rustdoc: Use own logic to print #[repr(..)] attributes in JSON output.

Author: obi1kenobi

src/librustdoc/clean/types.rs

@@ -772,7 +772,15 @@ impl Item {
             .other_attrs
             .iter()
             .filter_map(|attr| {
-                if keep_as_is {
+                // We have separate pretty-printing logic for `#[repr(..)]` attributes.
+                // For example, there are circumstances where `#[repr(transparent)]` is applied
+                // but should not be publicly shown in rustdoc because it isn't public API.
+                if keep_as_is
+                    && !matches!(
+                        attr,
+                        rustc_hir::Attribute::Parsed(rustc_attr_parsing::AttributeKind::Repr(..))
+                    )
+                {
                     Some(rustc_hir_pretty::attribute_to_string(&tcx, attr))
                 } else if ALLOWED_ATTRIBUTES.contains(&attr.name_or_empty()) {
                     Some(
@@ -786,8 +794,7 @@ impl Item {
                 }
             })
             .collect();
-        if !keep_as_is
-            && let Some(def_id) = self.def_id()
+        if let Some(def_id) = self.def_id()
             && let ItemType::Struct | ItemType::Enum | ItemType::Union = self.type_()
         {
             let adt = tcx.adt_def(def_id);

src/rustdoc-json-types/lib.rs

@@ -30,7 +30,7 @@ pub type FxHashMap<K, V> = HashMap<K, V>; // re-export for use in src/librustdoc
 /// This integer is incremented with every breaking change to the API,
 /// and is returned along with the JSON blob as [`Crate::format_version`].
 /// Consuming code should assert that this value matches the format version(s) that it supports.
-pub const FORMAT_VERSION: u32 = 40;
+pub const FORMAT_VERSION: u32 = 41;
 
 /// The root of the emitted JSON blob.
 ///

tests/rustdoc-json/attrs/repr_align.rs

@@ -0,0 +1,8 @@
+#![no_std]
+
+//@ is "$.index[*][?(@.name=='Aligned')].attrs" '["#[repr(align(4))]"]'
+#[repr(align(4))]
+pub struct Aligned {
+    a: i8,
+    b: i64,
+}

tests/rustdoc-json/attrs/repr_c.rs

@@ -0,0 +1,18 @@
+#![no_std]
+
+//@ is "$.index[*][?(@.name=='ReprCStruct')].attrs" '["#[repr(C)]"]'
+#[repr(C)]
+pub struct ReprCStruct(pub i64);
+
+//@ is "$.index[*][?(@.name=='ReprCEnum')].attrs" '["#[repr(C)]"]'
+#[repr(C)]
+pub enum ReprCEnum {
+    First,
+}
+
+//@ is "$.index[*][?(@.name=='ReprCUnion')].attrs" '["#[repr(C)]"]'
+#[repr(C)]
+pub union ReprCUnion {
+    pub left: i64,
+    pub right: u64,
+}

tests/rustdoc-json/attrs/repr_combination.rs

@@ -0,0 +1,79 @@
+#![no_std]
+
+// Combinations of `#[repr(..)]` attributes.
+// Rustdoc JSON emits normalized output, regardless of the original source.
+
+//@ is "$.index[*][?(@.name=='ReprCI8')].attrs" '["#[repr(C, i8)]"]'
+#[repr(C, i8)]
+pub enum ReprCI8 {
+    First,
+}
+
+//@ is "$.index[*][?(@.name=='SeparateReprCI16')].attrs" '["#[repr(C, i16)]"]'
+#[repr(C)]
+#[repr(i16)]
+pub enum SeparateReprCI16 {
+    First,
+}
+
+//@ is "$.index[*][?(@.name=='ReversedReprCUsize')].attrs" '["#[repr(C, usize)]"]'
+#[repr(usize, C)]
+pub enum ReversedReprCUsize {
+    First,
+}
+
+//@ is "$.index[*][?(@.name=='ReprCPacked')].attrs" '["#[repr(C, packed(1))]"]'
+#[repr(C, packed)]
+pub struct ReprCPacked {
+    a: i8,
+    b: i64,
+}
+
+//@ is "$.index[*][?(@.name=='SeparateReprCPacked')].attrs" '["#[repr(C, packed(2))]"]'
+#[repr(C)]
+#[repr(packed(2))]
+pub struct SeparateReprCPacked {
+    a: i8,
+    b: i64,
+}
+
+//@ is "$.index[*][?(@.name=='ReversedReprCPacked')].attrs" '["#[repr(C, packed(2))]"]'
+#[repr(packed(2), C)]
+pub struct ReversedReprCPacked {
+    a: i8,
+    b: i64,
+}
+
+//@ is "$.index[*][?(@.name=='ReprCAlign')].attrs" '["#[repr(C, align(16))]"]'
+#[repr(C, align(16))]
+pub struct ReprCAlign {
+    a: i8,
+    b: i64,
+}
+
+//@ is "$.index[*][?(@.name=='SeparateReprCAlign')].attrs" '["#[repr(C, align(2))]"]'
+#[repr(C)]
+#[repr(align(2))]
+pub struct SeparateReprCAlign {
+    a: i8,
+    b: i64,
+}
+
+//@ is "$.index[*][?(@.name=='ReversedReprCAlign')].attrs" '["#[repr(C, align(2))]"]'
+#[repr(align(2), C)]
+pub struct ReversedReprCAlign {
+    a: i8,
+    b: i64,
+}
+
+//@ is "$.index[*][?(@.name=='AlignedExplicitRepr')].attrs" '["#[repr(C, align(16), isize)]"]'
+#[repr(C, align(16), isize)]
+pub enum AlignedExplicitRepr {
+    First,
+}
+
+//@ is "$.index[*][?(@.name=='ReorderedAlignedExplicitRepr')].attrs" '["#[repr(C, align(16), isize)]"]'
+#[repr(isize, C, align(16))]
+pub enum ReorderedAlignedExplicitRepr {
+    First,
+}

