\'' {
+		return parseQuotedDotEnvValue(lines, start, valuePart, quote)
+	}
+
+	return parseUnquotedDotEnvValue(valuePart), start, nil
+}
+
+func parseQuotedDotEnvValue(lines []string, start int, valuePart string, quote byte) (string, int, error) {
+	var b strings.Builder
+	currentLine := start
+	segment := valuePart[1:]
+
+	for {
+		for i := 0; i < len(segment); i++ {
+			ch := segment[i]
+			if quote == '"' && ch == '\\' && i+1 < len(segment) {
+				i++
+				switch segment[i] {
+				case 'n':
+					b.WriteByte('\n')
+				case 'r':
+					b.WriteByte('\r')
+				case 't':
+					b.WriteByte('\t')
+				case '\\', '"', '$':
+					b.WriteByte(segment[i])
+				default:
+					b.WriteByte(segment[i])
+				}
+				continue
+			}
+
+			if ch == quote {
+				return b.String(), currentLine, nil
+			}
+
+			b.WriteByte(ch)
+		}
+
+		if currentLine+1 >= len(lines) {
+			return b.String(), currentLine, nil
+		}
+
+		b.WriteByte('\n')
+		currentLine++
+		segment = lines[currentLine]
+	}
+}
+
+func parseUnquotedDotEnvValue(valuePart string) string {
+	value := valuePart
+	for i := 0; i < len(valuePart); i++ {
+		if valuePart[i] != '#' {
+			continue
+		}
+		if i == 0 {
+			return ""
+		}
+		if valuePart[i-1] == ' ' || valuePart[i-1] == '\t' {
+			return strings.TrimSpace(valuePart[:i])
+		}
+	}
+
+	return value
+}
+
+// MustLoadDotEnv loads a .env file or panics.
+func MustLoadDotEnv(path string) {
+	if err := LoadDotEnv(path); err != nil {
+		panic(err)
+	}
+}