fix(code): support for unsigned on nullable fields (#67)

The unsigned support introduced in
b41e14a#r125954859 was incomplete as it
did not cover the case where the unsigned field also is nullable. This
change updates the code to convert the base type to unsigned in both
cases.

Fixes #65

src/code.rs

@@ -149,13 +149,16 @@ impl<'a> Struct<'a> {
             })
             .map(|c| {
                 let name = c.name.to_string();
-                let base_type = if c.is_nullable {
-                    format!("Option<{}>", c.ty)
-                } else if c.is_unsigned {
+                let base_type = if c.is_unsigned {
                     c.ty.replace('i', "u")
                 } else {
                     c.ty.clone()
                 };
+                let base_type = if c.is_nullable {
+                    format!("Option<{}>", base_type)
+                } else {
+                    base_type
+                };
                 let mut is_optional = false;
 
                 let is_pk = self

test/simple_table/models/todos/generated.rs

@@ -13,6 +13,7 @@ type Connection = diesel::r2d2::PooledConnection<diesel::r2d2::ConnectionManager
 pub struct Todo {
     pub id: i32,
     pub unsigned: u32,
+    pub unsigned_nullable: Option<u32>,
     pub text: String,
     pub completed: bool,
     pub type_: String,
@@ -24,6 +25,7 @@ pub struct Todo {
 #[diesel(table_name=todos)]
 pub struct CreateTodo {
     pub unsigned: u32,
+    pub unsigned_nullable: Option<u32>,
     pub text: String,
     pub completed: bool,
     pub type_: String,
@@ -33,6 +35,7 @@ pub struct CreateTodo {
 #[diesel(table_name=todos)]
 pub struct UpdateTodo {
     pub unsigned: Option<u32>,
+    pub unsigned_nullable: Option<Option<u32>>,
     pub text: Option<String>,
     pub completed: Option<bool>,
     pub type_: Option<String>,

test/simple_table/schema.rs

@@ -2,6 +2,7 @@ diesel::table! {
     todos (id) {
         id -> Int4,
         unsigned -> Unsigned<Integer>,
+        unsigned_nullable -> Nullable<Unsigned<Integer>>,
         text -> Text,
         completed -> Bool,
         #[sql_name = "type"]