Adding support for a tree(skip) field attribute

CHANGELOG.md

@@ -22,6 +22,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 
 * Deserializing with borrowed data is now supported.
+* [derive] Added `#[tree(skip)]` macro attribute to allow skipping entries.
 
 ## [0.8.0](https://github.com/quartiq/miniconf/compare/v0.7.1...v0.8.0) - 2023-08-03
 

README.md

@@ -40,6 +40,10 @@ struct Settings {
     array: [i32; 2],
     option: Option<i32>,
 
+    // Exclude an element (not Deserialize/Serialize)
+    #[tree(skip)]
+    skipped: (),
+
     // Exposing elements of containers
     // ... by field name
     #[tree]

miniconf_derive/src/field.rs

@@ -14,17 +14,13 @@ impl StructField {
         }
         .iter()
         .cloned()
-        .map(Self::new)
+        .filter_map(Self::new)
         .collect()
     }
 
-    pub fn new(field: syn::Field) -> Self {
-        let depth = Self::parse_depth(&field);
-        Self { field, depth }
-    }
-
-    fn parse_depth(field: &syn::Field) -> usize {
+    pub fn new(field: syn::Field) -> Option<Self> {
         let mut depth = 0;
+        let mut skip = false;
 
         for attr in field.attrs.iter() {
             if attr.path().is_ident("tree") {
@@ -39,14 +35,21 @@ impl StructField {
                         let lit: LitInt = content.parse()?;
                         depth = lit.base10_parse()?;
                         Ok(())
+                    } else if meta.path.is_ident("skip") {
+                        skip = true;
+                        Ok(())
                     } else {
                         Err(meta.error(format!("unrecognized miniconf attribute {:?}", meta.path)))
                     }
                 })
                 .unwrap();
             }
         }
-        depth
+        if skip {
+            None
+        } else {
+            Some(Self { field, depth })
+        }
     }
 
     fn walk_type_params<F>(