feat: add derive macro SelectAsFormField (#397)

Author: kumarUjjawal

cot-macros/src/lib.rs

@@ -6,6 +6,7 @@ mod from_request;
 mod main_fn;
 mod model;
 mod query;
+mod select_as_form_field;
 mod select_choice;
 
 use darling::Error;
@@ -23,6 +24,7 @@ use crate::from_request::impl_from_request_head_for_struct;
 use crate::main_fn::{fn_to_cot_e2e_test, fn_to_cot_main, fn_to_cot_test};
 use crate::model::impl_model_for_struct;
 use crate::query::{Query, query_to_tokens};
+use crate::select_as_form_field::impl_select_as_form_field_for_enum;
 use crate::select_choice::impl_select_choice_for_enum;
 
 #[proc_macro_derive(Form, attributes(form))]
@@ -213,6 +215,13 @@ pub fn derive_select_choice(input: TokenStream) -> TokenStream {
     token_stream.into()
 }
 
+#[proc_macro_derive(SelectAsFormField)]
+pub fn derive_select_as_form_field(input: TokenStream) -> TokenStream {
+    let ast = syn::parse_macro_input!(input as DeriveInput);
+    let token_stream = impl_select_as_form_field_for_enum(&ast);
+    token_stream.into()
+}
+
 #[proc_macro_derive(IntoResponse)]
 pub fn derive_into_response(input: TokenStream) -> TokenStream {
     let ast = parse_macro_input!(input as DeriveInput);

cot-macros/src/select_as_form_field.rs

@@ -0,0 +1,42 @@
+use darling::Error;
+use quote::quote;
+use syn::{Data, DeriveInput};
+
+use crate::cot_ident;
+
+pub(super) fn impl_select_as_form_field_for_enum(ast: &DeriveInput) -> proc_macro2::TokenStream {
+    let enum_name = &ast.ident;
+    let cot = cot_ident();
+
+    match &ast.data {
+        Data::Enum(_) => {}
+        _ => {
+            return Error::custom("`SelectAsFormField` can only be derived for enums")
+                .write_errors();
+        }
+    }
+
+    let impl_single = quote! {
+        #[automatically_derived]
+        impl #cot::form::AsFormField for #enum_name {
+            type Type = #cot::form::fields::SelectField<Self>;
+
+            fn clean_value(
+                field: &Self::Type
+            ) -> ::core::result::Result<Self, #cot::form::FormFieldValidationError> {
+                match #cot::form::FormField::value(field) {
+                    ::core::option::Option::Some(v) if !v.is_empty() => <Self as #cot::form::fields::SelectChoice>::from_str(v),
+                    _ => ::core::result::Result::Err(#cot::form::FormFieldValidationError::Required),
+                }
+            }
+
+            fn to_field_value(&self) -> ::std::string::String {
+                <Self as #cot::form::fields::SelectChoice>::to_string(self)
+            }
+        }
+    };
+
+    quote! {
+        #impl_single
+    }
+}

cot-macros/tests/compile_tests.rs

@@ -113,6 +113,21 @@ fn derive_select_choice() {
     t.compile_fail("tests/ui/derive_select_choice_empty_enum.rs");
 }
 
+#[rustversion::attr(
+    not(nightly),
+    ignore = "only test on nightly for consistent error messages"
+)]
+#[test]
+#[cfg_attr(
+    miri,
+    ignore = "unsupported operation: extern static `pidfd_spawnp` is not supported by Miri"
+)]
+fn derive_select_as_form_field() {
+    let t = trybuild::TestCases::new();
+    t.pass("tests/ui/derive_select_as_form_field.rs");
+    t.compile_fail("tests/ui/derive_select_as_form_field_struct.rs");
+}
+
 #[rustversion::attr(
     not(nightly),
     ignore = "only test on nightly for consistent error messages"

cot-macros/tests/ui/derive_select_as_form_field.rs

@@ -0,0 +1,10 @@
+use cot::form::fields::{SelectChoice, SelectAsFormField};
+
+#[derive(SelectChoice, SelectAsFormField, Debug, Clone, PartialEq, Eq, Hash)]
+enum Status {
+    Draft,
+    Published,
+    Archived,
+}
+
+fn main() {}

