Auto merge of #12433 - J-ZhengLi:issue12197, r=dswij

fix [`missing_docs_in_private_items`] on some proc macros

fixes: #12197

---

changelog: [`missing_docs_in_private_items`] support manually search for docs as fallback method

clippy_lints/src/missing_doc.rs

@@ -8,6 +8,7 @@
 use clippy_utils::attrs::is_doc_hidden;
 use clippy_utils::diagnostics::span_lint;
 use clippy_utils::is_from_proc_macro;
+use clippy_utils::source::snippet_opt;
 use rustc_ast::ast::{self, MetaItem, MetaItemKind};
 use rustc_hir as hir;
 use rustc_hir::def_id::LocalDefId;
@@ -32,6 +33,13 @@
     "detects missing documentation for private members"
 }
 
+macro_rules! note_prev_span_then_ret {
+    ($prev_span:expr, $span:expr) => {{
+        $prev_span = Some($span);
+        return;
+    }};
+}
+
 pub struct MissingDoc {
     /// Whether to **only** check for missing documentation in items visible within the current
     /// crate. For example, `pub(crate)` items.
@@ -39,6 +47,8 @@ pub struct MissingDoc {
     /// Stack of whether #[doc(hidden)] is set
     /// at each level which has lint attributes.
     doc_hidden_stack: Vec<bool>,
+    /// Used to keep tracking of the previous item, field or variants etc, to get the search span.
+    prev_span: Option<Span>,
 }
 
 impl Default for MissingDoc {
@@ -54,6 +64,7 @@ pub fn new(crate_items_only: bool) -> Self {
         Self {
             crate_items_only,
             doc_hidden_stack: vec![false],
+            prev_span: None,
         }
     }
 
@@ -108,7 +119,8 @@ fn check_missing_docs_attrs(
 
         let has_doc = attrs
             .iter()
-            .any(|a| a.doc_str().is_some() || Self::has_include(a.meta()));
+            .any(|a| a.doc_str().is_some() || Self::has_include(a.meta()))
+            || matches!(self.search_span(sp), Some(span) if span_to_snippet_contains_docs(cx, span));
 
         if !has_doc {
             span_lint(
@@ -119,6 +131,32 @@ fn check_missing_docs_attrs(
             );
         }
     }
+
+    /// Return a span to search for doc comments manually.
+    ///
+    /// # Example
+    /// ```ignore
+    /// fn foo() { ... }
+    /// ^^^^^^^^^^^^^^^^ prev_span
+    ///                ↑
+    /// |  search_span |
+    /// ↓
+    /// fn bar() { ... }
+    /// ^^^^^^^^^^^^^^^^ cur_span
+    /// ```
+    fn search_span(&self, cur_span: Span) -> Option<Span> {
+        let prev_span = self.prev_span?;
+        let start_pos = if prev_span.contains(cur_span) {
+            // In case when the prev_span is an entire struct, or enum,
+            // and the current span is a field, or variant, we need to search from
+            // the starting pos of the previous span.
+            prev_span.lo()
+        } else {
+            prev_span.hi()
+        };
+        let search_span = cur_span.with_lo(start_pos).with_hi(cur_span.lo());
+        Some(search_span)
+    }
 }
 
 impl_lint_pass!(MissingDoc => [MISSING_DOCS_IN_PRIVATE_ITEMS]);
@@ -138,6 +176,10 @@ fn check_crate(&mut self, cx: &LateContext<'tcx>) {
         self.check_missing_docs_attrs(cx, CRATE_DEF_ID, attrs, cx.tcx.def_span(CRATE_DEF_ID), "the", "crate");
     }
 
+    fn check_crate_post(&mut self, _: &LateContext<'tcx>) {
+        self.prev_span = None;
+    }
+
     fn check_item(&mut self, cx: &LateContext<'tcx>, it: &'tcx hir::Item<'_>) {
         match it.kind {
             hir::ItemKind::Fn(..) => {
@@ -145,7 +187,7 @@ fn check_item(&mut self, cx: &LateContext<'tcx>, it: &'tcx hir::Item<'_>) {
                 if it.ident.name == sym::main {
                     let at_root = cx.tcx.local_parent(it.owner_id.def_id) == CRATE_DEF_ID;
                     if at_root {
-                        return;
+                        note_prev_span_then_ret!(self.prev_span, it.span);
                     }
                 }
             },
@@ -164,7 +206,7 @@ fn check_item(&mut self, cx: &LateContext<'tcx>, it: &'tcx hir::Item<'_>) {
             | hir::ItemKind::ForeignMod { .. }
             | hir::ItemKind::GlobalAsm(..)
             | hir::ItemKind::Impl { .. }
-            | hir::ItemKind::Use(..) => return,
+            | hir::ItemKind::Use(..) => note_prev_span_then_ret!(self.prev_span, it.span),
         };
 
