Fixes #20 Adds support for short-version of boolean flags

Users can now use a more concise syntax for specifying a boolean parameter value within an attribute.

A parameter 'foo' can have a 'true' value specified with the following syntax #[my_attr(foo)]

Author: chuck-flowers

attribution-examples/exhaustive-attr/exhaustive-attr-macros/src/lib.rs

@@ -15,6 +15,7 @@ use syn::Stmt;
 #[derive(AttrArgs)]
 struct AttributeArgs {
     flag: bool,
+    simple_flag: bool,
     string: String,
     integer: i64,
     float: f64,
@@ -37,6 +38,10 @@ fn make_print_lines(attr: AttributeArgs) -> impl IntoIterator<Item = Stmt> {
         value: attr.flag,
         span: proc_macro2::Span::call_site(),
     };
+    let simple_flag_val = LitBool {
+        value: attr.simple_flag,
+        span: proc_macro2::Span::call_site(),
+    };
     let string_val = LitStr::new(&attr.string, Span::call_site());
     let integer_val = LitInt::new(&attr.integer.to_string(), Span::call_site());
     let float_val = LitFloat::new(&attr.float.to_string(), Span::call_site());
@@ -50,6 +55,9 @@ fn make_print_lines(attr: AttributeArgs) -> impl IntoIterator<Item = Stmt> {
         parse_quote! {
             println!("flag = {}", #flag_val);
         },
+        parse_quote! {
+            println!("simple_flag = {}", #simple_flag_val);
+        },
         parse_quote! {
             println!("string = {}", #string_val);
         },

attribution-examples/exhaustive-attr/exhaustive-attr/src/main.rs

@@ -1,6 +1,6 @@
 use exhaustive_attr_macros::exhaustive;
 
-#[exhaustive(flag = true, string = "foo", integer = 1, float = 4.0, array_of_integers = [1, 2, 3])]
+#[exhaustive(flag = true, simple_flag, string = "foo", integer = 1, float = 4.0, array_of_integers = [1, 2, 3])]
 fn main() {
     println!("End of main!");
 }

attribution/src/params.rs

@@ -115,17 +115,20 @@ mod tests {
 
     #[test]
     fn parse() {
-        let attr: Attribute = parse_quote!(#[attr(foo = "fooValue", bar = 1, baz = true)]);
+        let attr: Attribute =
+            parse_quote!(#[attr(string = "fooValue", integer = 1, flag = true, simple_flag)]);
         if let proc_macro2::TokenTree::Group(group) = attr.tokens.into_iter().next().unwrap() {
             let attr_args: Parameters = parse2(group.stream()).unwrap();
-            let foo_val = attr_args.get(&"foo".into());
-            let bar_val = attr_args.get(&"bar".into());
-            let baz_val = attr_args.get(&"baz".into());
+            let string_val = attr_args.get(&"string".into());
+            let integer_val = attr_args.get(&"integer".into());
+            let flag_val = attr_args.get(&"flag".into());
+            let simple_flag_val = attr_args.get(&"simple_flag".into());
             let other_val = attr_args.get(&"other".into());
 
-            assert_eq!(foo_val, Some(&ParamVal::Str("fooValue".to_string())));
-            assert_eq!(bar_val, Some(&ParamVal::Int(1)));
-            assert_eq!(baz_val, Some(&ParamVal::Bool(true)));
+            assert_eq!(string_val, Some(&ParamVal::Str("fooValue".to_string())));
+            assert_eq!(integer_val, Some(&ParamVal::Int(1)));
+            assert_eq!(flag_val, Some(&ParamVal::Bool(true)));
+            assert_eq!(simple_flag_val, Some(&ParamVal::Bool(true)));
             assert_eq!(other_val, None);
         } else {
             panic!("Didn't unwrap appropriately");