fix ability to override values set in env file by interpolation

Signed-off-by: Nicolas De Loof <nicolas.deloof@gmail.com>

Author: ndeloof

dotenv/env.go

@@ -56,7 +56,7 @@ func GetEnvFromFile(currentEnv map[string]string, filenames []string) (map[strin
 			return envMap, err
 		}
 
-		env, err := ParseWithLookup(bytes.NewReader(b), func(k string) (string, bool) {
+		err = parseWithLookup(bytes.NewReader(b), envMap, func(k string) (string, bool) {
 			v, ok := currentEnv[k]
 			if ok {
 				return v, true
@@ -67,9 +67,6 @@ func GetEnvFromFile(currentEnv map[string]string, filenames []string) (map[strin
 		if err != nil {
 			return envMap, fmt.Errorf("failed to read %s: %w", dotEnvFile, err)
 		}
-		for k, v := range env {
-			envMap[k] = v
-		}
 	}
 
 	return envMap, nil

dotenv/godotenv_test.go

@@ -741,3 +741,36 @@ func TestLoadWithFormat(t *testing.T) {
 	assert.NilError(t, err)
 	assert.DeepEqual(t, expectedValues, env)
 }
+
+func TestMultipleFiles(t *testing.T) {
+	base, err := os.CreateTemp(t.TempDir(), "base.env")
+	assert.NilError(t, err)
+	err = os.WriteFile(base.Name(), []byte(`
+ENV_HOSTNAME=localhost
+ENV_MY_URL="http://${ENV_HOSTNAME}"
+`), 0o600)
+	assert.NilError(t, err)
+
+	override, err := os.CreateTemp(t.TempDir(), "override.env")
+	assert.NilError(t, err)
+	err = os.WriteFile(override.Name(), []byte(`
+ENV_HOSTNAME=dev.my-company.com
+ENV_MY_URL="http://${ENV_HOSTNAME}"
+`), 0o600)
+	assert.NilError(t, err)
+
+	env, err := GetEnvFromFile(nil, []string{base.Name(), override.Name()})
+	assert.NilError(t, err)
+	assert.DeepEqual(t, env, map[string]string{
+		"ENV_HOSTNAME": "dev.my-company.com",
+		"ENV_MY_URL":   "http://dev.my-company.com",
+	})
+
+	osEnv := map[string]string{"ENV_HOSTNAME": "host.local"}
+	env, err = GetEnvFromFile(osEnv, []string{base.Name(), override.Name()})
+	assert.NilError(t, err)
+	assert.DeepEqual(t, env, map[string]string{
+		"ENV_HOSTNAME": "dev.my-company.com",
+		"ENV_MY_URL":   "http://host.local",
+	})
+}