Project restructuring, dedicated traits, TryScribeString derive

Cargo.toml

@@ -1,19 +1,7 @@
-[package]
-name = "enumscribe"
-version = "0.1.0"
-authors = ["Tom Panton <pantonshire@gmail.com>"]
-edition = "2018"
-license = "MIT"
-description = "Procedural macros for converting between enums and strings"
-
-[lib]
-proc-macro = true
-
-[dependencies]
-proc-macro2 = "1.0"
-syn = "1.0"
-quote = "1.0"
-
-[dev-dependencies]
-serde = "1.0"
-serde_json = "1.0"
+[workspace]
+members = [
+    "enumscribe",
+    "enumscribe_derive",
+    "enumscribe_tests",
+    "enumscribe_examples"
+]

enumscribe/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "enumscribe"
+version = "0.1.0"
+authors = ["Tom Panton <pantonshire@gmail.com>"]
+edition = "2018"
+license = "MIT"
+description = "Procedural macros for converting between enums and strings"
+
+[dependencies]
+enumscribe_derive = { path = "../enumscribe_derive" }

enumscribe/src/lib.rs

@@ -0,0 +1,34 @@
+#[macro_use]
+extern crate enumscribe_derive;
+
+use std::borrow::Cow;
+
+pub use enumscribe_derive::*;
+
+//TODO
+pub trait ScribeStaticStr {
+    fn scribe(&self) -> &'static str;
+}
+
+//TODO
+pub trait TryScribeStaticStr {
+    fn try_scribe(&self) -> Option<&'static str>;
+}
+
+pub trait ScribeString {
+    fn scribe(&self) -> String;
+}
+
+pub trait TryScribeString {
+    fn try_scribe(&self) -> Option<String>;
+}
+
+//TODO
+pub trait ScribeCowStr {
+    fn scribe(&self) -> Cow<'static, str>;
+}
+
+//TODO
+pub trait TryScribeCowStr {
+    fn try_scribe(&self) -> Option<Cow<'static, str>>;
+}

enumscribe_derive/Cargo.toml

@@ -0,0 +1,19 @@
+[package]
+name = "enumscribe_derive"
+version = "0.1.0"
+authors = ["Tom Panton <pantonshire@gmail.com>"]
+edition = "2018"
+license = "MIT"
+description = "Procedural macros for converting between enums and strings"
+
+[lib]
+proc-macro = true
+
+[dependencies]
+proc-macro2 = "1.0"
+syn = "1.0"
+quote = "1.0"
+
+[dev-dependencies]
+serde = "1.0"
+serde_json = "1.0"

enumscribe_derive/src/enums.rs

@@ -42,15 +42,15 @@ pub(crate) enum VariantConstructor {
 }
 
 impl<'a> Variant<'a> {
-    pub(crate) fn match_variant<F, G>(&self, named_fn: F, other_fn: G) -> Option<(TokenStream, TokenStream)>
+    pub(crate) fn match_variant<F, G>(&self, named_fn: F, other_fn: G) -> MacroResult<Option<(TokenStream, TokenStream)>>
         where
-            F: Fn(&str) -> TokenStream,
-            G: Fn(TokenStream) -> TokenStream
+            F: Fn(&str) -> MacroResult<TokenStream>,
+            G: Fn(TokenStream) -> MacroResult<TokenStream>
     {
         let variant_ident = &self.data.ident;
 
         match &self.v_type {
-            VariantType::Ignore => None,
+            VariantType::Ignore => Ok(None),
 
             VariantType::Named { name, constructor, .. } => {
                 let pattern = match constructor {
@@ -58,19 +58,19 @@ impl<'a> Variant<'a> {
                     VariantConstructor::Paren => quote! { #variant_ident () },
                     VariantConstructor::Brace => quote! { #variant_ident {} }
                 };
-                Some((pattern, named_fn(name)))
+                Ok(Some((pattern, named_fn(name)?)))
             }
 
             VariantType::Other { field_name } => {
                 let field_name_tokens = match field_name {
                     Some(field_name) => field_name.to_token_stream(),
-                    None => quote! { __other_inner }
+                    None => quote! { __enumscribe_other_inner }
                 };
                 let pattern = match field_name {
                     Some(_) => quote! { #variant_ident { #field_name_tokens } },
                     None => quote! { #variant_ident (#field_name_tokens) }
                 };
-                Some((pattern, other_fn(field_name_tokens)))
+                Ok(Some((pattern, other_fn(field_name_tokens)?)))
             }
         }
     }

