[WJ-1168] Add proc macro for generating relation structs and methods by emmiegit · Pull Request #3039 · scpwiki/wikijump

emmiegit · 2026-07-28T08:08:49Z

Up to this point, we used a normal macro_rules! macro to generate the code for relations. This had a few problems, such as it being cumbersome to disable generation of creation structs or methods, and the inability to exclude metadata as a field if it wasn't used for that relation (e.g. is ()).

With the new requirement to permit disabling remove_*() method generation as well, I decided that the code was getting too complicated and it was time to use a procedural macro to generate the code instead. This allows for specifying a relation in a more readable syntax, as well as handling some niceties for us (such as doing the PascalCase to snake_case conversion for fields automatically).

The arguments accepted are as follows:

impl_relation! {
    // Required. Name of relation in PascalCase.
    name => NameOfRelation,

    // Required. Name and object type of "dest".
    dest => destination_field: Page,

    // Required. Name and object type of "from".
    from => from_field: User,

    // Optional. Associated data type. Default is ().
    data => RelationExtraData,

    // Optional. How to generate the creation code for the relation. Default is true.
    //
    // Values are:
    //  * true   - Generate public struct and public creation method.
    //  * false  - Generate public struct and private "inner" creation method.
    //             Public creation method must be defined by the programmer.
    //  * extern - Generate neither a struct nor creation method.
    //             Both must be defined by the programmer.
    create_fn => false,

    // Optional. How to generate the removal code for the relation. Default is true.
    // Same values as above.
    remove_fn => true,
}

With this done, I changed the site member and ban relations to add the audit logging, and did some refactoring to make the struct handling in endpoints/ consistent.

Naturally, I also deleted the old macro definition.

First fully-working version, emits compiling code for all relations.

Now using our new procedural macro! Very exciting.

codecov · 2026-07-28T09:47:39Z

Codecov Report

❌ Patch coverage is 52.28758% with 73 lines in your changes missing coverage. Please review.
✅ Project coverage is 26.54%. Comparing base (a76ba79) to head (c2be791).
⚠️ Report is 2 commits behind head on develop.

Files with missing lines	Patch %	Lines
deepwell/src/services/audit/structs.rs	18.75%	13 Missing ⚠️
deepwell/src/services/relation/user_block.rs	0.00%	11 Missing ⚠️
deepwell/src/services/relation/user_bot_owner.rs	0.00%	11 Missing ⚠️
deepwell/src/services/relation/user_follow.rs	0.00%	10 Missing ⚠️
deepwell/relation-impl-derive/src/types.rs	0.00%	6 Missing ⚠️
deepwell/src/endpoints/site_ban.rs	66.66%	6 Missing ⚠️
deepwell/relation-impl-derive/src/util.rs	0.00%	4 Missing ⚠️
deepwell/src/endpoints/site_member.rs	33.33%	4 Missing ⚠️
deepwell/src/services/relation/page_star.rs	0.00%	3 Missing ⚠️
deepwell/src/services/relation/page_watch.rs	0.00%	3 Missing ⚠️
... and 1 more

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #3039      +/-   ##
===========================================
- Coverage    26.62%   26.54%   -0.09%     
===========================================
  Files          198      201       +3     
  Lines        13451    13470      +19     
===========================================
- Hits          3582     3576       -6     
- Misses        9869     9894      +25

Files with missing lines	Coverage Δ
deepwell/src/services/relation/mod.rs	`63.86% <ø> (ø)`
deepwell/src/services/relation/site_ban.rs	`93.04% <100.00%> (+0.45%)`	⬆️
deepwell/src/services/relation/site_user.rs	`35.61% <100.00%> (+7.92%)`	⬆️
deepwell/src/services/site/service.rs	`37.44% <ø> (ø)`
deepwell/src/services/relation/site_member.rs	`95.83% <95.12%> (-4.17%)`	⬇️
deepwell/src/services/relation/page_star.rs	`0.00% <0.00%> (ø)`
deepwell/src/services/relation/page_watch.rs	`0.00% <0.00%> (ø)`
deepwell/relation-impl-derive/src/util.rs	`0.00% <0.00%> (ø)`
deepwell/src/endpoints/site_member.rs	`51.61% <33.33%> (-3.95%)`	⬇️
deepwell/relation-impl-derive/src/types.rs	`0.00% <0.00%> (ø)`
... and 5 more

... and 5 files with indirect coverage changes

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WackDog · 2026-07-28T12:51:58Z

+    dest => bot_user: User,
+    from => owner_user: User,
+    data => UserBotMetadata,
+    create_fn => false,


Should this be create_fn => extern rather than false? The previous invocation used NO_CREATE_IMPL_OR_STRUCT and the parser test also models UserBotOwner using extern . My understanding is that false still generates the public creation struct, whereas extern generates neither the struct or method.

When it's false, it creates a private creation method and struct, which is used in the custom public creation method. But you're right, there isn't a way to disable public struct creation except with extern; we need an option for "create private/inner, but nothing public".

