test: add integration tests

README.md

@@ -15,23 +15,21 @@ Procedural macro to derive configuration from files, with optional merging capab
 filecaster = "0.1"
 ```
 
-Example:
-
 ```rust
 use filecaster::FromFile;
-use serde::{Deserialize, Serialize};
 
-#[derive(Debug, Clone, Default, Deserialize, Serialize, FromFile)]
+#[derive(Debug, Clone, FromFile)]
 pub struct MyConfig {
+    #[from_file(default = "localhost")]
     pub host: String,
-    #[default = "8080"]
+    #[from_file(default = 8080)]
     pub port: u16,
-    #[default = "false"]
+    #[from_file(default = false)]
     pub enabled: bool,
 }
 
 fn main() {
-    // Simulate loading from a file (e.g., JSON, YAML)
+    // Simulate loading from a file (e.g., JSON, YAML, TOML)
     let file_content = r#"
         {
             "host": "localhost"

src/from_file.rs

@@ -1,8 +1,8 @@
 use proc_macro2::TokenStream;
 use quote::{format_ident, quote};
 use syn::{
-    Attribute, Data, DeriveInput, Error, Expr, Fields, FieldsNamed, GenericParam, Generics, Meta,
+    Attribute, Data, DeriveInput, Error, Expr, Fields, FieldsNamed, GenericParam, Generics, Lit,
-    Result, WhereClause, WherePredicate, parse_quote, parse2,
+    Meta, MetaList, Result, WhereClause, WherePredicate, parse_quote, parse2,
 };
 
 const WITH_MERGE: bool = cfg!(feature = "merge");
@@ -155,18 +155,7 @@ fn parse_from_file_default_attr(attrs: &[Attribute]) -> Result<Option<Expr>> {
 
         // Parse the content inside the parentheses of #[from_file(...)]
         return match &attr.meta {
-            Meta::List(meta_list) => {
+            Meta::List(meta_list) => parse_default(meta_list),
-                let mut default_expr = None;
-                meta_list.parse_nested_meta(|meta| {
-                    if meta.path.is_ident("default") {
-                        let value = meta.value()?;
-                        let expr = value.parse::<Expr>()?;
-                        default_expr = Some(expr);
-                    }
-                    Ok(())
-                })?;
-                Ok(default_expr)
-            }
             _ => Err(Error::new_spanned(
                 attr,
                 "Expected #[from_file(default = \"literal\")] or similar",
@@ -176,6 +165,28 @@ fn parse_from_file_default_attr(attrs: &[Attribute]) -> Result<Option<Expr>> {
     Ok(None)
 }
 
+fn parse_default(list: &MetaList) -> Result<Option<Expr>> {
+    let mut default_expr = None;
+    list.parse_nested_meta(|meta| {
+        if meta.path.is_ident("default") {
+            let value = meta.value()?;
+            let expr = value.parse::<Expr>()?;
+
+            if let Expr::Lit(expr_lit) = &expr {
+                if let Lit::Str(lit_str) = &expr_lit.lit {
+                    default_expr = Some(parse_quote! {
+                        #lit_str.to_string()
+                    });
+                    return Ok(());
+                }
+            }
+            default_expr = Some(expr);
+        }
+        Ok(())
+    })?;
+    Ok(default_expr)
+}
+
 #[cfg(test)]
 mod tests {
     use claims::{assert_err, assert_none};
@@ -213,18 +224,6 @@ mod tests {
         assert_err!(extract_named_fields(&input));
     }
 
