pywr_v1_schema_macros/lib.rs
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use proc_macro::TokenStream;
use quote::quote;
/// A derive macro for Pywr nodes that implements `parameters` and `parameters_mut` methods.
#[proc_macro_derive(PywrNode)]
pub fn pywr_node_macro(input: TokenStream) -> TokenStream {
// Parse the input tokens into a syntax tree
let input = syn::parse_macro_input!(input as syn::DeriveInput);
impl_parameter_references_derive(&input)
}
/// A derive macro for Pywr parameters that implements `parameters`, `parameters_mut`,
/// `resource_paths` and `update_resource_paths` methods.
#[proc_macro_derive(PywrParameter)]
pub fn pywr_parameter_macro(input: TokenStream) -> TokenStream {
// Parse the input tokens into a syntax tree
let input = syn::parse_macro_input!(input as syn::DeriveInput);
let mut expanded = impl_parameter_references_derive(&input);
expanded.extend(impl_parameter_resource_paths_derive(&input));
expanded
}
/// Generates a [`TokenStream`] containing the implementation of two methods, `parameters`
/// and `parameters_mut`, for the given struct.
///
/// The `parameters` method returns a [`HashMap`] of parameter names to [`ParameterValueType`],
/// and the `parameters_mut` method returns a [`HashMap`] of parameter names to [`ParameterValueTypeMut`].
/// This is intended to be used for nodes and parameter structs in the Pywr schema.
///
/// Currently the implementation is limited to simple type definitions such as `Option<ParameterValue>` or `ParameterValue`.
fn impl_parameter_references_derive(ast: &syn::DeriveInput) -> TokenStream {
// Name of the node type
let name = &ast.ident;
if let syn::Data::Struct(data) = &ast.data {
// Only apply this to structs
// Help struct for capturing parameter fields and whether they are optional.
struct ParamField {
field_name: syn::Ident,
optional: bool,
}
// Iterate through all fields of the struct. Try to find fields that reference
// parameters (e.g. `Option<ParameterValue>` or `ParameterValue`).
let parameter_fields: Vec<ParamField> = data
.fields
.iter()
.filter_map(|field| {
let field_ident = field.ident.as_ref()?;
// Identify optional fields
match type_to_ident(&field.ty) {
Some(PywrField::Optional(ident)) => {
// If optional and a parameter identifier then add to the list
is_parameter_ident(&ident).then_some(ParamField {
field_name: field_ident.clone(),
optional: true,
})
}
Some(PywrField::Required(ident)) => {
// Otherwise, if a parameter identifier then add to the list
is_parameter_ident(&ident).then_some(ParamField {
field_name: field_ident.clone(),
optional: false,
})
}
None => None, // All other fields are ignored.
}
})
.collect();
// Insert statements for non-mutable version
let inserts = parameter_fields
.iter()
.map(|param_field| {
let ident = ¶m_field.field_name;
let key = ident.to_string();
if param_field.optional {
quote! {
if let Some(p) = &self.#ident {
attributes.insert(#key, p.into());
}
}
} else {
quote! {
let #ident = &self.#ident;
attributes.insert(#key, #ident.into());
}
}
})
.collect::<Vec<_>>();
// Insert statements for mutable version
let inserts_mut = parameter_fields
.iter()
.map(|param_field| {
let ident = ¶m_field.field_name;
let key = ident.to_string();
if param_field.optional {
quote! {
if let Some(p) = &mut self.#ident {
attributes.insert(#key, p.into());
}
}
} else {
quote! {
let #ident = &mut self.#ident;
attributes.insert(#key, #ident.into());
}
}
})
.collect::<Vec<_>>();
// Create the two parameter methods using the insert statements
let expanded = quote! {
impl #name {
pub fn parameters(&self) -> HashMap<&str, ParameterValueType> {
let mut attributes = HashMap::new();
#(
#inserts
)*
attributes
}
pub fn parameters_mut(&mut self) -> HashMap<&str, ParameterValueTypeMut> {
let mut attributes = HashMap::new();
#(
#inserts_mut
)*
attributes
}
}
};
// Hand the output tokens back to the compiler.
TokenStream::from(expanded)
} else {
panic!("Only structs are supported for #[derive(PywrNode)] or #[derive(PywrParameter)]")
}
}
/// Generates a [`TokenStream`] containing the implementation `resource_paths`
/// and `update_resource_paths` methods.
