fix: warn on malformed .env lines instead of silently skipping them

internal/config/dotenv.go

@@ -1,6 +1,8 @@
 package config
 
 import (
+	"bufio"
+	"log"
 	"os"
 	"path/filepath"
 	"strings"
@@ -18,13 +20,13 @@ func LoadDotenv() {
 		parts := strings.Split(v, ",")
 		for i := range parts {
 			parts[i] = strings.TrimSpace(parts[i])
+			loadEnvFile(parts[i])
 		}
-		_ = godotenv.Load(parts...)
 		return
 	}
 
 	// Default: try a few common locations, so starting the process from repo root or backend/ works.
-	// We keep it silent and best-effort.
+	// We keep it silent and best-effort for missing files, but warn on malformed content.
 	candidates := []string{".env"}
 
 	if wd, err := os.Getwd(); err == nil {
@@ -40,12 +42,61 @@ func LoadDotenv() {
 			continue
 		}
 		if _, err := os.Stat(p); err == nil {
-			_ = godotenv.Load(p)
+			loadEnvFile(p)
 			return
 		}
 	}
 }
 
+func loadEnvFile(path string) {
+	file, err := os.Open(path)
+	if err != nil {
+		return
+	}
+	defer file.Close()
+
+	scanner := bufio.NewScanner(file)
+	var buf strings.Builder
+	envMap := make(map[string]string)
+
+	for scanner.Scan() {
+		line := scanner.Text()
+
+		if buf.Len() > 0 {
+			buf.WriteString("\n")
+		}
+		buf.WriteString(line)
+
+		current := buf.String()
+
+		// Skip empty lines and pure comments
+		if strings.TrimSpace(current) == "" || strings.HasPrefix(strings.TrimSpace(current), "#") {
+			buf.Reset()
+			continue
+		}
 
+		parsedMap, err := godotenv.Unmarshal(current)
+		if err == nil {
+			for k, v := range parsedMap {
+				if k == "" {
+					log.Printf("WARNING: malformed line in %s (missing '='): %q\n", path, current)
+				} else {
+					envMap[k] = v
+				}
+			}
+			buf.Reset()
+		}
+	}
 
+	if err := scanner.Err(); err != nil {
+		log.Printf("WARNING: error reading %s: %v\n", path, err)
+	} else if buf.Len() > 0 {
+		log.Printf("WARNING: malformed or unterminated line in %s: %q\n", path, buf.String())
+	}
 
+	for k, v := range envMap {
+		if _, exists := os.LookupEnv(k); !exists {
+			os.Setenv(k, v)
+		}
+	}
+}

internal/config/dotenv_test.go

@@ -0,0 +1,146 @@
+package config
+
+import (
+	"bytes"
+	"log"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+func TestLoadDotenv(t *testing.T) {
+	// Create a temporary directory for our .env files
+	tempDir := t.TempDir()
+
+	tests := []struct {
+		name           string
+		envContent     string
+		expectedEnv    map[string]string
+		notExpectedEnv []string
+		expectLogMsg   string
+	}{
+		{
+			name: "Valid file",
+			envContent: `A=1
+B="multi
+line"
+C=3`,
+			expectedEnv: map[string]string{
+				"A": "1",
+				"B": "multi\nline",
+				"C": "3",
+			},
+		},
+		{
+			name: "Missing equals sign",
+			envContent: `A=1
+BAD_LINE
+B=2`,
+			expectedEnv: map[string]string{
+				"A": "1",
+				"B": "2",
+			},
+			expectLogMsg: `WARNING: malformed line in`,
+		},
+		{
+			name: "Unterminated quote",
+			envContent: `A=1
+B="unterminated
+C=3`,
+			expectedEnv: map[string]string{
+				"A": "1",
+			},
+			notExpectedEnv: []string{"B", "C"},
+			expectLogMsg:   `WARNING: malformed or unterminated line in`,
+		},
+		{
+			name: "Duplicate key (last-wins)",
+			envContent: `A=1
+A=2`,
+			expectedEnv: map[string]string{
+				"A": "2",
+			},
+		},
+		{
+			name:       "Empty file",
+			envContent: ``,
+			expectedEnv: map[string]string{},
+		},
+		{
+			name: "Comment-only line",
+			envContent: `# This is a comment
+# Another comment`,
+			expectedEnv: map[string]string{},
+		},
+		{
+			name: "Mixed with comments",
+			envContent: `A=1
+# A comment
+B=2`,
+			expectedEnv: map[string]string{
+				"A": "1",
+				"B": "2",
+			},
+		},
+		{
+			name: "Does not overwrite existing OS env",
+			envContent: `A=1`,
+			// "A" is set to "EXISTING" in test setup
+			expectedEnv: map[string]string{
+				"A": "EXISTING",
+			},
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			// Clear all environment variables for a clean state
+			os.Clearenv()
+
+			if tc.name == "Does not overwrite existing OS env" {
+				os.Setenv("A", "EXISTING")
+			}
+
+			// Write the env content to a file
+			envPath := filepath.Join(tempDir, ".env")
+			if err := os.WriteFile(envPath, []byte(tc.envContent), 0644); err != nil {
+				t.Fatalf("failed to write .env file: %v", err)
+			}
+
+			// Capture log output
+			var logBuf bytes.Buffer
+			log.SetOutput(&logBuf)
+			defer log.SetOutput(os.Stderr)
+
+			// Tell LoadDotenv to use our specific file
+			os.Setenv("ENV_FILE", envPath)
+
+			LoadDotenv()
+
+			logOutput := logBuf.String()
+
+			// Verify expected env variables
+			for k, v := range tc.expectedEnv {
+				actual := os.Getenv(k)
+				if actual != v {
+					t.Errorf("expected env %s=%q, got %q", k, v, actual)
+				}
+			}
+
+			// Verify not expected env variables
+			for _, k := range tc.notExpectedEnv {
+				if val, exists := os.LookupEnv(k); exists {
+					t.Errorf("expected env %s to not be set, but got %q", k, val)
+				}
+			}
+
+			// Verify log messages
+			if tc.expectLogMsg != "" && !strings.Contains(logOutput, tc.expectLogMsg) {
+				t.Errorf("expected log output to contain %q, got: %q", tc.expectLogMsg, logOutput)
+			} else if tc.expectLogMsg == "" && logOutput != "" {
+				t.Errorf("expected no log output, got: %q", logOutput)
+			}
+		})
+	}
+}