Properties 2.0

crates/macro/src/derive_props/field.rs

@@ -5,15 +5,15 @@ use std::cmp::{Ord, Ordering, PartialEq, PartialOrd};
 use std::convert::TryFrom;
 use syn::parse::Result;
 use syn::spanned::Spanned;
-use syn::{
-    Error, ExprPath, Field, Lit, Meta, MetaList, MetaNameValue, NestedMeta, Type, Visibility,
-};
+use syn::{Error, Expr, Field, Type, Visibility};
 
+#[allow(clippy::large_enum_variant)]
 #[derive(PartialEq, Eq)]
 enum PropAttr {
     Required { wrapped_name: Ident },
-    Default { default: ExprPath },
-    None,
+    PropOr(Expr),
+    PropOrElse(Expr),
+    PropOrDefault,
 }
 
 #[derive(Eq)]
@@ -83,25 +83,31 @@ impl PropField {
                     #wrapped_name: ::std::option::Option::None,
                 }
             }
-            PropAttr::Default { default } => {
+            PropAttr::PropOr(value) => {
                 let name = &self.name;
-                let ty = &self.ty;
-                let span = default.span();
-                // Hacks to avoid misleading error message.
+                let span = value.span();
                 quote_spanned! {span=>
                     #name: {
                         match true {
-                            #[allow(unreachable_code)]
-                            false => {
-                                let __unreachable: #ty = ::std::unreachable!();
-                                __unreachable
-                            },
-                            true => #default()
+                            false => ::std::unreachable!(),
+                            true => #value,
                         }
                     },
                 }
             }
-            PropAttr::None => {
+            PropAttr::PropOrElse(func) => {
+                let name = &self.name;
+                let span = func.span();
+                quote_spanned! {span=>
+                    #name: {
+                        match true {
+                            false => ::std::unreachable!(),
+                            true => (#func)(),
+                        }
+                    },
+                }
+            }
+            PropAttr::PropOrDefault => {
                 let name = &self.name;
                 quote! {
                     #name: ::std::default::Default::default(),
@@ -143,67 +149,28 @@ impl PropField {
         }
     }
 
-    // Detect `#[props(required)]` or `#[props(default="...")]` attribute
-    fn attribute(named_field: &syn::Field) -> Result<PropAttr> {
-        let meta_list = if let Some(meta_list) = Self::find_props_meta_list(named_field) {
-            meta_list
-        } else {
-            return Ok(PropAttr::None);
-        };
-
-        let expected_attr = syn::Error::new(
-            meta_list.span(),
-            "expected `props(required)` or `#[props(default=\"...\")]`",
-        );
-        let first_nested = if let Some(first_nested) = meta_list.nested.first() {
-            first_nested
-        } else {
-            return Err(expected_attr);
-        };
-        match first_nested {
-            NestedMeta::Meta(Meta::Path(word_path)) => {
-                if !word_path.is_ident("required") {
-                    return Err(expected_attr);
-                }
-
-                if let Some(ident) = &named_field.ident {
-                    let wrapped_name = Ident::new(&format!("{}_wrapper", ident), Span::call_site());
-                    Ok(PropAttr::Required { wrapped_name })
-                } else {
-                    unreachable!()
-                }
+    // Detect Properties 2.0 attributes
+    fn attribute(named_field: &Field) -> Result<PropAttr> {
+        let attr = named_field.attrs.iter().find(|attr| {
+            attr.path.is_ident("prop_or")
+                || attr.path.is_ident("prop_or_else")
+                || attr.path.is_ident("prop_or_default")
+        });
+
+        if let Some(attr) = attr {
+            if attr.path.is_ident("prop_or") {
+                Ok(PropAttr::PropOr(attr.parse_args()?))
+            } else if attr.path.is_ident("prop_or_else") {
+                Ok(PropAttr::PropOrElse(attr.parse_args()?))
+            } else if attr.path.is_ident("prop_or_default") {
+                Ok(PropAttr::PropOrDefault)
+            } else {
+                unreachable!()
             }
-            NestedMeta::Meta(Meta::NameValue(name_value)) => {
-                let MetaNameValue { path, lit, .. } = name_value;
-
-                if !path.is_ident("default") {
-                    return Err(expected_attr);
-                }
-
-                if let Lit::Str(lit_str) = lit {
-                    let default = lit_str.parse()?;
-                    Ok(PropAttr::Default { default })
-                } else {
-                    Err(expected_attr)
-                }
-            }
-            _ => Err(expected_attr),
-        }
-    }
-
-    fn find_props_meta_list(field: &syn::Field) -> Option<MetaList> {
-        let meta_list = field
-            .attrs
-            .iter()
-            .find_map(|attr| match attr.parse_meta().ok()? {
-                Meta::List(meta_list) => Some(meta_list),
-                _ => None,
-            })?;
-
-        if meta_list.path.is_ident("props") {
-            Some(meta_list)
         } else {
-            None
+            let ident = named_field.ident.as_ref().unwrap();
+            let wrapped_name = Ident::new(&format!("{}_wrapper", ident), Span::call_site());
+            Ok(PropAttr::Required { wrapped_name })
         }
     }
 }

