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Add default value for properties #879

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Add default value for properties #879

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6a594be
Add `default` value for properties
AlephAlpha Jan 17, 2020
0d8f7e6
Fix misleading error message
AlephAlpha Jan 19, 2020
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169 changes: 106 additions & 63 deletions crates/macro/src/derive_props/field.rs
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Original file line number Diff line number Diff line change
@@ -1,23 +1,33 @@
use super::generics::GenericArguments;
use proc_macro2::{Ident, Span};
use quote::quote;
use quote::{quote, quote_spanned};
use std::cmp::{Ord, Ordering, PartialEq, PartialOrd};
use std::convert::TryFrom;
use syn::parse::Result;
use syn::spanned::Spanned;
use syn::{Error, Field, Meta, MetaList, NestedMeta, Type, Visibility};
use syn::{Error, Expr, Field, Lit, Meta, MetaList, MetaNameValue, NestedMeta, Type, Visibility};

#[derive(PartialEq, Eq)]
enum PropAttr {
Required { wrapped_name: Ident },
Default { default_value: Expr },
None,
}

#[derive(Eq)]
pub struct PropField {
ty: Type,
name: Ident,
wrapped_name: Option<Ident>,
attr: PropAttr,
}

impl PropField {
/// All required property fields are wrapped in an `Option`
pub fn is_required(&self) -> bool {
self.wrapped_name.is_some()
match self.attr {
PropAttr::Required { .. } => true,
_ => false,
}
}

/// This step name is descriptive to help a developer realize they missed a required prop
Expand All @@ -31,42 +41,62 @@ impl PropField {
/// Used to transform the `PropWrapper` struct into `Properties`
pub fn to_field_setter(&self) -> proc_macro2::TokenStream {
let name = &self.name;
if let Some(wrapped_name) = &self.wrapped_name {
quote! {
#name: self.wrapped.#wrapped_name.unwrap(),
match &self.attr {
PropAttr::Required { wrapped_name } => {
quote! {
#name: self.wrapped.#wrapped_name.unwrap(),
}
}
} else {
quote! {
#name: self.wrapped.#name,
_ => {
quote! {
#name: self.wrapped.#name,
}
}
}
}

/// Wrap all required props in `Option`
pub fn to_field_def(&self) -> proc_macro2::TokenStream {
let ty = &self.ty;
if let Some(wrapped_name) = &self.wrapped_name {
quote! {
#wrapped_name: ::std::option::Option<#ty>,
match &self.attr {
PropAttr::Required { wrapped_name } => {
quote! {
#wrapped_name: ::std::option::Option<#ty>,
}
}
} else {
let name = &self.name;
quote! {
#name: #ty,
_ => {
let name = &self.name;
quote! {
#name: #ty,
}
}
}
}

/// All optional props must implement the `Default` trait
pub fn to_default_setter(&self) -> proc_macro2::TokenStream {
if let Some(wrapped_name) = &self.wrapped_name {
quote! {
#wrapped_name: ::std::default::Default::default(),
match &self.attr {
PropAttr::Required { wrapped_name } => {
quote! {
#wrapped_name: ::std::option::Option::None,
}
}
} else {
let name = &self.name;
quote! {
#name: ::std::default::Default::default(),
PropAttr::Default { default_value } => {
let name = &self.name;
let ty = &self.ty;
let span = default_value.span();
quote_spanned! {span=>
#name: {
let none: Option<#ty> = None;
if false { none } else { Some(#default_value) }.unwrap()
},
}
}
PropAttr::None => {
let name = &self.name;
quote! {
#name: ::std::default::Default::default(),
}
}
}
}
Expand All @@ -78,64 +108,77 @@ impl PropField {
generic_arguments: &GenericArguments,
vis: &Visibility,
) -> proc_macro2::TokenStream {
let Self {
name,
ty,
wrapped_name,
} = self;
if let Some(wrapped_name) = wrapped_name {
quote! {
#[doc(hidden)]
#vis fn #name(mut self, #name: #ty) -> #builder_name<#generic_arguments> {
self.wrapped.#wrapped_name = ::std::option::Option::Some(#name);
#builder_name {
wrapped: self.wrapped,
_marker: ::std::marker::PhantomData,
let Self { name, ty, attr } = self;
match attr {
PropAttr::Required { wrapped_name } => {
quote! {
#[doc(hidden)]
#vis fn #name(mut self, #name: #ty) -> #builder_name<#generic_arguments> {
self.wrapped.#wrapped_name = ::std::option::Option::Some(#name);
#builder_name {
wrapped: self.wrapped,
_marker: ::std::marker::PhantomData,
}
}
}
}
} else {
quote! {
#[doc(hidden)]
#vis fn #name(mut self, #name: #ty) -> #builder_name<#generic_arguments> {
self.wrapped.#name = #name;
self
_ => {
quote! {
#[doc(hidden)]
#vis fn #name(mut self, #name: #ty) -> #builder_name<#generic_arguments> {
self.wrapped.#name = #name;
self
}
}
}
}
}

