split processing module

Author: pvdrz

src/codegen/postprocessing.rs

@@ -0,0 +1,46 @@
+use syn::{Item, ItemForeignMod};
+
+pub(super) fn merge_extern_blocks(items: &mut Vec<Item>) {
+    // Keep all the extern blocks in a different `Vec` for faster search.
+    let mut foreign_mods = Vec::<ItemForeignMod>::new();
+
+    for item in std::mem::take(items) {
+        match item {
+            Item::ForeignMod(ItemForeignMod {
+                attrs,
+                abi,
+                brace_token,
+                items: foreign_items,
+            }) => {
+                let mut exists = false;
+                for foreign_mod in &mut foreign_mods {
+                    // Check if there is a extern block with the same ABI and
+                    // attributes.
+                    if foreign_mod.attrs == attrs && foreign_mod.abi == abi {
+                        // Merge the items of the two blocks.
+                        foreign_mod.items.extend_from_slice(&foreign_items);
+                        exists = true;
+                        break;
+                    }
+                }
+                // If no existing extern block had the same ABI and attributes, store
+                // it.
+                if !exists {
+                    foreign_mods.push(ItemForeignMod {
+                        attrs,
+                        abi,
+                        brace_token,
+                        items: foreign_items,
+                    });
+                }
+            }
+            // If the item is not an extern block, we don't have to do anything.
+            _ => items.push(item),
+        }
+    }
+
+    // Move all the extern blocks alongside the rest of the items.
+    for foreign_mod in foreign_mods {
+        items.push(Item::ForeignMod(foreign_mod));
+    }
+}

src/codegen/postprocessing/merge_extern_blocks.rs

@@ -0,0 +1,66 @@
+use proc_macro2::TokenStream;
+use quote::ToTokens;
+use syn::Item;
+
+use crate::BindgenOptions;
+
+mod merge_extern_blocks;
+mod sort_semantically;
+
+use merge_extern_blocks::merge_extern_blocks;
+use sort_semantically::sort_semantically;
+
+struct PostProcessingPass {
+    should_run: fn(&BindgenOptions) -> bool,
+    run: fn(&mut Vec<Item>),
+}
+
+// TODO: This can be a const fn when mutable references are allowed in const
+// context.
+macro_rules! pass {
+    ($pass:ident) => {
+        PostProcessingPass {
+            should_run: |options| options.$pass,
+            run: |items| $pass(items),
+        }
+    };
+}
+
+const PASSES: &[PostProcessingPass] =
+    &[pass!(merge_extern_blocks), pass!(sort_semantically)];
+
+pub(crate) fn postprocessing(
+    items: Vec<TokenStream>,
+    options: &BindgenOptions,
+) -> TokenStream {
+    let require_syn = PASSES.iter().any(|pass| (pass.should_run)(options));
+    if !require_syn {
+        return items.into_iter().collect();
+    }
+    let module_wrapped_tokens =
+        quote!(mod wrapper_for_sorting_hack { #( #items )* });
+
+    // This syn business is a hack, for now. This means that we are re-parsing already
+    // generated code using `syn` (as opposed to `quote`) because `syn` provides us more
+    // control over the elements.
+    // One caveat is that some of the items coming from `quote`d output might have
+    // multiple items within them. Hence, we have to wrap the incoming in a `mod`.
+    // The two `unwrap`s here are deliberate because
+    //      The first one won't panic because we build the `mod` and know it is there
+    //      The second one won't panic because we know original output has something in
+    //      it already.
+    let (_, mut items) = syn::parse2::<syn::ItemMod>(module_wrapped_tokens)
+        .unwrap()
+        .content
+        .unwrap();
+
+    for pass in PASSES {
+        if (pass.should_run)(options) {
+            (pass.run)(&mut items);
+        }
+    }
+
+    let synful_items = items.into_iter().map(|item| item.into_token_stream());
+
+    quote! { #( #synful_items )* }
+}

src/codegen/postprocessing/mod.rs

@@ -0,0 +1,24 @@
+use syn::Item;
+
+pub(super) fn sort_semantically(items: &mut [Item]) {
+    items.sort_by_key(|item| match item {
+        Item::Type(_) => 0,
+        Item::Struct(_) => 1,
+        Item::Const(_) => 2,
+        Item::Fn(_) => 3,
+        Item::Enum(_) => 4,
+        Item::Union(_) => 5,
+        Item::Static(_) => 6,
+        Item::Trait(_) => 7,
+        Item::TraitAlias(_) => 8,
+        Item::Impl(_) => 9,
+        Item::Mod(_) => 10,
+        Item::Use(_) => 11,
+        Item::Verbatim(_) => 12,
+        Item::ExternCrate(_) => 13,
+        Item::ForeignMod(_) => 14,
+        Item::Macro(_) => 15,
+        Item::Macro2(_) => 16,
+        _ => 18,
+    });
+}