Rollup merge of #99479 - Enselic:import-can-be-without-id, r=camelid

rustdoc-json: Remove doc FIXME for Import::id and explain

Also add some test and refactor related code a bit.

``@rustbot`` labels +A-rustdoc-json +T-rustdoc

Author: matthiaskrgr

src/librustdoc/json/conversions.rs

@@ -685,24 +685,18 @@ impl FromWithTcx<clean::Variant> for Variant {
 impl FromWithTcx<clean::Import> for Import {
     fn from_tcx(import: clean::Import, tcx: TyCtxt<'_>) -> Self {
         use clean::ImportKind::*;
-        match import.kind {
-            Simple(s) => Import {
-                source: import.source.path.whole_name(),
-                name: s.to_string(),
-                id: import.source.did.map(ItemId::from).map(|i| from_item_id(i, tcx)),
-                glob: false,
-            },
-            Glob => Import {
-                source: import.source.path.whole_name(),
-                name: import
-                    .source
-                    .path
-                    .last_opt()
-                    .unwrap_or_else(|| Symbol::intern("*"))
-                    .to_string(),
-                id: import.source.did.map(ItemId::from).map(|i| from_item_id(i, tcx)),
-                glob: true,
-            },
+        let (name, glob) = match import.kind {
+            Simple(s) => (s.to_string(), false),
+            Glob => (
+                import.source.path.last_opt().unwrap_or_else(|| Symbol::intern("*")).to_string(),
+                true,
+            ),
+        };
+        Import {
+            source: import.source.path.whole_name(),
+            name,
+            id: import.source.did.map(ItemId::from).map(|i| from_item_id(i, tcx)),
+            glob,
         }
     }
 }

src/rustdoc-json-types/lib.rs

@@ -591,8 +591,11 @@ pub struct Import {
     /// May be different from the last segment of `source` when renaming imports:
     /// `use source as name;`
     pub name: String,
-    /// The ID of the item being imported.
-    pub id: Option<Id>, // FIXME is this actually ever None?
+    /// The ID of the item being imported. Will be `None` in case of re-exports of primitives:
+    /// ```rust
+    /// pub use i32 as my_i32;
+    /// ```
+    pub id: Option<Id>,
     /// Whether this import uses a glob: `use source::*;`
     pub glob: bool,
 }

src/test/rustdoc-json/primitive.rs

@@ -12,3 +12,9 @@ mod usize {}
 // @has - "$.index[*][?(@.name=='checked_add')]"
 // @!is - "$.index[*][?(@.name=='checked_add')]" $local_crate_id
 // @!has - "$.index[*][?(@.name=='is_ascii_uppercase')]"
+
+// @is - "$.index[*][?(@.kind=='import' && @.inner.name=='my_i32')].inner.id" null
+pub use i32 as my_i32;
+
+// @is - "$.index[*][?(@.kind=='import' && @.inner.name=='u32')].inner.id" null
+pub use u32;