// Detect the `#[props(required)]` attribute which denotes required fields
fn required_wrapper(named_field: &syn::Field) -> Result<Option<Ident>> {
// 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(None);
return Ok(PropAttr::None);
};

let expected_required = syn::Error::new(meta_list.span(), "expected `props(required)`");
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_required);
return Err(expected_attr);
};
match first_nested {
NestedMeta::Meta(Meta::Path(word_path)) => {
if !word_path.is_ident("required") {
return Err(expected_attr);
}

let word_path = match first_nested {
NestedMeta::Meta(Meta::Path(path)) => path,
_ => return Err(expected_required),
};
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!()
}
}
NestedMeta::Meta(Meta::NameValue(name_value)) => {
let MetaNameValue { path, lit, .. } = name_value;

if !word_path.is_ident("required") {
return Err(expected_required);
}
if !path.is_ident("default") {
return Err(expected_attr);
}

if let Some(ident) = &named_field.ident {
Ok(Some(Ident::new(
&format!("{}_wrapper", ident),
Span::call_site(),
)))
} else {
unreachable!()
if let Lit::Str(lit_str) = lit {
let default_value = lit_str.parse()?;
Ok(PropAttr::Default { default_value })
} else {
Err(expected_attr)
}
}
_ => Err(expected_attr),
}
}

Expand All @@ -161,7 +204,7 @@ impl TryFrom<Field> for PropField {

fn try_from(field: Field) -> Result<Self> {
Ok(PropField {
wrapped_name: Self::required_wrapper(&field)?,
attr: Self::attribute(&field)?,
ty: field.ty,
name: field.ident.unwrap(),
})
Expand Down
30 changes: 30 additions & 0 deletions tests/derive_props/fail.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -50,4 +50,34 @@ mod t4 {
}
}

mod t5 {
use super::*;
#[derive(Clone, Properties)]
pub struct Props {
// ERROR: default must be given a value
#[props(default)]
value: String,
}
}

mod t6 {
use super::*;
#[derive(Clone, Properties)]
pub struct Props {
// ERROR: the value must be a string
#[props(default = 123)]
value: i32,
}
}

mod t7 {
use super::*;
#[derive(Clone, Properties)]
pub struct Props {
// ERROR: the value must be parsed as a String
#[props(default = "123")]
value: String,
}
}

fn main() {}
26 changes: 25 additions & 1 deletion tests/derive_props/fail.stderr
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Original file line number Diff line number Diff line change
@@ -1,9 +1,21 @@
error: expected `props(required)`
error: expected `props(required)` or `#[props(default="...")]`
--> $DIR/fail.rs:21:11
|
21 | #[props(optional)]
| ^^^^^

error: expected `props(required)` or `#[props(default="...")]`
--> $DIR/fail.rs:58:11
|
58 | #[props(default)]
| ^^^^^

error: expected `props(required)` or `#[props(default="...")]`
--> $DIR/fail.rs:68:11
|
68 | #[props(default = 123)]
| ^^^^^

error[E0277]: the trait bound `t1::Value: std::default::Default` is not satisfied
--> $DIR/fail.rs:9:21
|
Expand All @@ -29,3 +41,15 @@ error[E0599]: no method named `b` found for type `t4::PropsBuilder<t4::PropsBuil
...
49 | Props::builder().b(1).a(2).build();
| ^ help: there is a method with a similar name: `a`

error[E0308]: if and else have incompatible types
--> $DIR/fail.rs:78:27
|
78 | #[props(default = "123")]
| ^^^^^
| |
| expected struct `std::string::String`, found integer
| expected because of this
|
= note: expected type `std::option::Option<std::string::String>`
found type `std::option::Option<{integer}>`
28 changes: 26 additions & 2 deletions tests/derive_props/pass.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -91,14 +91,38 @@ mod t6 {
#[derive(Properties, Clone)]
pub struct Props<T: FromStr + Clone>
where
<T as FromStr>::Err: Clone,
<T as FromStr>::Err: Clone,
{
#[props(required)]
value: Result<T, <T as FromStr>::Err>,
}

fn required_prop_generics_with_where_clause_should_work() {
Props::<String>::builder().value(Ok(String::from(""))).build();
Props::<String>::builder()
.value(Ok(String::from("")))
.build();
}
}

mod t7 {
use super::*;

#[derive(Clone, Debug, Eq, PartialEq)]
pub enum Foo {
One,
Two,
}

#[derive(Clone, Properties)]
pub struct Props {
#[props(default = "Foo::One")]
value: Foo,
}

fn default_value_should_work() {
let props = Props::builder().build();
assert_eq!(props.value, Foo::One);
Props::builder().value(Foo::Two).build();
}
}

Expand Down