fn impl_parameter_resource_paths_derive(ast: &syn::DeriveInput) -> TokenStream {
// Name of the node type
let name = &ast.ident;
if let syn::Data::Struct(data) = &ast.data {
// Helper struct to capture PathBuf fields
struct PathField {
field_name: syn::Ident,
ty: PathFieldType,
optional: bool,
}
let path_fields: Vec<PathField> = data
.fields
.iter()
.filter_map(|field| {
let field_ident = field.ident.as_ref()?;
// Identify optional fields
match type_to_ident(&field.ty) {
Some(PywrField::Optional(ident)) => {
// If optional and a path identifier then add to the list
ident_to_path_type(&ident).map(|field_type| PathField {
field_name: field_ident.clone(),
ty: field_type,
optional: true,
})
}
Some(PywrField::Required(ident)) => {
// If required, and a path identifier then add to the list
ident_to_path_type(&ident).map(|field_type| PathField {
field_name: field_ident.clone(),
ty: field_type,
optional: false,
})
}
None => None, // All other field types are ignored
}
})
.collect();
// Insert statements for non-mutable version
let inserts = path_fields
.iter()
.map(|param_field| {
let ident = ¶m_field.field_name;
match ¶m_field.ty {
PathFieldType::ExternalDataRef => {
if param_field.optional {
quote! {
if let Some(external) = &self.#ident {
resource_paths.push(external.url.clone());
}
}
} else {
quote! {
resource_paths.push(self.#ident.url.clone());
}
}
}
PathFieldType::PathBuf => {
if param_field.optional {
quote! {
if let Some(p) = &self.#ident {
resource_paths.push(p.clone());
}
}
} else {
quote! {
resource_paths.push(self.#ident.clone());
}
}
}
}
})
.collect::<Vec<_>>();
// Update statements for the `update_resource_paths` method
let updates = path_fields
.iter()
.map(|param_field| {
let ident = ¶m_field.field_name;
match ¶m_field.ty {
PathFieldType::ExternalDataRef => {
if param_field.optional {
quote! {
if let Some(external) = &mut self.#ident {
if let Some(new_path) = new_paths.get(&external.url) {
external.url = new_path.clone();
}
}
}
} else {
quote! {
if let Some(new_path) = new_paths.get(&self.#ident.url) {
self.#ident.url = new_path.clone();
}
}
}
}
PathFieldType::PathBuf => {
if param_field.optional {
quote! {
if let Some(path) = &mut self.#ident {
if let Some(new_path) = new_paths.get(path) {
*path = new_path.clone();
}
}
}
} else {
quote! {
if let Some(new_path) = new_paths.get(&self.#ident) {
self.#ident = new_path.clone();
}
}
}
}
}
})
.collect::<Vec<_>>();
// Create the two parameter methods using the insert statements
let expanded = quote! {
impl #name {
pub fn resource_paths(&self) -> Vec<PathBuf> {
let mut resource_paths = Vec::new();
#(
#inserts
)*
resource_paths
}
pub fn update_resource_paths(&mut self, new_paths: &HashMap<PathBuf, PathBuf>) {
#(
#updates
)*
}
}
};
// Hand the output tokens back to the compiler.
TokenStream::from(expanded)
} else {
panic!("Only structs are supported for #[derive(PywrNode)] or #[derive(PywrParameter)]")
}
}
enum PywrField {
Optional(syn::Ident),
Required(syn::Ident),
}
/// Returns the last segment of a type path as an identifier
fn type_to_ident(ty: &syn::Type) -> Option<PywrField> {
match ty {
// Match type's that are a path and not a self type.
syn::Type::Path(type_path) if type_path.qself.is_none() => {
// Match on the last segment
match type_path.path.segments.last() {
Some(last_segment) => {
let ident = &last_segment.ident;
if ident == "Option" {
// The last segment is an Option, now we need to parse the argument
// I.e. the bit in inside the angle brackets.
let first_arg = match &last_segment.arguments {
syn::PathArguments::AngleBracketed(params) => params.args.first(),
_ => None,
};
// Find type arguments; ignore others
let arg_ty = match first_arg {
Some(syn::GenericArgument::Type(ty)) => Some(ty),
_ => None,
};
// Match on path types that are no self types.
let arg_type_path = match arg_ty {
Some(ty) => match ty {
syn::Type::Path(type_path) if type_path.qself.is_none() => {
Some(type_path)
}
_ => None,
},
None => None,
};
// Get the last segment of the path
let last_segment = match arg_type_path {
Some(type_path) => type_path.path.segments.last(),
None => None,
};
// Finally, if there's a last segment return this as an optional `PywrField`
match last_segment {
Some(last_segment) => {
let ident = &last_segment.ident;
Some(PywrField::Optional(ident.clone()))
}
None => None,
}
} else {
// Otherwise, assume this a simple required field
Some(PywrField::Required(ident.clone()))
}
}
None => None,
}
}
_ => None,
}
}
fn is_parameter_ident(ident: &syn::Ident) -> bool {
(ident == "ParameterValue") || (ident == "ParameterValues")
}
enum PathFieldType {
ExternalDataRef,
PathBuf,
}
fn ident_to_path_type(ident: &syn::Ident) -> Option<PathFieldType> {
if ident == "ExternalDataRef" {
Some(PathFieldType::ExternalDataRef)
} else if ident == "PathBuf" {
Some(PathFieldType::PathBuf)
} else {
None
}
}