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

.github/workflows/deepwell.yaml

@@ -111,7 +111,10 @@ jobs:
         env:
           DEEPWELL_RUNTIME_ACTION: run-seeder
 
-      - name: Test
+      - name: Unit Tests (deepwell-relation-impl-derive)
+        run: cd deepwell/relation-impl-derive && cargo test
+
+      - name: Integration Tests
         run: cd deepwell && cargo test --all-features -- --nocapture --test-threads 1
 
       - name: Generate Coverage

deepwell/Cargo.toml

@@ -8,7 +8,7 @@ keywords = ["wikijump", "api", "backend", "wiki"]
 categories = ["asynchronous", "database", "web-programming::http-server"]
 exclude = [".gitignore", ".editorconfig"]
 
-version = "2026.7.22"
+version = "2026.7.27"
 authors = ["Emmie Smith <emmie.maeda@gmail.com>"]
 edition = "2024"
 
@@ -71,6 +71,9 @@ wikidot-normalize = "0.12"
 wikidot-path = "0.6"
 arrayvec = "0.7.6"
 
+# Local crates
+deepwell-relation-impl-derive = { path = "relation-impl-derive" }
+
 [dev-dependencies]
 maplit = "1"
 pretty_assertions = "1"

deepwell/relation-impl-derive/Cargo.toml

@@ -0,0 +1,19 @@
+[package]
+name = "deepwell-relation-impl-derive"
+description = "Procedural macro to generate boilerplate for relation methods"
+repository = "https://github.com/scpwiki/wikijump/tree/develop/deepwell/relation-impl-derive"
+
+version = "1.1.0"
+authors = ["Emmie Smith <emmie.maeda@gmail.com>"]
+edition = "2024"
+
+[lib]
+proc-macro = true
+
+[dependencies]
+syn = "3"
+quote = "1"
+proc-macro2 = "1"
+
+[lints.rust]
+unsafe_code = "forbid"

deepwell/relation-impl-derive/README.md

@@ -0,0 +1,7 @@
+# deepwell-relation-impl-derive
+
+This helper crate exists to store the procedural macro for generating methods and structures for relations (see `RelationService`). The [old `impl_relation!` macro](https://github.com/scpwiki/wikijump/blob/0a26522e50e0a2bdc0abddfe6338e6a882d24b74/deepwell/src/services/relation/macros.rs#L23) was defined via `macro_rules!`, but as it grew more complicated and took more options, it became increasingly cumbersome to maintain.
+
+This proc macro performs the same tasks as the old macro, but with better syntax, more options, and avoiding automatable work (e.g. converting between `PascalCase` and `snake_case`).
+
+See #3039 for further information.

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

@@ -0,0 +1,35 @@
+//! Helper utilities in processing different naming cases.
+
+/// Convert `PascalCase` to `snake_case`.
+pub fn pascal_to_snake_case(value: &str) -> String {
+    let mut output = String::new();
+    for (i, ch) in value.char_indices() {
+        if i > 0 && ch.is_uppercase() {
+            output.push('_');
+        }
+        output.push(ch.to_ascii_lowercase());
+    }
+    output
+}
+
+#[test]
+fn test_pascal_to_snake_case() {
+    macro_rules! test {
+        ($pascal_case:expr, $snake_case:expr $(,)?) => {{
+            let actual_snake_case = pascal_to_snake_case($pascal_case);
+            let expected_snake_case = $snake_case;
+            assert_eq!(
+                actual_snake_case, expected_snake_case,
+                "actual snake_case conversion doesn't match expected",
+            );
+        }};
+    }
+
+    test!("", "");
+    test!("Foo", "foo");
+    test!("FooBar", "foo_bar");
+    test!(
+        "AVeryLongNameWithManyParts",
+        "a_very_long_name_with_many_parts",
+    );
+}