enumscribe_derive/src/lib.rs

@@ -0,0 +1,138 @@
+use proc_macro::TokenStream;
+use std::iter;
+
+use quote::quote;
+use syn::{Data, DataEnum, DeriveInput};
+
+use error::{MacroError, MacroResult};
+
+mod enums;
+mod attribute;
+mod error;
+
+const CRATE_ATTR: &'static str = "enumscribe";
+
+const NAME: &'static str = "str";
+const OTHER: &'static str = "other";
+const IGNORE: &'static str = "ignore";
+const CASE_INSENSITIVE: &'static str = "case_insensitive";
+
+macro_rules! proc_try {
+    ($x:expr) => {
+        match $x {
+            Ok(val) => val,
+            Err(err) => return err.into()
+        }
+    };
+}
+
+#[proc_macro_derive(ScribeString, attributes(enumscribe))]
+pub fn derive_enum_to_string(input: TokenStream) -> TokenStream {
+    let input: DeriveInput = syn::parse(input)
+        .expect("failed to parse input");
+
+    let enum_data = proc_try!(get_enum_data(&input));
+    let parsed_enum = proc_try!(enums::parse_enum(enum_data));
+
+    let enum_ident = &input.ident;
+    let enum_idents = iter::repeat(enum_ident);
+
+    let mut match_patterns = Vec::with_capacity(parsed_enum.variants.len());
+    let mut match_results = Vec::with_capacity(parsed_enum.variants.len());
+
+    for variant in parsed_enum.variants.iter() {
+        match variant.match_variant(
+            |name| Ok(quote! { <_ as ::std::borrow::ToOwned>::to_owned(#name) }),
+            |field| Ok(quote! { <_ as ::std::convert::Into<::std::string::String>>::into(#field) }),
+        ) {
+            Ok(Some((pattern, result))) => {
+                match_patterns.push(pattern);
+                match_results.push(result);
+            },
+
+            Ok(None) => return MacroError::new(format!(
+                "cannot derive ScribeString for {} because the variant {} is marked as {}\n\
+                 explanation: since {} is ignored, it cannot be guaranteed that the enum can \
+                 always be successfully converted to a String\n\
+                 hint: try deriving TryScribeString instead",
+                enum_ident.to_string(), variant.data.ident.to_string(), IGNORE,
+                variant.data.ident.to_string(),
+            ), variant.span).into(),
+
+            Err(err) => return err.into()
+        }
+    }
+
+    (quote! {
+        impl ::enumscribe::ScribeString for #enum_ident {
+            fn scribe(&self) -> ::std::string::String {
+                match self {
+                    #(#enum_idents::#match_patterns => #match_results,)*
+                }
+            }
+        }
+    }).into()
+}
+
+#[proc_macro_derive(TryScribeString, attributes(enumscribe))]
+pub fn derive_try_enum_to_string(input: TokenStream) -> TokenStream {
+    let input: DeriveInput = syn::parse(input)
+        .expect("failed to parse input");
+
+    let enum_data = proc_try!(get_enum_data(&input));
+    let parsed_enum = proc_try!(enums::parse_enum(enum_data));
+
+    let enum_ident = &input.ident;
+    let enum_idents = iter::repeat(enum_ident);
+
+    let mut ignore_variant = false;
+    let mut match_patterns = Vec::with_capacity(parsed_enum.variants.len());
+    let mut match_results = Vec::with_capacity(parsed_enum.variants.len());
+
+    for variant in parsed_enum.variants.iter() {
+        match variant.match_variant(
+            |name| Ok(quote! { ::std::option::Option::Some(<_ as ::std::borrow::ToOwned>::to_owned(#name)) }),
+            |field| Ok(quote! { ::std::option::Option::Some(<_ as ::std::convert::Into<::std::string::String>>::into(#field)) }),
+        ) {
+            Ok(Some((pattern, result))) => {
+                match_patterns.push(pattern);
+                match_results.push(result);
+            },
+
+            Ok(None) => ignore_variant = true,
+
+            Err(err) => return err.into()
+        }
+    }
+
+    let ignore_arm = if ignore_variant {
+        quote! { _ => ::std::option::Option::None, }
+    } else {
+        quote! {}
+    };
+
+    (quote! {
+        impl ::enumscribe::TryScribeString for #enum_ident {
+            fn try_scribe(&self) -> ::std::option::Option<::std::string::String> {
+                match self {
+                    #(#enum_idents::#match_patterns => #match_results,)*
+                    #ignore_arm
+                }
+            }
+        }
+    }).into()
+}
+
+fn get_enum_data(input: &DeriveInput) -> MacroResult<&DataEnum> {
+    let enum_data = match &input.data {
+        Data::Enum(enum_data) => enum_data,
+        Data::Struct(_) => return Err(MacroError::new("enumscribe cannot be used for structs", input.ident.span())),
+        Data::Union(_) => return Err(MacroError::new("enumscribe cannot be used for unions", input.ident.span()))
+    };
+
+    if enum_data.variants.is_empty() {
+        return Err(MacroError::new("enumscribe cannot be used for empty enums", input.ident.span()));
+    }
+
+    Ok(enum_data)
+}

enumscribe_examples/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "enumscribe_examples"
+version = "0.1.0"
+authors = ["Tom Panton <pantonshire@gmail.com>"]
+edition = "2018"
+license = "MIT"
+
+[dev-dependencies]
+enumscribe = { path = "../enumscribe" }
+enumscribe_derive = { path = "../enumscribe_derive" }

enumscribe_examples/examples/airports.rs

@@ -1,7 +1,7 @@
-#[macro_use]
-extern crate enumscribe;
+use enumscribe::*;
 
