Automate SparseField implementations with serde rename support (#872)

* Move SparseField trait implementations to appropriate modules

Relocate SparseField implementations from request::endpoint modules to their
corresponding type modules for better organization and module cohesion.

Changes:
- Move impl SparseField for SparsePostFieldWith*Context from posts_endpoint to posts module
- Move impl SparseField for SparseMediaFieldWith*Context from media_endpoint to media module
- Move impl SparseField for SparseTemplateFieldWith*Context from templates_endpoint to templates module
- Move impl SparseField for SparseSearchResultFieldWith*Context from search_endpoint to search_results module
- Move impl SparseField for SparseCommentFieldWith*Context from comments_endpoint to comments module
- Add SparseField import to each type module
- Clean up unused SparseField imports from endpoint modules
- Preserve all field name mappings and custom serialization logic

* Add comprehensive unit tests for SparseField trait mappings

Add unit tests to validate all custom field name mappings in SparseField
trait implementations across all WordPress REST API entity types.

Changes:
- Add tests for Posts: PostType → "type" mapping across all contexts
- Add tests for Media: PostId → "post", PostType → "type" mappings
- Add tests for Templates: TemplateType → "type", PostId → "wp_id" mappings
- Add tests for Search Results: ObjectType → "type", ObjectSubtype → "subtype" mappings
- Add tests for Comments: CommentType → "type" mapping across all contexts
- Include regular field mappings (Id → "id") to verify default behavior
- Test all applicable contexts (edit, embed, view) for each entity type
- Use rstest parameterized tests for clean, declarative test cases
- Follow naming pattern test_as_mapped_field_name_* for future method rename

All 35 tests pass, confirming current manual SparseField implementations
work correctly. These tests will serve as regression protection when
transitioning to macro-generated implementations.

* Automate SparseField implementations via WpContextual macro

Phase 1: Remove redundant manual SparseField implementations by enhancing
the WpContextual macro to automatically generate SparseField trait
implementations that extract and use serde rename attributes.

Changes:
- Enhanced WpContextual macro to extract serde rename attributes and generate appropriate SparseField implementations
- Removed manual SparseField implementations from comments, media, posts, search_results, and templates modules
- Eliminated redundant default_sparse_field_implementation_from_field_name macro and all its usage
- Cleaned up imports and moved SparseField imports to test modules where needed

The macro now automatically handles field name mapping using serde rename
attributes, eliminating the need for manual implementations and reducing
code duplication while maintaining full test compatibility.

* Rename SparseField method to be more explicit about its purpose

Rename `as_str()` to `as_mapped_field_name()` to clearly indicate that this
method returns the API field name that may differ from the Rust field name
due to serde rename attributes.

Changes:
- Update SparseField trait method signature from `as_str()` to `as_mapped_field_name()`
- Update all implementations and test assertions to use the new method name
- Update WpContextual macro to generate the renamed method
- Update request builder to use the new method for `_fields` query parameters
- Improve library documentation to clarify serde rename support
- Remove unused `as_field_name()` method generation from WpContextual macro

This makes the API more self-documenting and clearly distinguishes between
raw field names and their mapped API equivalents.

* Fix wp_contextual tests by adding SparseField trait for tests

Author: oguzkocer

wp_api/src/comments.rs

@@ -482,13 +482,12 @@ fn comment_type_to_string(comment_type: CommentType) -> String {
 mod tests {
     use super::*;
     use crate::{
-        generate,
+        SparseField, generate,
         unit_test_common::{
             assert_expected_and_from_query_pairs, unit_test_example_date_as_option,
             unit_test_example_date_as_query_value,
         },
     };
-
     use rstest::*;
 
     #[rstest]
@@ -566,4 +565,34 @@ mod tests {
             "page=11&per_page=22&search=s_q&{after}&author=111%2C112&author_exclude=211%2C212&author_email=a_email%40example.com&{before}&exclude=1111%2C1112&include=2111%2C2112&offset=11111&order=desc&orderby=type&parent=44444%2C44445&parent_exclude=55555%2C55556&post=66666%2C66667&status=spam&type=pingback&password=p_q"
         )
     }
+
+    #[rstest]
+    #[case(SparseCommentFieldWithEditContext::Id, "id")]
+    #[case(SparseCommentFieldWithEditContext::CommentType, "type")]
+    fn test_as_mapped_field_name_for_edit_context(
+        #[case] field: SparseCommentFieldWithEditContext,
+        #[case] expected_mapped_field_name: &str,
+    ) {
+        assert_eq!(field.as_mapped_field_name(), expected_mapped_field_name);
+    }
+
+    #[rstest]
+    #[case(SparseCommentFieldWithEmbedContext::Id, "id")]
+    #[case(SparseCommentFieldWithEmbedContext::CommentType, "type")]
+    fn test_as_mapped_field_name_for_embed_context(
+        #[case] field: SparseCommentFieldWithEmbedContext,
+        #[case] expected_mapped_field_name: &str,
+    ) {
+        assert_eq!(field.as_mapped_field_name(), expected_mapped_field_name);
+    }
+
+    #[rstest]
+    #[case(SparseCommentFieldWithViewContext::Id, "id")]
+    #[case(SparseCommentFieldWithViewContext::CommentType, "type")]
+    fn test_as_mapped_field_name_for_view_context(
+        #[case] field: SparseCommentFieldWithViewContext,
+        #[case] expected_mapped_field_name: &str,
+    ) {
+        assert_eq!(field.as_mapped_field_name(), expected_mapped_field_name);
+    }
 }

