264 lines
11 KiB
Rust
264 lines
11 KiB
Rust
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use proc_macro::TokenStream;
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use quote::quote;
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use std::collections::HashSet;
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use syn::spanned::Spanned;
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pub fn derive_params(input: TokenStream) -> TokenStream {
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let ast = syn::parse_macro_input!(input as syn::DeriveInput);
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let struct_name = &ast.ident;
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let fields = match ast.data {
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syn::Data::Struct(syn::DataStruct {
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fields: syn::Fields::Named(named_fields),
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..
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}) => named_fields,
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_ => {
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return syn::Error::new(
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ast.span(),
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"Deriving Params is only supported on structs with named fields",
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)
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.to_compile_error()
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.into()
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}
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};
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// We only care about fields with `id`, `persist`, and `nested` attributes. For the `id` fields
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// we'll build a mapping function that creates a hashmap containing pointers to those
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// parmaeters. For the `persist` function we'll create functions that serialize and deserialize
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// those fields individually (so they can be added and removed independently of eachother) using
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// JSON. The `nested` fields should also implement the `Params` trait and their fields will be
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// inherited and added to this field's lists.
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let mut param_mapping_insert_tokens = Vec::new();
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let mut param_id_string_tokens = Vec::new();
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let mut field_serialize_tokens = Vec::new();
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let mut field_deserialize_tokens = Vec::new();
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let mut nested_fields_idents = Vec::new();
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// We'll also enforce that there are no duplicate keys at compile time
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// TODO: This doesn't work for nested fields since we don't know anything about the fields on
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// the nested structs
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let mut param_ids = HashSet::new();
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let mut persist_ids = HashSet::new();
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for field in fields.named {
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let field_name = match &field.ident {
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Some(ident) => ident,
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_ => continue,
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};
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// These two attributes are mutually exclusive
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let mut id_attr: Option<String> = None;
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let mut persist_attr: Option<String> = None;
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let mut nested = false;
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for attr in &field.attrs {
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if attr.path.is_ident("id") {
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match attr.parse_meta() {
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Ok(syn::Meta::NameValue(syn::MetaNameValue {
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lit: syn::Lit::Str(s),
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..
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})) => {
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if id_attr.is_none() {
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id_attr = Some(s.value());
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} else {
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return syn::Error::new(attr.span(), "Duplicate id attribute")
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.to_compile_error()
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.into();
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}
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}
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_ => {
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return syn::Error::new(
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attr.span(),
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"The id attribute should be a key-value pair with a string argument: #[id = \"foo_bar\"]",
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)
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.to_compile_error()
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.into()
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}
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};
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} else if attr.path.is_ident("persist") {
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match attr.parse_meta() {
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Ok(syn::Meta::NameValue(syn::MetaNameValue {
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lit: syn::Lit::Str(s),
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..
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})) => {
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if persist_attr.is_none() {
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persist_attr = Some(s.value());
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} else {
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return syn::Error::new(attr.span(), "Duplicate persist attribute")
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.to_compile_error()
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.into();
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}
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}
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_ => {
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return syn::Error::new(
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attr.span(),
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"The persist attribute should be a key-value pair with a string argument: #[persist = \"foo_bar\"]",
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)
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.to_compile_error()
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.into()
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}
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};
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} else if attr.path.is_ident("nested") {
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match attr.parse_meta() {
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Ok(syn::Meta::Path(_)) => {
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if !nested {
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nested = true;
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} else {
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return syn::Error::new(attr.span(), "Duplicate nested attribute")
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.to_compile_error()
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.into();
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}
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}
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_ => {
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return syn::Error::new(
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attr.span(),
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"The nested attribute should not have any arguments: #[nested]",
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)
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.to_compile_error()
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.into();
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}
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};
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}
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}
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match (id_attr, persist_attr) {
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(Some(param_id), None) => {
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if !param_ids.insert(param_id.clone()) {
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return syn::Error::new(
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field.span(),
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"Multiple fields with the same parameter ID found",
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)