-#[derive(EnumToString)]
+// #[derive(ScribeString)]
+#[derive(TryScribeString)]
 enum Airport {
     #[enumscribe(str = "LHR", case_insensitive)]
     Heathrow,
@@ -9,7 +9,7 @@ enum Airport {
     Gatwick,
     #[enumscribe(str = "LTN", case_insensitive)]
     Luton,
-    #[enumscribe(str = "BHX", case_insensitive)]
+    #[enumscribe(str = "BHX", case_insensitive, ignore)]
     BirminghamInternational,
     #[enumscribe(other)]
     Other(String),
@@ -17,6 +17,6 @@ enum Airport {
 
 fn main() {
     let luton = Airport::Luton;
-    let luton_str: String = luton.into();
-    println!("Hello, {}!", luton_str);
+    let luton_string = luton.try_scribe();
+    println!("Hello, {:?}!", luton_string);
 }

enumscribe_examples/src/main.rs

@@ -0,0 +1,3 @@
+fn main() {
+    println!("Hello, world!");
+}

enumscribe_tests/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "enumscribe_tests"
+version = "0.1.0"
+authors = ["Tom Panton <pantonshire@gmail.com>"]
+edition = "2018"
+license = "MIT"
+
+[dependencies]

enumscribe_tests/src/main.rs

@@ -0,0 +1,3 @@
+fn main() {
+    println!("Hello, world!");
+}

src/lib.rs

@@ -1,87 +0,0 @@
-use proc_macro::TokenStream;
-use std::iter;
-
-use quote::quote;
-use syn::{Data, DataEnum, DeriveInput};
-
-use error::{MacroError, MacroResult};
-
-use crate::enums::VariantType;
-
-mod enums;
-mod attribute;
-mod error;
-
-const CRATE_ATTR: &'static str = "enumscribe";
-
-const NAME: &'static str = "str";
-const OTHER: &'static str = "other";
-const IGNORE: &'static str = "ignore";
-const CASE_INSENSITIVE: &'static str = "case_insensitive";
-
-macro_rules! proc_try {
-    ($x:expr) => {
-        match $x {
-            Ok(val) => val,
-            Err(err) => return err.into()
-        }
-    };
-}
-
-#[proc_macro_derive(EnumToString, attributes(enumscribe))]
-pub fn derive_enum_to_string(input: TokenStream) -> TokenStream {
-    let input: DeriveInput = syn::parse(input)
-        .expect("failed to parse input");
-
-    let enum_data = proc_try!(get_enum_data(&input));
-    let parsed_enum = proc_try!(enums::parse_enum(enum_data));
-
-    let enum_ident = &input.ident;
-    let enum_idents = iter::repeat(enum_ident);
-
-    if parsed_enum.variants.is_empty() {
-        return MacroError::new(format!(
-            "cannot derive EnumToString for {} because it has no variants",
-            enum_ident.to_string()
-        ), input.ident.span()).into();
-    }
-
-    let mut match_patterns = Vec::with_capacity(parsed_enum.variants.len());
-    let mut match_results = Vec::with_capacity(parsed_enum.variants.len());
-
-    for variant in parsed_enum.variants.iter() {
-        if let Some((pattern, result)) = variant.match_variant(
-            |name| quote! { <_ as ::std::borrow::ToOwned>::to_owned(#name) },
-            |field| quote! { <_ as ::std::convert::Into<::std::string::String>>::into(#field) }
-        ) {
-            match_patterns.push(pattern);
-            match_results.push(result);
-        } else {
-            return MacroError::new(format!(
-                "cannot derive EnumToString for {} because the variant {} is marked as {}\n\
-                 explanation: since {} is ignored, it cannot be guaranteed that the enum can \
-                 always be successfully converted to a String", //TODO: suggest another derive to use instead
-                enum_ident.to_string(), variant.data.ident.to_string(), IGNORE,
-                variant.data.ident.to_string(),
-            ), variant.span).into();
-        }
-    }
-
-    (quote! {
-        impl ::std::convert::From<#enum_ident> for ::std::string::String {
-            fn from(__enum_to_scribe: #enum_ident) -> Self {
-                match __enum_to_scribe {
-                    #(#enum_idents::#match_patterns => #match_results),*
-                }
-            }
-        }
-    }).into()
-}
-
-fn get_enum_data(input: &DeriveInput) -> MacroResult<&DataEnum> {
-    match &input.data {
-        Data::Enum(data) => Ok(data),
-        Data::Struct(_) => Err(MacroError::new("enumscribe cannot be used for structs", input.ident.span())),
-        Data::Union(_) => Err(MacroError::new("enumscribe cannot be used for unions", input.ident.span()))
-    }
-}