wp_api/src/lib.rs

@@ -91,7 +91,7 @@ pub enum WpApiParamOrder {
 impl_as_query_value_from_to_string!(WpApiParamOrder);
 
 trait SparseField {
-    fn as_str(&self) -> &str;
+    fn as_mapped_field_name(&self) -> &str;
 }
 
 trait OptionFromStr {

wp_api/src/media.rs

@@ -528,7 +528,7 @@ pub struct SparseMediaCaption {
 mod tests {
     use super::*;
     use crate::{
-        generate,
+        SparseField, generate,
         posts::PostId,
         unit_test_common::{
             assert_expected_and_from_query_pairs, unit_test_example_date_as_option,
@@ -675,4 +675,36 @@ mod tests {
             serde_json::Value::Object(serde_json::Map::new())
         );
     }
+
+    #[rstest]
+    #[case(SparseMediaFieldWithEditContext::Id, "id")]
+    #[case(SparseMediaFieldWithEditContext::PostId, "post")]
+    #[case(SparseMediaFieldWithEditContext::PostType, "type")]
+    fn test_as_mapped_field_name_for_edit_context(
+        #[case] field: SparseMediaFieldWithEditContext,
+        #[case] expected_mapped_field_name: &str,
+    ) {
+        assert_eq!(field.as_mapped_field_name(), expected_mapped_field_name);
+    }
+
+    #[rstest]
+    #[case(SparseMediaFieldWithEmbedContext::Id, "id")]
+    #[case(SparseMediaFieldWithEmbedContext::PostType, "type")]
+    fn test_as_mapped_field_name_for_embed_context(
+        #[case] field: SparseMediaFieldWithEmbedContext,
+        #[case] expected_mapped_field_name: &str,
+    ) {
+        assert_eq!(field.as_mapped_field_name(), expected_mapped_field_name);
+    }
+
+    #[rstest]
+    #[case(SparseMediaFieldWithViewContext::Id, "id")]
+    #[case(SparseMediaFieldWithViewContext::PostId, "post")]
+    #[case(SparseMediaFieldWithViewContext::PostType, "type")]
+    fn test_as_mapped_field_name_for_view_context(
+        #[case] field: SparseMediaFieldWithViewContext,
+        #[case] expected_mapped_field_name: &str,
+    ) {
+        assert_eq!(field.as_mapped_field_name(), expected_mapped_field_name);
+    }
 }

wp_api/src/posts.rs

@@ -579,7 +579,7 @@ impl PostFormat {
 mod tests {
     use super::*;
     use crate::{
-        generate,
+        SparseField, generate,
         unit_test_common::{
             assert_expected_and_from_query_pairs, unit_test_example_date_as_option,
             unit_test_example_date_as_query_value,
@@ -644,6 +644,36 @@ mod tests {
         assert_expected_and_from_query_pairs(params, expected_query);
     }
 
+    #[rstest]
+    #[case(SparsePostFieldWithEditContext::Id, "id")]
+    #[case(SparsePostFieldWithEditContext::PostType, "type")]
+    fn test_as_mapped_field_name_for_edit_context(
+        #[case] field: SparsePostFieldWithEditContext,
+        #[case] expected_mapped_field_name: &str,
+    ) {
+        assert_eq!(field.as_mapped_field_name(), expected_mapped_field_name);
+    }
+
+    #[rstest]
+    #[case(SparsePostFieldWithEmbedContext::Id, "id")]
+    #[case(SparsePostFieldWithEmbedContext::PostType, "type")]
+    fn test_as_mapped_field_name_for_embed_context(
+        #[case] field: SparsePostFieldWithEmbedContext,
+        #[case] expected_mapped_field_name: &str,
+    ) {
+        assert_eq!(field.as_mapped_field_name(), expected_mapped_field_name);
+    }
+
+    #[rstest]
+    #[case(SparsePostFieldWithViewContext::Id, "id")]
+    #[case(SparsePostFieldWithViewContext::PostType, "type")]
+    fn test_as_mapped_field_name_for_view_context(
+        #[case] field: SparsePostFieldWithViewContext,
+        #[case] expected_mapped_field_name: &str,
+    ) {
+        assert_eq!(field.as_mapped_field_name(), expected_mapped_field_name);
+    }
+
     fn expected_query_pairs_for_post_list_params_with_all_fields() -> String {
         let after = unit_test_example_date_as_query_value("after");
         let modified_after = unit_test_example_date_as_query_value("modified_after");