crates/macro/src/lib.rs

@@ -15,8 +15,7 @@
 //!
 //! #[derive(Clone, Properties)]
 //! struct Props {
-//!   #[props(required)]
-//!   prop: String,
+//!     prop: String,
 //! };
 //!
 //! # enum Msg { Submit }
@@ -88,7 +87,7 @@ fn non_capitalized_ascii(string: &str) -> bool {
     }
 }
 
-#[proc_macro_derive(Properties, attributes(props))]
+#[proc_macro_derive(Properties, attributes(prop_or, prop_or_else, prop_or_default))]
 pub fn derive_props(input: TokenStream) -> TokenStream {
     let input = parse_macro_input!(input as DerivePropsInput);
     TokenStream::from(input.into_token_stream())

crates/macro/tests/derive_props/fail.rs

@@ -9,6 +9,7 @@ mod t1 {
     #[derive(Clone, Properties)]
     pub struct Props {
         // ERROR: optional params must implement default
+        #[prop_or_default]
         value: Value,
     }
 }
@@ -17,8 +18,8 @@ mod t2 {
     use super::*;
     #[derive(Clone, Properties)]
     pub struct Props {
-        // ERROR: optional is not a tag
-        #[props(optional)]
+        // ERROR: old syntax no longer supported
+        #[props(default)]
         value: String,
     }
 }
@@ -27,7 +28,6 @@ mod t3 {
     use super::*;
     #[derive(Clone, Properties)]
     pub struct Props {
-        #[props(required)]
         value: String,
     }
 
@@ -41,7 +41,6 @@ mod t4 {
     #[derive(Clone, Properties)]
     pub struct Props {
         b: i32,
-        #[props(required)]
         a: i32,
     }
 
@@ -54,8 +53,8 @@ mod t5 {
     use super::*;
     #[derive(Clone, Properties)]
     pub struct Props {
-        // ERROR: default must be given a value
-        #[props(default)]
+        // ERROR: prop_or must be given a value
+        #[prop_or()]
         value: String,
     }
 }
@@ -64,19 +63,19 @@ mod t6 {
     use super::*;
     #[derive(Clone, Properties)]
     pub struct Props {
-        // ERROR: 123 is not a path or an identifier
-        #[props(default = 123)]
-        value: i32,
+        // ERROR: 123 is not a String
+        #[prop_or(123)]
+        value: String,
     }
 }
 
 mod t7 {
     use super::*;
     #[derive(Clone, Properties)]
     pub struct Props {
-        // ERROR: the value must be parsed into a path to a function
-        #[props(default = "123")]
-        value: String,
+        // ERROR: 123 is not a function
+        #[prop_or_else(123)]
+        value: i32,
     }
 }
 
@@ -85,7 +84,7 @@ mod t8 {
     #[derive(Clone, Properties)]
     pub struct Props {
         // ERROR: cannot find function foo in this scope
-        #[props(default = "foo")]
+        #[prop_or_else(foo)]
         value: String,
     }
 }
@@ -95,7 +94,7 @@ mod t9 {
     #[derive(Clone, Properties)]
     pub struct Props {
         // ERROR: the function must take no arguments
-        #[props(default = "foo")]
+        #[prop_or_else(foo)]
         value: String,
     }
 
@@ -109,7 +108,7 @@ mod t10 {
     #[derive(Clone, Properties)]
     pub struct Props {
         // ERROR: the function returns incompatible types
-        #[props(default = "foo")]
+        #[prop_or_else(foo)]
         value: String,
     }
 

crates/macro/tests/derive_props/fail.stderr

@@ -1,38 +1,26 @@
-error: expected `props(required)` or `#[props(default="...")]`
-  --> $DIR/fail.rs:21:11
+error: unexpected end of input, expected expression
+  --> $DIR/fail.rs:57:18
    |
-21 |         #[props(optional)]
-   |           ^^^^^
+57 |         #[prop_or()]
+   |                  ^^
 
