Merge pull request #599 from lilizoey/refactor/rewrite-convert-derives

Rewrite the derive macros related to `GodotConvert`

Author: Bromeon

godot-macros/src/derive/data_models/c_style_enum.rs

@@ -0,0 +1,150 @@
+/*
+ * Copyright (c) godot-rust; Bromeon and contributors.
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+use proc_macro2::{Ident, Literal, Span, TokenTree};
+
+use crate::util::{bail, error};
+use crate::ParseResult;
+
+/// Stores info from c-style enums for use in deriving `GodotConvert` and other related traits.
+#[derive(Clone, Debug)]
+pub struct CStyleEnum {
+    /// The names of each variant.
+    enumerator_names: Vec<Ident>,
+    /// The discriminants of each variant, both explicit and implicit.
+    enumerator_ords: Vec<Literal>,
+}
+
+impl CStyleEnum {
+    /// Parses the enum.
+    ///
+    /// Ensures all the variants are unit variants, and that any explicit discriminants are integer literals.
+    pub fn parse_enum(enum_: &venial::Enum) -> ParseResult<Self> {
+        let variants = enum_
+            .variants
+            .items()
+            .map(CStyleEnumerator::parse_enum_variant)
+            .collect::<ParseResult<Vec<_>>>()?;
+
+        let (names, discriminants) = Self::create_discriminant_mapping(variants)?;
+
+        Ok(Self {
+            enumerator_names: names,
+            enumerator_ords: discriminants,
+        })
+    }
+
+    fn create_discriminant_mapping(
+        enumerators: Vec<CStyleEnumerator>,
+    ) -> ParseResult<(Vec<Ident>, Vec<Literal>)> {
+        // See here for how implicit discriminants are decided
+        // https://doc.rust-lang.org/reference/items/enumerations.html#implicit-discriminants
+        let mut names = Vec::new();
+        let mut discriminants = Vec::new();
+
+        let mut last_discriminant = None;
+        for enumerator in enumerators.into_iter() {
+            let discriminant_span = enumerator.discriminant_span();
+
+            let discriminant = match enumerator.discriminant_as_i64()? {
+                Some(discriminant) => discriminant,
+                None => last_discriminant.unwrap_or(0) + 1,
+            };
+            last_discriminant = Some(discriminant);
+
+            let mut discriminant = Literal::i64_unsuffixed(discriminant);
+            discriminant.set_span(discriminant_span);
+
+            names.push(enumerator.name);
+            discriminants.push(discriminant)
+        }
+
+        Ok((names, discriminants))
+    }
+
+    /// Returns the names of the variants, in order of the variants.
+    pub fn names(&self) -> &[Ident] {
+        &self.enumerator_names
+    }
+
+    /// Returns the discriminants of each variant, in order of the variants.
+    pub fn discriminants(&self) -> &[Literal] {
+        &self.enumerator_ords
+    }
+
+    /// Return a hint string for use with `PropertyHint::ENUM` where each variant has an explicit integer hint.
+    pub fn to_int_hint(&self) -> String {
+        self.enumerator_names
+            .iter()
+            .zip(self.enumerator_ords.iter())
+            .map(|(name, discrim)| format!("{name}:{discrim}"))
+            .collect::<Vec<_>>()
+            .join(",")
+    }
+
+    /// Return a hint string for use with `PropertyHint::ENUM` where the variants are just kept as strings.
+    pub fn to_string_hint(&self) -> String {
+        self.enumerator_names
+            .iter()
+            .map(ToString::to_string)
+            .collect::<Vec<_>>()
+            .join(",")
+    }
+}
+
+/// Each variant in a c-style enum.
+#[derive(Clone, Debug)]
+pub struct CStyleEnumerator {
+    /// The name of the variant.
+    name: Ident,
+    /// The explicit discriminant of the variant, `None` means there was no explicit discriminant.
+    discriminant: Option<TokenTree>,
+}
+
+impl CStyleEnumerator {
+    /// Parse an enum variant, erroring if it isn't a unit variant.
+    fn parse_enum_variant(enum_variant: &venial::EnumVariant) -> ParseResult<Self> {
+        match enum_variant.contents {
+            venial::StructFields::Unit => {}
+            _ => {
+                return bail!(
+                    &enum_variant.contents,
+                    "GodotConvert only supports c-style enums"
+                )
+            }
+        }
+
+        Ok(Self {
+            name: enum_variant.name.clone(),
+            discriminant: enum_variant.value.as_ref().map(|val| &val.value).cloned(),
+        })
+    }
+
+    /// Returns the discriminant parsed as an i64 literal.
+    fn discriminant_as_i64(&self) -> ParseResult<Option<i64>> {
+        let Some(discriminant) = self.discriminant.as_ref() else {
+            return Ok(None);
+        };
+
+        let int = discriminant
+            .to_string()
+            .parse::<i64>()
+            .map_err(|_| error!(discriminant, "expected i64 literal"))?;
+
+        Ok(Some(int))
+    }
+
+    /// Returns a span suitable for the discriminant of the variant.
+    ///
+    /// If there was no explicit discriminant, this will use the span of the name instead.
+    fn discriminant_span(&self) -> Span {
+        match &self.discriminant {
+            Some(discriminant) => discriminant.span(),
+            None => self.name.span(),
+        }
+    }
+}