wp_api/src/request/endpoint.rs

@@ -134,22 +134,6 @@ impl ApiUrlResolver for WpOrgSiteApiUrlResolver {
     }
 }
 
-mod macros {
-    macro_rules! default_sparse_field_implementation_from_field_name {
-        ($ident:ident) => {
-            paste::paste! {
-                impl SparseField for $ident {
-                    fn as_str(&self) -> &str {
-                        self.as_field_name()
-                    }
-                }
-            }
-        };
-    }
-
-    pub(crate) use default_sparse_field_implementation_from_field_name;
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;

wp_api/src/request/endpoint/application_passwords_endpoint.rs

@@ -1,18 +1,18 @@
-use wp_derive_request_builder::WpDerivedRequest;
-
-use crate::SparseField;
-use crate::application_passwords::{
-    ApplicationPasswordCreateParams, ApplicationPasswordDeleteAllResponse,
-    ApplicationPasswordDeleteResponse, ApplicationPasswordUpdateParams, ApplicationPasswordUuid,
-    ApplicationPasswordWithEditContext, ApplicationPasswordWithEmbedContext,
-    ApplicationPasswordWithViewContext, SparseApplicationPasswordFieldWithEditContext,
-    SparseApplicationPasswordFieldWithEmbedContext, SparseApplicationPasswordFieldWithViewContext,
-    SparseApplicationPasswordWithEditContext, SparseApplicationPasswordWithEmbedContext,
-    SparseApplicationPasswordWithViewContext,
-};
-use crate::users::UserId;
-
 use super::{AsNamespace, DerivedRequest, WpNamespace};
+use crate::{
+    application_passwords::{
+        ApplicationPasswordCreateParams, ApplicationPasswordDeleteAllResponse,
+        ApplicationPasswordDeleteResponse, ApplicationPasswordUpdateParams,
+        ApplicationPasswordUuid, ApplicationPasswordWithEditContext,
+        ApplicationPasswordWithEmbedContext, ApplicationPasswordWithViewContext,
+        SparseApplicationPasswordFieldWithEditContext,
+        SparseApplicationPasswordFieldWithEmbedContext,
+        SparseApplicationPasswordFieldWithViewContext, SparseApplicationPasswordWithEditContext,
+        SparseApplicationPasswordWithEmbedContext, SparseApplicationPasswordWithViewContext,
+    },
+    users::UserId,
+};
+use wp_derive_request_builder::WpDerivedRequest;
 
 #[derive(WpDerivedRequest)]
 enum ApplicationPasswordsRequest {
@@ -38,16 +38,6 @@ impl DerivedRequest for ApplicationPasswordsRequest {
     }
 }
 
-super::macros::default_sparse_field_implementation_from_field_name!(
-    SparseApplicationPasswordFieldWithEditContext
-);
-super::macros::default_sparse_field_implementation_from_field_name!(
-    SparseApplicationPasswordFieldWithEmbedContext
-);
-super::macros::default_sparse_field_implementation_from_field_name!(
-    SparseApplicationPasswordFieldWithViewContext
-);
-
 #[cfg(test)]
 mod tests {
     use super::*;

wp_api/src/request/endpoint/categories_endpoint.rs

@@ -1,11 +1,5 @@
 use super::{AsNamespace, DerivedRequest, WpNamespace};
-use crate::{
-    SparseField,
-    categories::{
-        CategoryId, CategoryListParams, SparseCategoryFieldWithEditContext,
-        SparseCategoryFieldWithEmbedContext, SparseCategoryFieldWithViewContext,
-    },
-};
+use crate::categories::{CategoryId, CategoryListParams};
 use wp_derive_request_builder::WpDerivedRequest;
 
 #[derive(WpDerivedRequest)]
@@ -37,22 +31,15 @@ impl DerivedRequest for CategoriesRequest {
     }
 }
 
