Support marking classes as interfaces (#155)

* Support marking classes as interfaces

This allows passing flags as part of `#[php_class(flags=Interface]` etc, which allows one to mark a class as being an interface.

When a class is an interface, it also shouldn't get a constructor created for it.

* rustfmt

crates/macros/src/class.rs

@@ -22,6 +22,7 @@ pub struct Class {
     /// A function name called when creating the class entry. Given an instance
     /// of `ClassBuilder` and must return it.
     pub modifier: Option<String>,
+    pub flags: Option<String>,
 }
 
 #[derive(Debug)]
@@ -37,6 +38,7 @@ pub enum ParsedAttribute {
 pub struct AttrArgs {
     name: Option<String>,
     modifier: Option<String>,
+    flags: Option<Expr>,
 }
 
 pub fn parser(args: AttributeArgs, mut input: ItemStruct) -> Result<TokenStream> {
@@ -117,6 +119,7 @@ pub fn parser(args: AttributeArgs, mut input: ItemStruct) -> Result<TokenStream>
     let ItemStruct { ident, .. } = &input;
     let class_name = args.name.unwrap_or_else(|| ident.to_string());
     let struct_path = ident.to_string();
+    let flags = args.flags.map(|flags| flags.to_token_stream().to_string());
     let class = Class {
         class_name,
         struct_path,
@@ -125,6 +128,7 @@ pub fn parser(args: AttributeArgs, mut input: ItemStruct) -> Result<TokenStream>
         docs: comments,
         properties,
         modifier: args.modifier,
+        flags,
         ..Default::default()
     };
 

crates/macros/src/startup_function.rs

@@ -121,6 +121,31 @@ fn build_classes(classes: &HashMap<String, Class>) -> Result<Vec<TokenStream>> {
                 }
             });
 
+            let flags = {
+                if let Some(flags) = &class.flags {
+                    let mut name = "::ext_php_rs::flags::ClassFlags::".to_owned();
+                    name.push_str(flags);
+                    let expr: Expr = syn::parse_str(&name).map_err(|_| {
+                        anyhow!("Invalid expression given for `{}` flags", class_name)
+                    })?;
+                    Some(quote! { .flags(#expr) })
+                } else {
+                    None
+                }
+            };
+
+            let object_override = {
+                if let Some(flags) = &class.flags {
+                    if  flags == "Interface" {
+                        None
+                    } else {
+                        Some(quote! { .object_override::<#ident>() })
+                    }
+                } else {
+                    Some(quote! { .object_override::<#ident>() })
+                }
+            };
+
             Ok(quote! {{
                 let builder = ::ext_php_rs::builders::ClassBuilder::new(#class_name)
                     #(#methods)*
@@ -128,7 +153,9 @@ fn build_classes(classes: &HashMap<String, Class>) -> Result<Vec<TokenStream>> {
                     #(#interfaces)*
                     // #(#properties)*
                     #parent
-                    .object_override::<#ident>();
+                    #flags
+                    #object_override
+                    ;
                 #class_modifier
                 let class = builder.build()
                     .expect(concat!("Unable to build class `", #class_name, "`"));