-    #[test]
-    fn parse_default_attrs_picks_first_default() {
-        let attrs: Vec<Attribute> = vec![
-            parse_quote!(#[foo]),
-            parse_quote!(#[from_file(default = "bar")]),
-            parse_quote!(#[from_file(default = "baz")]),
-        ];
-        let expr = parse_from_file_default_attr(&attrs).unwrap().unwrap();
-        // should pick the first default attribute
-        assert_eq!(expr, parse_quote!("bar"));
-    }
-
     #[test]
     fn parse_default_attrs_none() {
         let attrs: Vec<Attribute> = vec![parse_quote!(#[foo])];
@@ -303,11 +302,16 @@ mod tests {
     fn build_derive_clause_defaults() {
         let derive_ts = build_derive_clause();
         let s = derive_ts.to_string();
-        dbg!(&s);
+        if WITH_MERGE {
+            assert!(s.contains(
+                "derive (Debug , Clone , Default , serde :: Deserialize , serde :: Serialize , merge :: Merge)"
+            ));
+        } else {
             assert!(s.contains(
                 "derive (Debug , Clone , Default , serde :: Deserialize , serde :: Serialize)"
             ));
         }
+    }
 
     #[test]
     fn add_trait_bouds_appends_default() {

tests/from_file.rs

@@ -0,0 +1,111 @@
+use filecaster::FromFile;
+
+#[derive(Debug, Clone, PartialEq, FromFile)]
+struct Simple {
+    x: i32,
+    #[from_file(default = "hello")]
+    y: String,
+}
+
+#[derive(Debug, Clone, PartialEq, FromFile)]
+struct NumericDefault {
+    a: i32,
+    #[from_file(default = 42)]
+    b: i32,
+}
+
+#[test]
+fn test_simple_defaults() {
+    // No file passed -> all fields fall back to defaults
+    let s = Simple::from_file(None);
+    assert_eq!(
+        s,
+        Simple {
+            x: 0,
+            y: "hello".to_string(),
+        }
+    );
+}
+
+#[test]
+fn test_simple_override() {
+    // Manually construct the generated `SimpleFile` and override both fields
+    let file = SimpleFile {
+        x: Some(10),
+        y: Some("world".to_string()),
+    };
+    let s = Simple::from_file(Some(file));
+    assert_eq!(
+        s,
+        Simple {
+            x: 10,
+            y: "world".to_string(),
+        }
+    );
+}
+
+#[test]
+fn test_simple_serde_empty() {
+    // Deserialize from JSON missing both fields -> both None
+    let json = "{}";
+    let file: SimpleFile = serde_json::from_str(json).unwrap();
+    let s = Simple::from_file(Some(file));
+    assert_eq!(s.x, 0);
+    assert_eq!(s.y, "hello".to_string());
+}
+
+#[test]
+fn test_simple_serde_partial() {
+    // Deserialize from JSON with only `x`
+    let json = r#"{"x":5}"#;
+    let file: SimpleFile = serde_json::from_str(json).unwrap();
+    let s = Simple::from_file(Some(file));
+    assert_eq!(s.x, 5);
+    assert_eq!(s.y, "hello".to_string());
+}
+
+#[test]
+fn test_simple_serde_full() {
+    // Deserialize from JSON with both fields
+    let json = r#"{"x":7,"y":"rust"}"#;
+    let file: SimpleFile = serde_json::from_str(json).unwrap();
+    let s = Simple::from_file(Some(file));
+    assert_eq!(s.x, 7);
+    assert_eq!(s.y, "rust".to_string());
+}
+
+#[test]
+fn test_numeric_default() {
+    // No file -> default `b = 42`
+    let n = NumericDefault::from_file(None);
+    assert_eq!(n, NumericDefault { a: 0, b: 42 });
+
+    // Override both
+    let file = NumericDefaultFile {
+        a: Some(7),
+        b: Some(99),
+    };
+    let n2 = NumericDefault::from_file(Some(file));
+    assert_eq!(n2, NumericDefault { a: 7, b: 99 });
+}
+
+#[cfg(feature = "merge")]
+mod merge_tests {
+    use super::*;
+    use merge::Merge;
+
+    #[test]
+    fn test_merge_simple_file() {
+        let mut f1 = SimpleFile {
+            x: Some(1),
+            y: None,
+        };
+        let f2 = SimpleFile {
+            x: None,
+            y: Some("foo".to_string()),
+        };
+        f1.merge(f2);
+        assert_eq!(f1.x, Some(1));
+        assert_eq!(f1.y, Some("foo".to_string()));
+    }
+}