Add support for PostgreSQL 12

PostgreSQL 12 brings changes to FunctionCallInfoData (the way arguments
are passed to functions).

Upstream commit:
postgres/postgres@a9c35cf

pg-extend/Cargo.toml

@@ -22,6 +22,7 @@ fdw = []
 postgres-9 = ["fdw"]
 postgres-10 = ["fdw"]
 postgres-11 = []
+postgres-12 = []
 
 [dependencies]
 

pg-extend/build.rs

@@ -60,7 +60,7 @@ fn main() {
         .expect("Couldn't write bindings!");
 
     let feature_version = get_postgres_feature_version(pg_include);
-    println!("cargo:rustc-cfg=feature=\"{}\"", feature_version)
+    println!("cargo:rustc-cfg=feature=\"{}\"", feature_version);
 }
 
 fn include_dir() -> Result<String, env::VarError> {
@@ -122,6 +122,7 @@ fn get_postgres_feature_version(pg_include: String) -> &'static str {
         ["9", _] => "postgres-9",
         ["10"] => "postgres-10",
         ["11"] => "postgres-11",
+        ["12"] => "postgres-12",
         val => panic!("unknown Postgres version {:?}", val),
     }
 }

pg-extend/src/lib.rs

@@ -60,21 +60,43 @@ macro_rules! pg_magic {
     };
 }
 
-/// Returns the slice of Datums, and a parallel slice which specifies if the Datum passed in is (SQL) NULL
+#[cfg(feature = "postgres-12")]
+type FunctionCallInfoData = pg_sys::FunctionCallInfoBaseData;
+#[cfg(not(feature = "postgres-12"))]
+type FunctionCallInfoData = pg_sys::FunctionCallInfoData;
+
+/// Returns an iterator of argument Datums
 pub fn get_args<'a>(
-    func_call_info: &'a pg_sys::FunctionCallInfoData,
-) -> (
-    impl 'a + Iterator<Item = &pg_sys::Datum>,
-    impl 'a + Iterator<Item = pg_bool::Bool>,
-) {
+    func_call_info: &'a FunctionCallInfoData,
+) -> impl 'a + Iterator<Item = Option<pg_sys::Datum>> {
     let num_args = func_call_info.nargs as usize;
 
-    let args = func_call_info.arg[..num_args].iter();
-    let args_null = func_call_info.argnull[..num_args]
+    // PostgreSQL 12+: Convert from pg_sys::NullableDatum
+    #[cfg(feature = "postgres-12")]
+    return unsafe { func_call_info.args.as_slice(num_args) }
         .iter()
-        .map(|b| pg_bool::Bool::from(*b));
-
-    (args, args_null)
+        .map(|nullable| {
+            if nullable.isnull {
+                None
+            } else {
+                Some(nullable.value)
+            }
+        });
+
+    // Older versions store two separate arrays for 'isnull' and datums
+    #[cfg(not(feature = "postgres-12"))]
+    return {
+        let args = &func_call_info.arg[..num_args];
+        let args_null = &func_call_info.argnull[..num_args];
+
+        args.iter().zip(args_null.iter()).map(|(value, isnull)| {
+            if pg_bool::Bool::from(*isnull).into() {
+                None
+            } else {
+                Some(*value)
+            }
+        })
+    };
 }
 
 /// Information for a longjmp
@@ -126,7 +148,8 @@ pub fn register_panic_handler() {
 pub(crate) unsafe fn guard_pg<R, F: FnOnce() -> R>(f: F) -> R {
     // setup the check protection
     let original_exception_stack: *mut pg_sys::sigjmp_buf = pg_sys::PG_exception_stack;
-    let mut local_exception_stack: mem::MaybeUninit<pg_sys::sigjmp_buf> = mem::MaybeUninit::uninit();
+    let mut local_exception_stack: mem::MaybeUninit<pg_sys::sigjmp_buf> =
+        mem::MaybeUninit::uninit();
     let jumped = pg_sys::sigsetjmp(
         // grab a mutable reference, cast to a mutabl pointr, then case to the expected erased pointer type
         local_exception_stack.as_mut_ptr() as *mut pg_sys::sigjmp_buf as *mut _,

pg-extend/src/pg_datum.rs

@@ -35,6 +35,14 @@ impl<'mc> PgDatum<'mc> {
         PgDatum(datum, PhantomData)
     }
 