godot-macros/src/derive/data_models/godot_attribute.rs

@@ -0,0 +1,90 @@
+/*
+ * Copyright (c) godot-rust; Bromeon and contributors.
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+use proc_macro2::{Ident, Span, TokenStream};
+use quote::ToTokens;
+use venial::Declaration;
+
+use crate::util::{bail, KvParser};
+use crate::ParseResult;
+
+/// Stores data related to the `#[godot(..)]` attribute.
+pub enum GodotAttribute {
+    /// `#[godot(transparent)]`
+    Transparent { span: Span },
+    /// `#[godot(via = via_type)]`
+    Via { span: Span, via_type: ViaType },
+}
+
+impl GodotAttribute {
+    pub fn parse_attribute(declaration: &Declaration) -> ParseResult<Self> {
+        let mut parser = KvParser::parse_required(declaration.attributes(), "godot", declaration)?;
+        let attribute = Self::parse(&mut parser)?;
+        parser.finish()?;
+
+        Ok(attribute)
+    }
+
+    fn parse(parser: &mut KvParser) -> ParseResult<Self> {
+        let span = parser.span();
+
+        if parser.handle_alone("transparent")? {
+            return Ok(Self::Transparent { span });
+        }
+
+        if let Some(via_type) = parser.handle_ident("via")? {
+            return Ok(Self::Via {
+                span,
+                via_type: ViaType::parse_ident(via_type)?,
+            });
+        }
+
+        bail!(
+            span,
+            "expected either `#[godot(transparent)]` or `#[godot(via = <via_type>)]`"
+        )
+    }
+
+    /// The span of the entire attribute.
+    ///
+    /// Specifically this is the span of the `[ ]` group from a `#[godot(...)]` attribute.
+    pub fn span(&self) -> Span {
+        match self {
+            GodotAttribute::Transparent { span } => *span,
+            GodotAttribute::Via { span, .. } => *span,
+        }
+    }
+}
+
+/// The via type from a `#[godot(via = via_type)]` attribute.
+pub enum ViaType {
+    /// The via type is `GString`
+    GString { gstring_ident: Ident },
+    /// The via type is an integer
+    Int { int_ident: Ident },
+}
+
+impl ViaType {
+    fn parse_ident(ident: Ident) -> ParseResult<Self> {
+        let via_type = match ident.to_string().as_str() {
+            "GString" => ViaType::GString { gstring_ident: ident },
+            "i8" |"i16" | "i32" | "i64" | "u8" | "u16" | "u32" => ViaType::Int { int_ident: ident },
+            other => return bail!(ident, "Via type `{other}` is not supported, expected one of: GString, i8, i16, i32, i64, u8, u16, u32")
+        };
+
+        Ok(via_type)
+    }
+}
+
+impl ToTokens for ViaType {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        match self {
+            ViaType::GString { gstring_ident } => gstring_ident.to_tokens(tokens),
+            ViaType::Int { int_ident } => int_ident.to_tokens(tokens),
+        }
+    }
+}