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.to_compile_error()
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.into();
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}
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// The specific parameter types know how to convert themselves into the correct ParamPtr
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// variant
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param_mapping_insert_tokens
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.push(quote! { param_map.insert(#param_id, self.#field_name.as_ptr()); });
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param_id_string_tokens.push(quote! { #param_id, });
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}
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(None, Some(stable_name)) => {
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if !persist_ids.insert(stable_name.clone()) {
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return syn::Error::new(
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field.span(),
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"Multiple persisted fields with the same ID found",
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)
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.to_compile_error()
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.into();
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}
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// We don't know anything about the field types, but because we can generate this
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// function we get type erasure for free since we only need to worry about byte
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// vectors
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field_serialize_tokens.push(quote! {
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match ::nih_plug::param::internals::PersistentField::map(
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&self.#field_name,
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::nih_plug::param::internals::serialize_field,
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) {
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Ok(data) => {
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serialized.insert(String::from(#stable_name), data);
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}
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Err(err) => {
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::nih_plug::nih_log!("Could not serialize '{}': {}", #stable_name, err)
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}
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};
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});
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field_deserialize_tokens.push(quote! {
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#stable_name => {
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match ::nih_plug::param::internals::deserialize_field(&data) {
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Ok(deserialized) => {
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::nih_plug::param::internals::PersistentField::set(
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&self.#field_name,
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deserialized,
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);
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}
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Err(err) => {
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::nih_plug::nih_log!(
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"Could not deserialize '{}': {}",
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#stable_name,
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err
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)
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}
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};
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}
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});
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}
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(Some(_), Some(_)) => {
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return syn::Error::new(
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field.span(),
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"The id and persist attributes are mutually exclusive",
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)
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.to_compile_error()
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.into();
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}
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(None, None) => (),
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}
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if nested {
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nested_fields_idents.push(field_name.clone());
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}
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}
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quote! {
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impl Params for #struct_name {
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fn param_map(
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self: std::pin::Pin<&Self>,
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) -> std::collections::HashMap<&'static str, nih_plug::param::internals::ParamPtr> {
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// This may not be in scope otherwise
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use ::nih_plug::param::Param;
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let mut param_map = std::collections::HashMap::new();
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#(#param_mapping_insert_tokens)*
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let nested_fields: &[&dyn Params] = &[#(&self.#nested_fields_idents),*];
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for nested_params in nested_fields {
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unsafe { param_map.extend(Pin::new_unchecked(*nested_params).param_map()) };
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}
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param_map
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}
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fn param_ids(self: std::pin::Pin<&Self>) -> Vec<&'static str> {
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let mut ids = vec![#(#param_id_string_tokens)*];
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let nested_fields: &[&dyn Params] = &[#(&self.#nested_fields_idents),*];
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for nested_params in nested_fields {
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unsafe { ids.append(&mut Pin::new_unchecked(*nested_params).param_ids()) };
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}
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ids
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}
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fn serialize_fields(&self) -> ::std::collections::HashMap<String, String> {
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let mut serialized = ::std::collections::HashMap::new();
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#(#field_serialize_tokens)*
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let nested_fields: &[&dyn Params] = &[#(&self.#nested_fields_idents),*];
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for nested_params in nested_fields {
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unsafe { serialized.extend(Pin::new_unchecked(*nested_params).serialize_fields()) };
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}
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serialized
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}
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fn deserialize_fields(&self, serialized: &::std::collections::HashMap<String, String>) {
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for (field_name, data) in serialized {
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match field_name.as_str() {
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#(#field_deserialize_tokens)*
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_ => ::nih_plug::nih_log!("Unknown serialized field name: {} (this may not be accurate)", field_name),
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}
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}
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// FIXME: The above warning will course give false postiives when using nested
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// parameter structs. An easy fix would be to use
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// https://doc.rust-lang.org/std/collections/struct.HashMap.html#method.drain_filter
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// once that gets stabilized.
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let nested_fields: &[&dyn Params] = &[#(&self.#nested_fields_idents),*];
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for nested_params in nested_fields {
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unsafe { Pin::new_unchecked(*nested_params).deserialize_fields(serialized) };
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}
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}
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}
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}
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.into()
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}
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