1 files changed, 122 insertions, 0 deletions
diff --git a/src/librustdoc/json/ids.rs b/src/librustdoc/json/ids.rs
new file mode 100644
index 00000000000..737148bad4e
--- /dev/null
+++ b/src/librustdoc/json/ids.rs
@@ -0,0 +1,122 @@
+//! Id handling for rustdoc-json.
+//!
+//! Manages the creation of [`rustdoc_json_types::Id`] and the
+//! fact that these don't correspond exactly to [`DefId`], because
+//! [`rustdoc_json_types::Item`] doesn't correspond exactly to what
+//! other phases think of as an "item".
+
+use rustc_data_structures::fx::FxHashMap;
+use rustc_hir::def::DefKind;
+use rustc_hir::def_id::DefId;
+use rustc_span::{Symbol, sym};
+use rustdoc_json_types as types;
+
+use super::JsonRenderer;
+use crate::clean;
+
+pub(super) type IdInterner = FxHashMap<FullItemId, types::Id>;
+
+#[derive(Debug, Clone, Copy, Hash, PartialEq, Eq)]
+/// An uninterned id.
+///
+/// Each one corresponds to exactly one of both:
+/// 1. [`rustdoc_json_types::Item`].
+/// 2. [`rustdoc_json_types::Id`] transitively (as each `Item` has an `Id`).
+///
+/// It's *broadly* equivalent to a [`DefId`], but needs slightly more information
+/// to fully disambiguate items, because sometimes we choose to split a single HIR
+/// item into multiple JSON items, or have items with no corresponding HIR item.
+pub(super) struct FullItemId {
+    /// The "main" id of the item.
+    ///
+    /// In most cases this uniquely identifies the item, the other fields are just
+    /// used for edge-cases.
+    def_id: DefId,
+
+    /// An extra [`DefId`], which we need for:
+    ///
+    /// 1. Auto-trait impls synthesized by rustdoc.
+    /// 2. Blanket impls synthesized by rustdoc.
+    /// 3. Splitting of reexports of multiple items.
+    ///
+    ///    E.g:
+    ///
+    ///    ```rust
+    ///    mod module {
+    ///        pub struct Foo {} // Exists in type namespace
+    ///        pub fn Foo(){} // Exists in value namespace
+    ///    }
+    ///
+    ///    pub use module::Foo; // Imports both items
+    ///    ```
+    ///
+    ///    In HIR, the `pub use` is just 1 item, but in rustdoc-json it's 2, so
+    ///    we need to disambiguate.
+    extra_id: Option<DefId>,
+
+    /// Needed for `#[rustc_doc_primitive]` modules.
+    ///
+    /// For these, 1 [`DefId`] is used for both the primitive and the fake-module
+    /// that holds its docs.
+    ///
+    /// N.B. This only matters when documenting the standard library with
+    /// `--document-private-items`. Maybe we should delete that module, and
+    /// remove this.
+    name: Option<Symbol>,
+}
+
+impl JsonRenderer<'_> {
+    pub(crate) fn id_from_item_default(&self, item_id: clean::ItemId) -> types::Id {
+        self.id_from_item_inner(item_id, None, None)
+    }
+
+    fn id_from_item_inner(
+        &self,
+        item_id: clean::ItemId,
+        name: Option<Symbol>,
+        imported_id: Option<DefId>,
+    ) -> types::Id {
+        let (def_id, extra_id) = match item_id {
+            clean::ItemId::DefId(did) => (did, imported_id),
+            clean::ItemId::Blanket { for_, impl_id } => (for_, Some(impl_id)),
+            clean::ItemId::Auto { for_, trait_ } => (for_, Some(trait_)),
+        };
+
+        let name = match name {
+            Some(name) => Some(name),
+            None => {
+                // We need this workaround because primitive types' DefId actually refers to
+                // their parent module, which isn't present in the output JSON items. So
+                // instead, we directly get the primitive symbol
+                if matches!(self.tcx.def_kind(def_id), DefKind::Mod)
+                    && let Some(prim) = self
+                        .tcx
+                        .get_attrs(def_id, sym::rustc_doc_primitive)
+                        .find_map(|attr| attr.value_str())
+                {
+                    Some(prim)
+                } else {
+                    self.tcx.opt_item_name(def_id)
+                }
+            }
+        };
+
+        let key = FullItemId { def_id, extra_id, name };
+
+        let mut interner = self.id_interner.borrow_mut();
+        let len = interner.len();
+        *interner
+            .entry(key)
+            .or_insert_with(|| types::Id(len.try_into().expect("too many items in a crate")))
+    }
+
+    pub(crate) fn id_from_item(&self, item: &clean::Item) -> types::Id {
+        match item.kind {
+            clean::ItemKind::ImportItem(ref import) => {
+                let imported_id = import.source.did;
+                self.id_from_item_inner(item.item_id, item.name, imported_id)
+            }
+            _ => self.id_from_item_inner(item.item_id, item.name, None),
+        }
+    }
+}