godot-macros/src/derive/data_models/godot_convert.rs

@@ -0,0 +1,117 @@
+/*
+ * Copyright (c) godot-rust; Bromeon and contributors.
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+use proc_macro2::{Ident, TokenStream};
+use quote::ToTokens;
+use venial::Declaration;
+
+use crate::util::bail;
+use crate::ParseResult;
+
+use super::c_style_enum::CStyleEnum;
+use super::godot_attribute::{GodotAttribute, ViaType};
+use super::newtype::NewtypeStruct;
+
+/// Stores all relevant data to derive `GodotConvert` and other related traits.
+pub struct GodotConvert {
+    /// The name of the type we're deriving for.
+    pub ty_name: Ident,
+    /// The data from the type and `godot` attribute.
+    pub convert_type: ConvertType,
+}
+
+impl GodotConvert {
+    pub fn parse_declaration(declaration: Declaration) -> ParseResult<Self> {
+        let (name, where_clause, generic_params) = match &declaration {
+            venial::Declaration::Struct(struct_) => (
+                struct_.name.clone(),
+                &struct_.where_clause,
+                &struct_.generic_params,
+            ),
+            venial::Declaration::Enum(enum_) => (
+                enum_.name.clone(),
+                &enum_.where_clause,
+                &enum_.generic_params,
+            ),
+            other => {
+                return bail!(
+                    other,
+                    "`GodotConvert` only supports structs and enums currently"
+                )
+            }
+        };
+
+        if let Some(where_clause) = where_clause {
+            return bail!(
+                where_clause,
+                "`GodotConvert` does not support where clauses"
+            );
+        }
+
+        if let Some(generic_params) = generic_params {
+            return bail!(generic_params, "`GodotConvert` does not support generics");
+        }
+
+        let data = ConvertType::parse_declaration(declaration)?;
+
+        Ok(Self {
+            ty_name: name,
+            convert_type: data,
+        })
+    }
+}
+
+/// Stores what kind of `GodotConvert` derive we're doing.
+pub enum ConvertType {
+    /// Deriving for a newtype struct.
+    NewType { field: NewtypeStruct },
+    /// Deriving for an enum.
+    Enum { variants: CStyleEnum, via: ViaType },
+}
+
+impl ConvertType {
+    pub fn parse_declaration(declaration: Declaration) -> ParseResult<Self> {
+        let attribute = GodotAttribute::parse_attribute(&declaration)?;
+
+        match &declaration {
+            Declaration::Struct(struct_) => {
+                let GodotAttribute::Transparent { .. } = attribute else {
+                    return bail!(attribute.span(), "`GodotConvert` on structs only works with `#[godot(transparent)]` currently");
+                };
+
+                Ok(Self::NewType {
+                    field: NewtypeStruct::parse_struct(struct_)?,
+                })
+            }
+            Declaration::Enum(enum_) => {
+                let GodotAttribute::Via { via_type, .. } = attribute else {
+                    return bail!(
+                        attribute.span(),
+                        "`GodotConvert` on enums requires `#[godot(via = ...)]` currently"
+                    );
+                };
+
+                Ok(Self::Enum {
+                    variants: CStyleEnum::parse_enum(enum_)?,
+                    via: via_type,
+                })
+            }
+            _ => bail!(
+                declaration,
+                "`GodotConvert` only supports structs and enums currently"
+            ),
+        }
+    }
+
+    /// Returns the type for use in `type Via = <type>;` in `GodotConvert` implementations.
+    pub fn via_type(&self) -> TokenStream {
+        match self {
+            ConvertType::NewType { field } => field.ty.to_token_stream(),
+            ConvertType::Enum { via, .. } => via.to_token_stream(),
+        }
+    }
+}

godot-macros/src/derive/data_models/mod.rs

@@ -0,0 +1,16 @@
+/*
+ * Copyright (c) godot-rust; Bromeon and contributors.
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+mod c_style_enum;
+mod godot_attribute;
+mod godot_convert;
+mod newtype;
+
+pub use c_style_enum::*;
+pub use godot_attribute::*;
+pub use godot_convert::*;
+pub use newtype::*;