Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Add default value for properties (takes a function instead of an expression) #881

Merged
merged 4 commits into from
Jan 19, 2020
Merged

Add default value for properties (takes a function instead of an expression) #881

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
4 commits
Select commit Hold shift + click to select a range
6a594be
Add `default` value for properties
AlephAlpha Jan 17, 2020
2eff9ea
Default values specified by paths instead of exprs
AlephAlpha Jan 18, 2020
854eb01
Fix misleading error message
AlephAlpha Jan 19, 2020
891d70a
Remove confusing Option
AlephAlpha Jan 19, 2020
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
178 changes: 115 additions & 63 deletions crates/macro/src/derive_props/field.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,23 +1,35 @@
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, ExprPath, Field, Lit, Meta, MetaList, MetaNameValue, NestedMeta, Type, Visibility,
};

#[derive(PartialEq, Eq)]
enum PropAttr {
Required { wrapped_name: Ident },
Default { default: ExprPath },
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`
jstarry marked this conversation as resolved.
Show resolved Hide resolved
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 +43,69 @@ 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,
jstarry marked this conversation as resolved.
Show resolved Hide resolved
}
}
} else {
let name = &self.name;
quote! {
#name: ::std::default::Default::default(),
PropAttr::Default { default } => {
let name = &self.name;
let ty = &self.ty;
let span = default.span();
// Hacks to avoid misleading error message.
quote_spanned! {span=>
#name: {
match true {
#[allow(unreachable_code)]
false => {
let __unreachable: #ty = ::std::unreachable!();
__unreachable
Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Do you need an assign here? I think you can just do false => ::std::unreachable!() right?

Copy link
Contributor Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

The false arm must return the correct type, otherwise Rust would think that it has the same type as #default(), and might show that misleading message: "help: try using a conversion method: "foo".to_string()".

Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Hmm your explanation makes sense but I had it working with unimplemented like that. This is fine though!

Copy link
Contributor Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Sorry, I was wrong about that. I did not test it before leaving the comment. It seems that false => ::std::unreachable!() does work.

},
true => #default()
}
},
}
}
PropAttr::None => {
let name = &self.name;
quote! {
#name: ::std::default::Default::default(),
}
}
}
}
Expand All @@ -78,64 +117,77 @@ 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 = lit_str.parse()?;
Ok(PropAttr::Default { default })
} else {
Err(expected_attr)
}
}
_ => Err(expected_attr),
}
}

Expand All @@ -161,7 +213,7 @@ 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
68 changes: 68 additions & 0 deletions tests/derive_props/fail.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -50,4 +50,72 @@ 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: 123 is not a path or an identifier
#[props(default = 123)]
value: i32,
}
}

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,
}
}

mod t8 {
use super::*;
#[derive(Clone, Properties)]
pub struct Props {
// ERROR: cannot find function foo in this scope
#[props(default = "foo")]
value: String,
}
}

mod t9 {
use super::*;
#[derive(Clone, Properties)]
pub struct Props {
// ERROR: the function must take no arguments
#[props(default = "foo")]
value: String,
}

fn foo(bar: i32) -> String {
unimplemented!()
}
}

mod t10 {
use super::*;
#[derive(Clone, Properties)]
pub struct Props {
// ERROR: the function returns incompatible types
#[props(default = "foo")]
value: String,
}

fn foo() -> i32 {
unimplemented!()
}
}

fn main() {}
55 changes: 54 additions & 1 deletion tests/derive_props/fail.stderr
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,9 +1,40 @@
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: 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
|
help: possible candidates are found in other modules, you can import them into scope
|
84 | use crate::t10::foo;
|
84 | use crate::t9::foo;
|

error[E0277]: the trait bound `t1::Value: std::default::Default` is not satisfied
--> $DIR/fail.rs:9:21
|
Expand All @@ -29,3 +60,25 @@ 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[E0061]: this function takes 1 parameter but 0 parameters were supplied
--> $DIR/fail.rs:98:27
|
98 | #[props(default = "foo")]
| ^^^^^ expected 1 parameter
...
102 | fn foo(bar: i32) -> String {
| -------------------------- defined here

error[E0308]: match arms have incompatible types
--> $DIR/fail.rs:112:27
|
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`
|
= note: expected type `std::string::String`
found type `i32`
Loading