cot-macros/tests/ui/derive_select_as_form_field_struct.rs

@@ -0,0 +1,8 @@
+use cot_macros::SelectAsFormField;
+
+#[derive(SelectAsFormField)]
+struct NotAnEnum {
+    x: u8,
+}
+
+fn main() {}

cot-macros/tests/ui/derive_select_as_form_field_struct.stderr

@@ -0,0 +1,7 @@
+error: `SelectAsFormField` can only be derived for enums
+ --> tests/ui/derive_select_as_form_field_struct.rs:3:10
+  |
+3 | #[derive(SelectAsFormField)]
+  |          ^^^^^^^^^^^^^^^^^
+  |
+  = note: this error originates in the derive macro `SelectAsFormField` (in Nightly builds, run with -Z macro-backtrace for more info)

cot/src/form/fields.rs

@@ -18,7 +18,8 @@ pub use chrono::{
 pub use files::{FileField, FileFieldOptions, InMemoryUploadedFile};
 pub(crate) use select::check_required_multiple;
 pub use select::{
-    SelectChoice, SelectField, SelectFieldOptions, SelectMultipleField, SelectMultipleFieldOptions,
+    SelectAsFormField, SelectChoice, SelectField, SelectFieldOptions, SelectMultipleField,
+    SelectMultipleFieldOptions,
 };
 
 use crate::auth::PasswordHash;

cot/src/form/fields/chrono.rs

@@ -10,9 +10,7 @@ use cot::form::FormField;
 use cot::form::fields::impl_form_field;
 use cot::html::HtmlTag;
 
-use crate::form::fields::{
-    SelectChoice, SelectField, SelectMultipleField, Step, check_required, check_required_multiple,
-};
+use crate::form::fields::{SelectChoice, SelectField, Step, check_required};
 use crate::form::{AsFormField, FormFieldValidationError};
 
 impl AsFormField for Weekday {
@@ -29,39 +27,7 @@ impl AsFormField for Weekday {
     }
 }
 
-macro_rules! impl_as_form_field_mult {
-    ($field_type:ty) => {
-        impl_as_form_field_mult_collection!(::std::vec::Vec<$field_type>, $field_type);
-        impl_as_form_field_mult_collection!(::std::collections::VecDeque<$field_type>, $field_type);
-        impl_as_form_field_mult_collection!(
-            ::std::collections::LinkedList<$field_type>,
-            $field_type
-        );
-        impl_as_form_field_mult_collection!(::std::collections::HashSet<$field_type>, $field_type);
-        impl_as_form_field_mult_collection!(::indexmap::IndexSet<$field_type>, $field_type);
-    };
-}
-
-macro_rules! impl_as_form_field_mult_collection {
-    ($collection_type:ty, $field_type:ty) => {
-        impl AsFormField for $collection_type {
-            type Type = SelectMultipleField<$field_type>;
-
-            fn clean_value(field: &Self::Type) -> Result<Self, FormFieldValidationError> {
-                let value = check_required_multiple(field)?;
-
-                value.iter().map(|id| <$field_type>::from_str(id)).collect()
-            }
-
-            fn to_field_value(&self) -> String {
-                String::new()
-            }
-        }
-    };
-}
-
-impl_as_form_field_mult!(Weekday);
-impl_as_form_field_mult_collection!(WeekdaySet, Weekday);
+crate::form::fields::select::impl_as_form_field_mult_collection!(() => WeekdaySet, Weekday);
 
 const MONDAY_ID: &str = "mon";
 const TUESDAY_ID: &str = "tue";
@@ -730,7 +696,9 @@ mod tests {
     use cot::form::FormFieldValue;
 
     use super::*;
-    use crate::form::fields::{SelectFieldOptions, SelectMultipleFieldOptions};
+    use crate::form::fields::{
+        SelectFieldOptions, SelectMultipleField, SelectMultipleFieldOptions,
+    };
     use crate::form::{FormField, FormFieldOptions};
 
     #[test]