Factor out finfo_tokens (#1673)

An initial toehold on refactoring work to partially unify wrapper-fn
expansions in their implementations, especially where it is
correctness-relevant.

pgrx-sql-entity-graph/src/finfo.rs

@@ -0,0 +1,19 @@
+use quote::{format_ident, quote};
+use syn::{self, ItemFn};
+
+/// Generate the Postgres fn info record
+///
+/// Equivalent to PG_FUNCTION_INFO_V1, Postgres will sprintf the fn ident, then `dlsym(so, expected_name)`,
+/// so it is important to pass exactly the ident that you want to have the record associated with!
+pub fn finfo_v1_tokens(ident: proc_macro2::Ident) -> syn::Result<ItemFn> {
+    let finfo_name = format_ident!("pg_finfo_{ident}");
+    let tokens = quote! {
+        #[no_mangle]
+        #[doc(hidden)]
+        pub extern "C" fn #finfo_name() -> &'static ::pgrx::pg_sys::Pg_finfo_record {
+            const V1_API: ::pgrx::pg_sys::Pg_finfo_record = ::pgrx::pg_sys::Pg_finfo_record { api_version: 1 };
+            &V1_API
+        }
+    };
+    syn::parse2(tokens)
+}

pgrx-sql-entity-graph/src/lib.rs

@@ -57,6 +57,7 @@ pub(crate) mod control_file;
 pub(crate) mod enrich;
 pub(crate) mod extension_sql;
 pub(crate) mod extern_args;
+pub(crate) mod finfo;
 #[macro_use]
 pub(crate) mod fmt;
 pub mod lifetimes;

pgrx-sql-entity-graph/src/pg_extern/mod.rs

@@ -28,6 +28,7 @@ pub use cast::PgCast;
 pub use operator::PgOperator;
 pub use returning::NameMacro;
 
+use crate::finfo::finfo_v1_tokens;
 use crate::fmt::ErrHarder;
 use crate::ToSqlConfig;
 pub(crate) use attribute::Attribute;
@@ -375,19 +376,7 @@ impl PgExtern {
         }
     }
 
-    fn finfo_tokens(&self) -> TokenStream2 {
-        let finfo_name = format_ident!("pg_finfo_{}_wrapper", self.func.sig.ident);
-        quote_spanned! { self.func.sig.span() =>
-            #[no_mangle]
-            #[doc(hidden)]
-            pub extern "C" fn #finfo_name() -> &'static ::pgrx::pg_sys::Pg_finfo_record {
-                const V1_API: ::pgrx::pg_sys::Pg_finfo_record = ::pgrx::pg_sys::Pg_finfo_record { api_version: 1 };
-                &V1_API
-            }
-        }
-    }
-
-    pub fn wrapper_func(&self) -> TokenStream2 {
+    pub fn wrapper_func(&self) -> Result<syn::ItemFn, syn::Error> {
         let func_name = &self.func.sig.ident;
         let func_name_wrapper = format_ident!("{}_wrapper", &self.func.sig.ident);
         let func_generics = &self.func.sig.generics;
@@ -456,15 +445,16 @@ impl PgExtern {
         let extern_c_wrapper =
             |span, returns_datum: bool, wrapped_contents: proc_macro2::TokenStream| {
                 let return_ty = returns_datum.then(|| quote! { -> ::pgrx::pg_sys::Datum });
-                quote_spanned! { span=>
+                let tokens = quote_spanned! { span=>
                     #[no_mangle]
                     #[doc(hidden)]
                     #unused_lifetimes
                     #[::pgrx::pgrx_macros::pg_guard]
                     pub unsafe extern "C" fn #func_name_wrapper #func_generics(#fcinfo_ident: ::pgrx::pg_sys::FunctionCallInfo) #return_ty {
                         #wrapped_contents
                     }
-                }
+                };
+                syn::parse2(tokens)
             };
 
         match &self.returns {
@@ -600,8 +590,8 @@ impl ToEntityGraphTokens for PgExtern {
 impl ToRustCodeTokens for PgExtern {
     fn to_rust_code_tokens(&self) -> TokenStream2 {
         let original_func = &self.func;
-        let wrapper_func = self.wrapper_func();
-        let finfo_tokens = self.finfo_tokens();
+        let wrapper_func = self.wrapper_func().unwrap();
+        let finfo_tokens = finfo_v1_tokens(wrapper_func.sig.ident.clone()).unwrap();
 
         quote_spanned! { self.func.sig.span() =>
             #original_func

pgrx-sql-entity-graph/src/pg_trigger/mod.rs

@@ -19,6 +19,7 @@ pub mod attribute;
 pub mod entity;
 
 use crate::enrich::{ToEntityGraphTokens, ToRustCodeTokens};
+use crate::finfo::finfo_v1_tokens;
 use crate::{CodeEnrichment, ToSqlConfig};
 use attribute::PgTriggerAttribute;
 use proc_macro2::TokenStream as TokenStream2;
@@ -101,19 +102,6 @@ impl PgTrigger {
         };
         syn::parse2(tokens)
     }
-
-    pub fn finfo_tokens(&self) -> Result<ItemFn, syn::Error> {
-        let finfo_name = format_ident!("pg_finfo_{}_wrapper", self.func.sig.ident);
-        let tokens = quote! {
-            #[no_mangle]
-            #[doc(hidden)]
-            pub extern "C" fn #finfo_name() -> &'static ::pgrx::pg_sys::Pg_finfo_record {
-                const V1_API: ::pgrx::pg_sys::Pg_finfo_record = ::pgrx::pg_sys::Pg_finfo_record { api_version: 1 };
-                &V1_API
-            }
-        };
-        syn::parse2(tokens)
-    }
 }
 
 impl ToEntityGraphTokens for PgTrigger {
@@ -148,8 +136,8 @@ impl ToEntityGraphTokens for PgTrigger {
 
 impl ToRustCodeTokens for PgTrigger {
     fn to_rust_code_tokens(&self) -> TokenStream2 {
-        let wrapper_func = self.wrapper_tokens().expect("Generating wrappper function for trigger");
-        let finfo_func = self.finfo_tokens().expect("Generating finfo function for trigger");
+        let wrapper_func = self.wrapper_tokens().expect("Generating wrapper function for trigger");
+        let finfo_func = finfo_v1_tokens(wrapper_func.sig.ident.clone()).unwrap();
         let func = &self.func;
 
         quote! {