+    /// Returns a new PgDatum wrapper if you already have Option<Datum>
+    pub unsafe fn from_option(
+        _memory_context: &'mc PgAllocator,
+        datum: Option<Datum>,
+    ) -> PgDatum<'mc> {
+        PgDatum(datum, PhantomData)
+    }
+
     /// Return true if this Datum is None
     ///
     /// # Notes

pg-extend/src/pg_fdw.rs

@@ -8,7 +8,7 @@
 
 // FDW on PostgreSQL 11+ is not supported. :(
 // If anyone tries to enable "fdw" feature with newer Postgres, throw error.
-#[cfg(feature = "postgres-11")]
+#[cfg(any(feature = "postgres-11", feature = "postgres-12"))]
 compile_error!("pg-extend-rs does not support FDW on PostgreSQL 11 or newer. See https://github.com/bluejekyll/pg-extend-rs/issues/49");
 
 use std::boxed::Box;

pg-extern-attr/src/lib.rs

@@ -10,11 +10,9 @@
 extern crate proc_macro;
 extern crate proc_macro2;
 #[macro_use]
-extern crate syn;
-#[macro_use]
 extern crate quote;
-
-mod lifetime;
+#[macro_use]
+extern crate syn;
 
 use proc_macro2::{Ident, Span, TokenStream};
 use quote::ToTokens;
@@ -23,6 +21,8 @@ use syn::spanned::Spanned;
 use syn::token::Comma;
 use syn::Type;
 
+mod lifetime;
+
 /// A type that represents that PgAllocator is an argument to the Rust function.
 type HasPgAllocatorArg = bool;
 
@@ -104,14 +104,11 @@ fn extract_arg_data(arg_types: &[Type]) -> (TokenStream, HasPgAllocatorArg) {
         let arg_error = format!("unsupported function argument type for {}", arg_name);
 
         let get_arg = quote_spanned!( arg_type.span()=>
+            let datum = args.next().expect("wrong number of args passed into get_args for args?");
             let #arg_name: #arg_type = unsafe {
                 pg_extend::pg_datum::TryFromPgDatum::try_from(
                     &memory_context,
-                    pg_extend::pg_datum::PgDatum::from_raw(
-                        &memory_context,
-                        *args.next().expect("wrong number of args passed into get_args for args?"),
-                        args_null.next().expect("wrong number of args passed into get_args for args_null?")
-                    ),
+                    pg_extend::pg_datum::PgDatum::from_option(&memory_context, datum),
                 )
                 .expect(#arg_error)
             };
@@ -337,7 +334,7 @@ fn impl_info_for_fn(item: &syn::Item) -> TokenStream {
             // All params will be in the "current" memory context at the call-site
             let memory_context = PgAllocator::current_context();
 
-            let func_info: &mut pg_extend::pg_sys::FunctionCallInfoData = unsafe {
+            let func_info = unsafe {
                 func_call_info
                     .as_mut()
                     .expect("func_call_info was unexpectedly NULL")
@@ -346,7 +343,7 @@ fn impl_info_for_fn(item: &syn::Item) -> TokenStream {
             // guard the Postgres process against the panic, and give us an oportunity to cleanup
             let panic_result = panic::catch_unwind(|| {
                 // extract the argument list
-                let (mut args, mut args_null) = pg_extend::get_args(func_info);
+                let mut args = pg_extend::get_args(func_info);
 
                 // arbitrary Datum conversions occur here, and could panic
                 //   so this is inside the catch unwind