-error: expected `props(required)` or `#[props(default="...")]`
-  --> $DIR/fail.rs:58:11
+error: cannot find attribute `props` in this scope
+  --> $DIR/fail.rs:22:11
    |
-58 |         #[props(default)]
+22 |         #[props(default)]
    |           ^^^^^
 
-error: expected `props(required)` or `#[props(default="...")]`
-  --> $DIR/fail.rs:68:11
+error[E0425]: cannot find value `foo` in this scope
+  --> $DIR/fail.rs:87:24
    |
-68 |         #[props(default = 123)]
-   |           ^^^^^
-
-error: expected identifier
-  --> $DIR/fail.rs:78:27
-   |
-78 |         #[props(default = "123")]
-   |                           ^^^^^
-
-error[E0425]: cannot find function `foo` in this scope
-  --> $DIR/fail.rs:88:27
-   |
-88 |         #[props(default = "foo")]
-   |                           ^^^^^ not found in this scope
+87 |         #[prop_or_else(foo)]
+   |                        ^^^ not found in this scope
    |
 help: possible candidates are found in other modules, you can import them into scope
    |
-84 |     use crate::t10::foo;
+83 |     use crate::t10::foo;
    |
-84 |     use crate::t9::foo;
+83 |     use crate::t9::foo;
    |
 
 error[E0277]: the trait bound `t1::Value: std::default::Default` is not satisfied
@@ -46,7 +34,7 @@ error[E0277]: the trait bound `t1::Value: std::default::Default` is not satisfie
 error[E0599]: no method named `build` found for type `t3::PropsBuilder<t3::PropsBuilderStep_missing_required_prop_value>` in the current scope
   --> $DIR/fail.rs:35:26
    |
-28 |     #[derive(Clone, Properties)]
+29 |     #[derive(Clone, Properties)]
    |                     ---------- method `build` not found for this
 ...
 35 |         Props::builder().build();
@@ -57,30 +45,51 @@ error[E0599]: no method named `build` found for type `t3::PropsBuilder<t3::Props
            candidate #1: `proc_macro::bridge::server::TokenStreamBuilder`
 
 error[E0599]: no method named `b` found for type `t4::PropsBuilder<t4::PropsBuilderStep_missing_required_prop_a>` in the current scope
-  --> $DIR/fail.rs:49:26
+  --> $DIR/fail.rs:48:26
    |
 41 |     #[derive(Clone, Properties)]
    |                     ---------- method `b` not found for this
 ...
-49 |         Props::builder().b(1).a(2).build();
+48 |         Props::builder().b(1).a(2).build();
    |                          ^ help: there is a method with a similar name: `a`
 
+error[E0308]: match arms have incompatible types
+  --> $DIR/fail.rs:67:19
+   |
+67 |         #[prop_or(123)]
+   |                   ^^^
+   |                   |
+   |                   expected struct `std::string::String`, found integer
+   |                   `match` arms have incompatible types
+   |                   this is found to be of type `std::string::String`
+   |                   help: try using a conversion method: `123.to_string()`
+   |
+   = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
+
+error[E0618]: expected function, found `{integer}`
+  --> $DIR/fail.rs:77:24
+   |
+77 |         #[prop_or_else(123)]
+   |                        ^^^ call expression requires function
+
 error[E0061]: this function takes 1 parameter but 0 parameters were supplied
-   --> $DIR/fail.rs:98:27
+   --> $DIR/fail.rs:97:24
     |
-98  |         #[props(default = "foo")]
-    |                           ^^^^^ expected 1 parameter
+97  |         #[prop_or_else(foo)]
+    |                        ^^^ expected 1 parameter
 ...
-102 |     fn foo(bar: i32) -> String {
+101 |     fn foo(bar: i32) -> String {
     |     -------------------------- defined here
 
 error[E0308]: match arms have incompatible types
-   --> $DIR/fail.rs:112:27
+   --> $DIR/fail.rs:111:24
+    |
+111 |         #[prop_or_else(foo)]
+    |                        ^^^
+    |                        |
+    |                        expected struct `std::string::String`, found `i32`
+    |                        `match` arms have incompatible types
+    |                        this is found to be of type `std::string::String`
+    |                        help: try using a conversion method: `foo.to_string()`
     |
-112 |         #[props(default = "foo")]
-    |                           ^^^^^
-    |                           |
-    |                           expected struct `std::string::String`, found `i32`
-    |                           `match` arms have incompatible types
-    |                           this is found to be of type `std::string::String`
-    |                           help: try using a conversion method: `"foo".to_string()`
+    = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)