feat: improve error message

Author: hengfeiyang

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "dotenv_config"
-version = "0.1.9"
+version = "0.2.0"
 edition = "2021"
 authors = ["Hengfei Yang <hengfei.yang@gmail.com>"]
 description = "parse `env` to config struct for Rust"
@@ -20,4 +20,4 @@ askama = "0.12.1"      # Type-safe, compiled Jinja-like templates for Rust
 convert_case = "0.6.0" # Convert a string to snake_case, kebab-case, or camelCase
 
 [dev-dependencies]
-dotenvy = "0.15.6"
+dotenvy = "0.15.7"

rust-toolchain.toml

@@ -1,2 +1,2 @@
 [toolchain]
-channel = "1.75.0"
+channel = "1.82.0"

templates/builder.j2

@@ -25,7 +25,7 @@ impl {{ name }} {
         help_map
     }
 
-    pub fn init() -> Result<{{ name }}, &'static str> {
+    pub fn init() -> Result<{{ name }}, String> {
         let mut key: &str;
         {% for field in fields %}
         {% if field.attr_name.is_empty() %}
@@ -37,7 +37,7 @@ impl {{ name }} {
         let {{ field.name }}: Option<{{ field.typ }}> = match std::env::var(key) {
             Ok(val) => match val.to_lowercase().parse() {
                 Ok(v) => Some(v),
-                Err(_) => Some("".parse().unwrap()),
+                Err(_) => {return Err(format!("{}: except a value of [{{ field.typ }}]", key));},
             },
             Err(err) => {
                 {% if field.attr_default.is_empty() %}
@@ -60,7 +60,10 @@ impl {{ name }} {
         };
         {% else if field.attr_parse %}
         let {{ field.name }}: Option<{{ field.typ }}> = match std::env::var(key) {
-            Ok(val) => val.parse::<{{ field.typ }}>().ok(),
+            Ok(val) => match val.parse::<{{ field.typ }}>() {
+                Ok(v) => Some(v),
+                Err(_) => {return Err(format!("{}: except a value of [{{ field.typ }}]", key));},
+            },
             Err(_) => {
                 {% if field.attr_default.is_empty() %}
                 Default::default().parse::<{{ field.typ }}>().ok()