tests/rustdoc-json/attrs/repr_int_enum.rs

@@ -0,0 +1,19 @@
+#![no_std]
+
+//@ is "$.index[*][?(@.name=='I8')].attrs" '["#[repr(i8)]"]'
+#[repr(i8)]
+pub enum I8 {
+    First,
+}
+
+//@ is "$.index[*][?(@.name=='I32')].attrs" '["#[repr(i32)]"]'
+#[repr(i32)]
+pub enum I32 {
+    First,
+}
+
+//@ is "$.index[*][?(@.name=='Usize')].attrs" '["#[repr(usize)]"]'
+#[repr(usize)]
+pub enum Usize {
+    First,
+}

tests/rustdoc-json/attrs/repr_packed.rs

@@ -0,0 +1,18 @@
+#![no_std]
+
+// Note the normalization:
+// `#[repr(packed)]` in source becomes `#[repr(packed(1))]` in rustdoc JSON.
+//
+//@ is "$.index[*][?(@.name=='Packed')].attrs" '["#[repr(packed(1))]"]'
+#[repr(packed)]
+pub struct Packed {
+    a: i8,
+    b: i64,
+}
+
+//@ is "$.index[*][?(@.name=='PackedAligned')].attrs" '["#[repr(packed(4))]"]'
+#[repr(packed(4))]
+pub struct PackedAligned {
+    a: i8,
+    b: i64,
+}

tests/rustdoc-json/attrs/repr_transparent.rs

@@ -0,0 +1,35 @@
+#![no_std]
+
+// Rustdoc JSON *only* includes `#[repr(transparent)]`
+// if the transparency is public API:
+// - if a non-1-ZST field exists, it has to be public
+// - otherwise, all fields are 1-ZST and at least one of them is public
+
+// Here, the non-1-ZST field is public.
+// We expect `#[repr(transparent)]` in the attributes.
+//
+//@ is "$.index[*][?(@.name=='Transparent')].attrs" '["#[repr(transparent)]"]'
+#[repr(transparent)]
+pub struct Transparent(pub i64);
+
+// Here the non-1-ZST field isn't public, so the attribute isn't included.
+//
+//@ has "$.index[*][?(@.name=='TransparentNonPub')]"
+//@ is "$.index[*][?(@.name=='TransparentNonPub')].attrs" '[]'
+#[repr(transparent)]
+pub struct TransparentNonPub(i64);
+
+// Only 1-ZST fields here, and one of them is public.
+// We expect `#[repr(transparent)]` in the attributes.
+//
+//@ is "$.index[*][?(@.name=='AllZst')].attrs" '["#[repr(transparent)]"]'
+#[repr(transparent)]
+pub struct AllZst<'a>(pub core::marker::PhantomData<&'a ()>, ());
+
+// Only 1-ZST fields here but none of them are public.
+// The attribute isn't included.
+//
+//@ has "$.index[*][?(@.name=='AllZstNotPublic')]"
+//@ is "$.index[*][?(@.name=='AllZstNotPublic')].attrs" '[]'
+#[repr(transparent)]
+pub struct AllZstNotPublic<'a>(core::marker::PhantomData<&'a ()>, ());