Add an internal __skip_visibility option to changeset_for

Right now we can't inline test structs that want to test
`#[changeset_for]` into the test itself, as Rust will complain that
privacy has no meaning there (which is true). This should never really
affect code outside of our own test suite, so it's not being added to
the public API.

diesel_codegen/src/update.rs

@@ -1,9 +1,10 @@
 use aster;
 use syntax::ast::{self, MetaItem, TyPath};
+use syntax::attr::AttrMetaMethods;
 use syntax::codemap::Span;
 use syntax::ext::base::{Annotatable, ExtCtxt};
 use syntax::ptr::P;
-use syntax::parse::token::{InternedString, intern_and_get_ident};
+use syntax::parse::token::{InternedString, intern_and_get_ident, str_to_ident};
 
 use attr::Attr;
 use model::Model;
@@ -18,9 +19,9 @@ pub fn expand_changeset_for(
     let builder = aster::AstBuilder::new().span(span);
 
     if let Some(model) = Model::from_annotable(cx, &builder, annotatable) {
-        let table = changeset_tables(cx, meta_item).unwrap();
-        push(Annotatable::Item(changeset_impl(cx, builder, &table, &model).unwrap()));
-        if let Some(item) = save_changes_impl(cx, builder, &table, &model) {
+        let options = changeset_options(cx, meta_item).unwrap();
+        push(Annotatable::Item(changeset_impl(cx, builder, &options, &model).unwrap()));
+        if let Some(item) = save_changes_impl(cx, builder, &options, &model) {
             push(Annotatable::Item(item));
         }
     } else {
@@ -29,34 +30,65 @@ pub fn expand_changeset_for(
     }
 }
 
-fn changeset_tables(cx: &mut ExtCtxt, meta_item: &MetaItem) -> Option<InternedString> {
+struct ChangesetOptions {
+    table_name: ast::Ident,
+    skip_visibility: bool,
+}
+
+fn changeset_options(cx: &mut ExtCtxt, meta_item: &MetaItem) -> Result<ChangesetOptions, ()> {
     match meta_item.node {
         ast::MetaList(_, ref meta_items) => {
-            meta_items.iter().filter_map(|i| table_name(cx, i)).nth(0)
+            let table_name = try!(table_name(cx, &meta_items[0]));
+            let skip_visibility = try!(boolean_option(cx, &meta_items[1..], "__skip_visibility"))
+                .unwrap_or(false);
+            Ok(ChangesetOptions {
+                table_name: str_to_ident(&table_name),
+                skip_visibility: skip_visibility,
+            })
         }
         _ => usage_error(cx, meta_item),
     }
 }
 
-fn table_name(cx: &mut ExtCtxt, meta_item: &MetaItem) -> Option<InternedString> {
+fn table_name(cx: &mut ExtCtxt, meta_item: &MetaItem) -> Result<InternedString, ()> {
     match meta_item.node {
-        ast::MetaWord(ref word) => Some(word.clone()),
+        ast::MetaWord(ref word) => Ok(word.clone()),
         _ => usage_error(cx, meta_item),
     }
 }
 
-fn usage_error<T>(cx: &mut ExtCtxt, meta_item: &MetaItem) -> Option<T> {
+fn boolean_option(cx: &mut ExtCtxt, meta_items: &[P<MetaItem>], option_name: &str)
+    -> Result<Option<bool>, ()>
+{
+    if let Some(item) = meta_items.iter().find(|item| item.name() == option_name) {
+        match item.value_str() {
+            Some(ref s) if *s == "true" => Ok(Some(true)),
+            Some(ref s) if *s == "false" => Ok(Some(false)),
+            _ => {
+                cx.span_err(item.span,
+                    &format!("Expected {} to be in the form `option=\"true\"` or \
+                            option=\"false\"", option_name));
+                Err(())
+            }
+        }
+    } else {
+        Ok(None)
+    }
+}
+
+fn usage_error<T>(cx: &mut ExtCtxt, meta_item: &MetaItem) -> Result<T, ()> {
     cx.span_err(meta_item.span,
         "`changeset_for` must be used in the form `#[changeset_for(table1)]`");
-    None
+    Err(())
 }
 
 fn changeset_impl(
     cx: &mut ExtCtxt,
     builder: aster::AstBuilder,
-    table: &str,
+    options: &ChangesetOptions,
     model: &Model,
 ) -> Option<P<ast::Item>> {
+    let table: &str = &options.table_name.name.as_str();
     let ref struct_name = model.ty;
     let pk = model.primary_key_name();
     let attrs_for_changeset = model.attrs.iter().filter(|a| a.column_name != pk)
@@ -82,27 +114,33 @@ fn changeset_impl(
     )
 }
 
+#[allow(unused_mut)]
 fn save_changes_impl(
     cx: &mut ExtCtxt,
     builder: aster::AstBuilder,
-    table: &str,
+    options: &ChangesetOptions,
     model: &Model,
 ) -> Option<P<ast::Item>> {
     let ref struct_name = model.ty;
     let pk = model.primary_key_name();
     let sql_type = builder.path()
-        .segment(table).build()
+        .segment(&options.table_name).build()
         .segment("SqlType").build()
         .build();
     let table = builder.path()
-        .segment(table).build()
+        .segment(&options.table_name).build()
         .segment("table").build()
         .build();
+    let _pub = if options.skip_visibility {
+        quote_tokens!(cx, )
+    } else {
+        quote_tokens!(cx, pub)
+    };
     model.attrs.iter().find(|a| a.column_name == pk).and_then(|pk| {
         let pk_field = pk.field_name.unwrap();
         quote_item!(cx,
             impl<'a> $struct_name {
-                pub fn save_changes<T>(&self, connection: &::diesel::Connection)
+                $_pub fn save_changes<T>(&self, connection: &::diesel::Connection)
                     -> ::diesel::QueryResult<T> where
                     T: Queryable<$sql_type>,
                 {