-super::macros::default_sparse_field_implementation_from_field_name!(
-    SparseCategoryFieldWithEditContext
-);
-super::macros::default_sparse_field_implementation_from_field_name!(
-    SparseCategoryFieldWithEmbedContext
-);
-super::macros::default_sparse_field_implementation_from_field_name!(
-    SparseCategoryFieldWithViewContext
-);
-
 #[cfg(test)]
 mod tests {
     use super::*;
     use crate::{
         WpApiParamOrder,
-        categories::{CategoryId, WpApiParamCategoriesOrderBy},
+        categories::{
+            CategoryId, SparseCategoryFieldWithEditContext, SparseCategoryFieldWithEmbedContext,
+            SparseCategoryFieldWithViewContext, WpApiParamCategoriesOrderBy,
+        },
         generate,
         posts::PostId,
         request::endpoint::{

wp_api/src/request/endpoint/comments_endpoint.rs

@@ -1,8 +1,4 @@
-use crate::SparseField;
-use crate::comments::{
-    CommentId, CommentListParams, CommentUpdateParams, SparseCommentFieldWithEditContext,
-    SparseCommentFieldWithEmbedContext, SparseCommentFieldWithViewContext,
-};
+use crate::comments::{CommentId, CommentListParams, CommentUpdateParams};
 use wp_derive_request_builder::WpDerivedRequest;
 
 use super::{AsNamespace, DerivedRequest, WpNamespace};
@@ -36,41 +32,15 @@ impl DerivedRequest for CommentsRequest {
     }
 }
 
-impl SparseField for SparseCommentFieldWithEditContext {
-    fn as_str(&self) -> &str {
-        match self {
-            Self::CommentType => "type",
-            _ => self.as_field_name(),
-        }
-    }
-}
-
-impl SparseField for SparseCommentFieldWithEmbedContext {
-    fn as_str(&self) -> &str {
-        match self {
-            Self::CommentType => "type",
-            _ => self.as_field_name(),
-        }
-    }
-}
-
-impl SparseField for SparseCommentFieldWithViewContext {
-    fn as_str(&self) -> &str {
-        match self {
-            Self::CommentType => "type",
-            _ => self.as_field_name(),
-        }
-    }
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;
     use crate::{
         UserId, WpApiParamOrder,
         comments::{
             CommentDeleteParams, CommentId, CommentRetrieveParams, CommentStatus, CommentType,
-            WpApiParamCommentsOrderBy,
+            SparseCommentFieldWithEditContext, SparseCommentFieldWithEmbedContext,
+            SparseCommentFieldWithViewContext, WpApiParamCommentsOrderBy,
         },
         generate,
         posts::PostId,

wp_api/src/request/endpoint/media_endpoint.rs

@@ -1,12 +1,7 @@
 use super::{AsNamespace, DerivedRequest, WpEndpointUrl, WpNamespace};
 use crate::{
-    SparseField,
     api_error::WpApiError,
-    media::{
-        MediaCreateParams, MediaId, MediaListParams, MediaUpdateParams, MediaWithEditContext,
-        SparseMediaFieldWithEditContext, SparseMediaFieldWithEmbedContext,
-        SparseMediaFieldWithViewContext,
-    },
+    media::{MediaCreateParams, MediaId, MediaListParams, MediaUpdateParams, MediaWithEditContext},
     request::{
         CONTENT_TYPE_MULTIPART, NetworkRequestAccessor, ParsedResponse, RequestMethod,
         WpNetworkHeaderMap, WpNetworkResponse,
@@ -44,35 +39,6 @@ impl DerivedRequest for MediaRequest {
     }
 }
 
-impl SparseField for SparseMediaFieldWithEditContext {
-    fn as_str(&self) -> &str {
-        match self {
-            Self::PostId => "post",
-            Self::PostType => "type",
-            _ => self.as_field_name(),
-        }
-    }
-}
-
-impl SparseField for SparseMediaFieldWithEmbedContext {
-    fn as_str(&self) -> &str {
-        match self {
-            Self::PostType => "type",
-            _ => self.as_field_name(),
-        }
-    }
-}
-
-impl SparseField for SparseMediaFieldWithViewContext {
-    fn as_str(&self) -> &str {
-        match self {
-            Self::PostId => "post",
-            Self::PostType => "type",
-            _ => self.as_field_name(),
-        }
-    }
-}
-
 impl MediaRequestEndpoint {
     pub fn create(&self) -> crate::request::endpoint::ApiEndpointUrl {
         Arc::unwrap_or_clone(self.api_url_resolver.resolve(
@@ -239,7 +205,10 @@ mod tests {
     use super::*;
     use crate::{
         UserId, WpApiParamOrder, generate,
-        media::{MediaId, MediaStatus, MediaTypeParam},
+        media::{
+            MediaId, MediaStatus, MediaTypeParam, SparseMediaFieldWithEditContext,
+            SparseMediaFieldWithEmbedContext, SparseMediaFieldWithViewContext,
+        },
         posts::{PostId, WpApiParamPostsOrderBy, WpApiParamPostsSearchColumn},
         request::endpoint::{
             ApiUrlResolver,