I've updated the PR to add separate settings for "create private/inner struct+method only" and "create private/inner struct+method, and a public struct for convenience".

WackDog · 2026-07-28T13:02:02Z

+use crate::types::{GenerateMethod, RelationObjectType};
+use syn::Type;
+
+#[test]


Non-blocking: would it be useful to add compile tests for the generated output, perhaps with trybuild?

Hmm, that's worth considering. I originally thoguht about doing tests (in the proc macro crate) for parsing and expansion, but then I thought it would be easier to just ensure deepwell itself built rather than setting up a duplicate system for testing. But maybe trybuild is closer to what I want here.

If I do implement this, it would be in a follow-up PR.

More readable.

WackDog · 2026-07-31T16:51:47Z

+    } else {
+        quote! {}
+    };


Does remove_fn => private_only currently leave the generated method without its input struct?
For PrivateWithoutStruct, generate_pub_struct is false, so this branch emits no Remove{Relation} struct. However, the generated remove_*_inner() method below still destructures Remove{Relation}. Should this mode generate a private removal struct, or should private_only not be supported for remove_fn?

WackDog · 2026-07-31T16:55:04Z

+                }
+
+                // Designate how the remove method should be generated
+                // This key is optional, default is "true".


should this say the default is public, with the example using remove_fn => public? The parser doesn't accept true anymore

emmiegit requested review from WackDog and Zokhoi July 28, 2026 08:08

emmiegit self-assigned this Jul 28, 2026

emmiegit force-pushed the WJ-1168-site-ban-macro branch 4 times, most recently from a397e57 to 503186b Compare July 28, 2026 09:05

emmiegit marked this pull request as ready for review July 28, 2026 09:09

emmiegit force-pushed the WJ-1168-site-ban-macro branch from 503186b to 2911363 Compare July 28, 2026 09:25

emmiegit added 21 commits July 28, 2026 05:28

Create stub proc macro crate for deepwell.

7e2c8d3

Add stub in proc macro subcrate.

2aa55b0

First compiling version of macro crate.

a3f1cf1

Create make_ident() helper.

28300fa

Add dest / from parsing.

f57d71d

Add data type to macro.

f2ca29c

Fix loop condition.

97004a2

Ensure required field and build output.

85263de

Run rustfmt.

25309eb

Add lines between each argument.

dd6f13a

Error if field is set multiple times.

4f0829f

Add process_type for handling () -> null.

1cad13c

Add data_type and method arguments.

bfc022e

Remove root TODO.

829fc40

Bump macro crate version to 0.0.2

4147596

Add define_struct argument to macro.

e01897f

Suppress some warnings.

9924ddd

Bump macro crate version to 0.0.3

2b50ac5

Set up testing.

0155c8c

Intake commas after each key and value.

b41aec5

Perform lookahead in GenerateMethod::parse().

6fec51d

emmiegit added 7 commits July 28, 2026 05:28

Add rustdocs for proc macro.

31a4d26

Link this PR in the proc macro README.

efd7aba

Add proc macro testing to CI.

1444e1d

Forbid unsafe code in proc macro.

7b170ff

Bump macro crate version to 1.0.0

353386e

First fully-working version, emits compiling code for all relations.

Remove old relation codegen macro.

815c530

Now using our new procedural macro! Very exciting.

Fix integration tests.

747febf

emmiegit force-pushed the WJ-1168-site-ban-macro branch from 2911363 to 7fbe212 Compare July 28, 2026 09:28

emmiegit enabled auto-merge July 28, 2026 10:26

WackDog reviewed Jul 28, 2026

View reviewed changes

Comment thread deepwell/relation-impl-derive/src/case.rs

WackDog reviewed Jul 28, 2026

View reviewed changes

Comment thread deepwell/src/services/relation/site_member.rs

emmiegit disabled auto-merge July 28, 2026 13:43

emmiegit added 4 commits July 30, 2026 01:24

Move latest_audit_event() to new helper module.

9f0d05f

Handle unused helper function warnings.

d57b1b2

Add assertions for site_member.join event.

fbf5fb4

Add assertions for site_member.remove event.

e8240d7

emmiegit force-pushed the WJ-1168-site-ban-macro branch from 0f86650 to 4fbd1a8 Compare July 30, 2026 05:31

emmiegit added 7 commits July 30, 2026 02:23

Add PrivateWithStruct variant to proc macro.

c62ec93

Add GenerateMethodSettings to enable Private vs PrivateWithStruct.

eabb6e7

Update tests with new variants.

40a8bde

Change to identifier-based GenerateMethod values.

81cd352

More readable.

Bump macro crate version to 1.1.0

d54d238

Convert to new GenerateMethod specifiers.

af88cd4

Bump deepwell version to v2026.7.27

c2be791

emmiegit force-pushed the WJ-1168-site-ban-macro branch from 4fbd1a8 to c2be791 Compare July 30, 2026 06:23

WackDog reviewed Jul 31, 2026

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[WJ-1168] Add proc macro for generating relation structs and methods - #3039

[WJ-1168] Add proc macro for generating relation structs and methods#3039
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