component_model_meta 0.17.0

A flexible implementation of the Builder pattern supporting nested builders and collection-specific subcomponent_models. Implementation of its derive macro. Should not be used independently, instead use module::component_model which relies on the module.
Documentation 
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use super :: *;
use macro_tools :: { attr, diag, Result, format_ident };

///
/// Generate `ComponentsAssign` trait implementation for the type, providing `components_assign` function
///
/// Output example can be found in in the root of the module
///
pub fn components_assign(input: proc_macro ::TokenStream) -> Result< proc_macro2 ::TokenStream > 
{
  use convert_case :: { Case, Casing };
  let original_input = input.clone();
  let parsed = syn ::parse :: < syn ::ItemStruct >(input)?;
  let has_debug = attr ::has_debug(parsed.attrs.iter())?;

  // name
  let item_name = &parsed.ident;
  let trait_ident = format_ident! {
  "{}ComponentsAssign",
  item_name
 };
  let method_ident = format_ident! {
  "{}_assign",
  item_name.to_string().to_case( Case ::Snake )
 };

  // fields
  // fields
  let (bounds1, bounds2, component_assigns) : (Vec< _ >, Vec< _ >, Vec< _ >) = parsed
  .fields
  .iter()
  .map(|field| {
   let field_type = &field.ty;
   let bound1 = generate_trait_bounds(field_type);
   let bound2 = generate_impl_bounds(field_type);
   let component_assign = generate_component_assign_call(field);
   (bound1, bound2, component_assign)
 })
  .fold((Vec ::new(), Vec ::new(), Vec ::new()), |(mut bounds1, mut bounds2, mut assigns), (b1, b2, assign)| {
   bounds1.push(b1);
   bounds2.push(b2);
   assigns.push(assign);
   (bounds1, bounds2, assigns)
 });

  let bounds1: Vec< _ > = bounds1.into_iter().collect :: < Result< _ >>()?;
  let bounds2: Vec< _ > = bounds2.into_iter().collect :: < Result< _ >>()?;
  let component_assigns: Vec< _ > = component_assigns.into_iter().collect :: < Result< _ >>()?;

  // code
  let doc = "Interface to assign instance from set of components exposed by a single argument.".to_string();
  let trait_bounds = qt! { #( #bounds1 )* IntoT: Clone };
  let impl_bounds = qt! { #( #bounds2 )* #( #bounds1 )* IntoT: Clone };
  let component_assigns = qt! { #( #component_assigns )* };
  let result = qt! {

  #[ doc = #doc ]
  pub trait #trait_ident< IntoT >
  where
   #trait_bounds,
  {
   fn #method_ident( &mut self, component: IntoT );
 }

  impl< T, IntoT > #trait_ident< IntoT > for T
  where
   #impl_bounds,
  {
   #[ inline( always ) ]
   #[ doc = #doc ]
   fn #method_ident( &mut self, component: IntoT )
   {
  #component_assigns
 }
 }

 };

  if has_debug 
  {
  let about = format!("derive: ComponentsAssign\nstructure: {item_name}");
  diag ::report_print(about, &original_input, &result);
 }

  // if has_debug
  // {
  //   diag ::report_print( "derive: ComponentsAssign", original_input, &result );
  // }

  Ok(result)
}

///
/// Generate trait bounds needed for `components_assign`
///
/// ### Output example
///
/// ```ignore
/// IntoT: Into< i32 >
/// ```
///
#[ allow( clippy ::unnecessary_wraps ) ]
fn generate_trait_bounds(field_type: &syn ::Type) -> Result< proc_macro2 ::TokenStream > 
{
  Ok(qt! {
  IntoT: Into< #field_type >,
 })
}

///
/// Generate impl bounds needed for `components_assign`
///
/// ### Output example
///
/// ```ignore
/// T: component_model ::Assign< i32, IntoT >,
/// ```
///
#[ allow( clippy ::unnecessary_wraps ) ]
fn generate_impl_bounds(field_type: &syn ::Type) -> Result< proc_macro2 ::TokenStream > 
{
  Ok(qt! {
  T: component_model ::Assign< #field_type, IntoT >,
 })
}

///
/// Generate set calls needed by `components_assign`
/// Returns a "unit" of work of `components_assign` function, performing `set` on each field.
///
/// Output example
///
/// ```ignore
/// component_model ::Assign :: < i32, _ > ::assign( self.component.clone() );
/// ```
///
#[ allow( clippy ::unnecessary_wraps ) ]
fn generate_component_assign_call(field: &syn ::Field) -> Result< proc_macro2 ::TokenStream > 
{
  // let field_name = field.ident.as_ref().expect( "Expected the field to have a name" );
  let field_type = &field.ty;
  Ok(qt! {
  component_model ::Assign :: < #field_type, _ > ::assign( self, component.clone() );
 })
}