feat: Allow variants and records to be ignored by additional_derives

crates/guest-rust/macro/src/lib.rs

@@ -115,6 +115,10 @@ impl Parse for Config {
                             .map(|p| p.into_token_stream().to_string())
                             .collect()
                     }
+                    Opt::AdditionalDerivesIgnore(list) => {
+                        opts.additional_derive_ignore =
+                            list.into_iter().map(|i| i.value()).collect()
+                    }
                     Opt::With(with) => opts.with.extend(with),
                     Opt::GenerateAll => {
                         opts.generate_all = true;
@@ -323,6 +327,7 @@ mod kw {
     syn::custom_keyword!(stubs);
     syn::custom_keyword!(export_prefix);
     syn::custom_keyword!(additional_derives);
+    syn::custom_keyword!(additional_derives_ignore);
     syn::custom_keyword!(with);
     syn::custom_keyword!(generate_all);
     syn::custom_keyword!(type_section_suffix);
@@ -383,6 +388,7 @@ enum Opt {
     ExportPrefix(syn::LitStr),
     // Parse as paths so we can take the concrete types/macro names rather than raw strings
     AdditionalDerives(Vec<syn::Path>),
+    AdditionalDerivesIgnore(Vec<syn::LitStr>),
     With(HashMap<String, WithOption>),
     GenerateAll,
     TypeSectionSuffix(syn::LitStr),
@@ -496,6 +502,13 @@ impl Parse for Opt {
             syn::bracketed!(contents in input);
             let list = Punctuated::<_, Token![,]>::parse_terminated(&contents)?;
             Ok(Opt::AdditionalDerives(list.iter().cloned().collect()))
+        } else if l.peek(kw::additional_derives_ignore) {
+            input.parse::<kw::additional_derives_ignore>()?;
+            input.parse::<Token![:]>()?;
+            let contents;
+            syn::bracketed!(contents in input);
+            let list = Punctuated::<_, Token![,]>::parse_terminated(&contents)?;
+            Ok(Opt::AdditionalDerivesIgnore(list.iter().cloned().collect()))
         } else if l.peek(kw::with) {
             input.parse::<kw::with>()?;
             input.parse::<Token![:]>()?;

crates/rust/src/interface.rs

@@ -1821,7 +1821,15 @@ pub mod vtable{ordinal} {{
             .collect();
         for (name, mode) in self.modes_of(id) {
             self.rustdoc(docs);
-            let mut derives = additional_derives.clone();
+            let mut derives = BTreeSet::new();
+            if !self
+                .gen
+                .opts
+                .additional_derive_ignore
+                .contains(&name.to_kebab_case())
+            {
+                derives.extend(additional_derives.clone());
+            }
             if info.is_copy() {
                 self.push_str("#[repr(C)]\n");
                 derives.extend(["Copy", "Clone"].into_iter().map(|s| s.to_string()));
@@ -1924,7 +1932,15 @@ pub mod vtable{ordinal} {{
             .collect();
         for (name, mode) in self.modes_of(id) {
             self.rustdoc(docs);
-            let mut derives = additional_derives.clone();
+            let mut derives = BTreeSet::new();
+            if !self
+                .gen
+                .opts
+                .additional_derive_ignore
+                .contains(&name.to_kebab_case())
+            {
+                derives.extend(additional_derives.clone());
+            }
             if info.is_copy() {
                 derives.extend(["Copy", "Clone"].into_iter().map(|s| s.to_string()));
             } else if info.is_clone() {
@@ -2072,13 +2088,15 @@ pub mod vtable{ordinal} {{
         self.int_repr(enum_.tag());
         self.push_str(")]\n");
         // We use a BTree set to make sure we don't have any duplicates and a stable order
-        let mut derives: BTreeSet<String> = self
+        let mut derives: BTreeSet<String> = BTreeSet::new();
+        if !self
             .gen
             .opts
-            .additional_derive_attributes
-            .iter()
-            .cloned()
-            .collect();
+            .additional_derive_ignore
+            .contains(&name.to_kebab_case())
+        {
+            derives.extend(self.gen.opts.additional_derive_attributes.to_vec());
+        }
         derives.extend(
             ["Clone", "Copy", "PartialEq", "Eq", "PartialOrd", "Ord"]
                 .into_iter()

crates/rust/src/lib.rs

@@ -248,6 +248,15 @@ pub struct Opts {
     #[cfg_attr(feature = "clap", arg(long = "additional_derive_attribute", short = 'd', default_values_t = Vec::<String>::new()))]
     pub additional_derive_attributes: Vec<String>,
 
+    /// Variants and records to ignore when applying additional derive attributes.
+    ///
+    /// These names are specified as they are listed in the wit file, i.e. in kebab case.
+    /// This feature allows some variants and records to use types for which adding traits will cause
+    /// compilation to fail, such as serde::Deserialize on wasi:io/streams.
+    ///
+    #[cfg_attr(feature = "clap", arg(long = "additional_derive_ignore", default_values_t = Vec::<String>::new()))]
+    pub additional_derive_ignore: Vec<String>,
+
     /// Remapping of wit interface and type names to Rust module names and types.
     ///
     /// Argument must be of the form `k=v` and this option can be passed
@@ -1030,6 +1039,13 @@ impl WorldGenerator for RustWasm {
                 self.opts.additional_derive_attributes
             );
         }
+        if !self.opts.additional_derive_ignore.is_empty() {
+            uwriteln!(
+                self.src_preamble,
+                "//   * additional derives ignored {:?}",
+                self.opts.additional_derive_ignore
+            );
+        }
         for (k, v) in self.opts.with.iter() {
             uwriteln!(self.src_preamble, "//   * with {k:?} = {v}");
         }

crates/rust/tests/codegen.rs

@@ -388,13 +388,26 @@ mod custom_derives {
         inline: "
             package my:inline;
 
+            interface blag {
+                resource input-stream {
+                    read: func(len: u64) -> list<u8>;
+                }
+            }
+
             interface blah {
+                use blag.{input-stream};
                 record foo {
                     field1: string,
                     field2: list<u32>
                 }
 
                 bar: func(cool: foo);
+
+                variant ignoreme {
+                    stream-type(input-stream),
+                }
+
+                barry: func(warm: ignoreme);
             }
 
             world baz {
@@ -405,9 +418,10 @@ mod custom_derives {
         // Clone is included by default almost everywhere, so include it here to make sure it
         // doesn't conflict
         additional_derives: [serde::Serialize, serde::Deserialize, Hash, Clone, PartialEq, Eq],
+        additional_derives_ignore: ["ignoreme"],
     });
 
-    use exports::my::inline::blah::Foo;
+    use exports::my::inline::blah::{Foo, Ignoreme};
 
     struct Component;
 
@@ -423,6 +437,11 @@ mod custom_derives {
             // compilation will fail here
             let _ = serde_json::to_string(&cool);
         }
+
+        fn barry(warm: Ignoreme) {
+            // Compilation would fail if serde::Deserialize was applied to Ignoreme
+            let _ = warm;
+        }
     }
 
     export!(Component);