         let (article, desc) = cx.tcx.article_and_description(it.owner_id.to_def_id());
@@ -173,6 +215,7 @@ fn check_item(&mut self, cx: &LateContext<'tcx>, it: &'tcx hir::Item<'_>) {
         if !is_from_proc_macro(cx, it) {
             self.check_missing_docs_attrs(cx, it.owner_id.def_id, attrs, it.span, article, desc);
         }
+        self.prev_span = Some(it.span);
     }
 
     fn check_trait_item(&mut self, cx: &LateContext<'tcx>, trait_item: &'tcx hir::TraitItem<'_>) {
@@ -182,16 +225,17 @@ fn check_trait_item(&mut self, cx: &LateContext<'tcx>, trait_item: &'tcx hir::Tr
         if !is_from_proc_macro(cx, trait_item) {
             self.check_missing_docs_attrs(cx, trait_item.owner_id.def_id, attrs, trait_item.span, article, desc);
         }
+        self.prev_span = Some(trait_item.span);
     }
 
     fn check_impl_item(&mut self, cx: &LateContext<'tcx>, impl_item: &'tcx hir::ImplItem<'_>) {
         // If the method is an impl for a trait, don't doc.
         if let Some(cid) = cx.tcx.associated_item(impl_item.owner_id).impl_container(cx.tcx) {
             if cx.tcx.impl_trait_ref(cid).is_some() {
-                return;
+                note_prev_span_then_ret!(self.prev_span, impl_item.span);
             }
         } else {
-            return;
+            note_prev_span_then_ret!(self.prev_span, impl_item.span);
         }
 
         let (article, desc) = cx.tcx.article_and_description(impl_item.owner_id.to_def_id());
@@ -199,6 +243,7 @@ fn check_impl_item(&mut self, cx: &LateContext<'tcx>, impl_item: &'tcx hir::Impl
         if !is_from_proc_macro(cx, impl_item) {
             self.check_missing_docs_attrs(cx, impl_item.owner_id.def_id, attrs, impl_item.span, article, desc);
         }
+        self.prev_span = Some(impl_item.span);
     }
 
     fn check_field_def(&mut self, cx: &LateContext<'tcx>, sf: &'tcx hir::FieldDef<'_>) {
@@ -208,6 +253,7 @@ fn check_field_def(&mut self, cx: &LateContext<'tcx>, sf: &'tcx hir::FieldDef<'_
                 self.check_missing_docs_attrs(cx, sf.def_id, attrs, sf.span, "a", "struct field");
             }
         }
+        self.prev_span = Some(sf.span);
     }
 
     fn check_variant(&mut self, cx: &LateContext<'tcx>, v: &'tcx hir::Variant<'_>) {
@@ -215,5 +261,13 @@ fn check_variant(&mut self, cx: &LateContext<'tcx>, v: &'tcx hir::Variant<'_>) {
         if !is_from_proc_macro(cx, v) {
             self.check_missing_docs_attrs(cx, v.def_id, attrs, v.span, "a", "variant");
         }
+        self.prev_span = Some(v.span);
     }
 }
+
+fn span_to_snippet_contains_docs(cx: &LateContext<'_>, search_span: Span) -> bool {
+    let Some(snippet) = snippet_opt(cx, search_span) else {
+        return false;
+    };
+    snippet.lines().rev().any(|line| line.trim().starts_with("///"))
+}

tests/ui/auxiliary/proc_macro_attr.rs

@@ -11,8 +11,8 @@
 use syn::spanned::Spanned;
 use syn::token::Star;
 use syn::{
-    parse_macro_input, parse_quote, FnArg, ImplItem, ItemFn, ItemImpl, ItemTrait, Lifetime, Pat, PatIdent, PatType,
+    parse_macro_input, parse_quote, FnArg, ImplItem, ItemFn, ItemImpl, ItemStruct, ItemTrait, Lifetime, Pat, PatIdent,
-    Signature, TraitItem, Type,
+    PatType, Signature, TraitItem, Type, Visibility,
 };
 
 #[proc_macro_attribute]
@@ -101,9 +101,7 @@ pub fn fake_main(_attr: TokenStream, item: TokenStream) -> TokenStream {
     let mut item = parse_macro_input!(item as ItemFn);
     let span = item.block.brace_token.span;
 
-    if item.sig.asyncness.is_some() {
+    item.sig.asyncness = None;
-        item.sig.asyncness = None;
-    }
 
     let crate_name = quote! { fake_crate };
     let block = item.block;
@@ -128,7 +126,7 @@ pub fn block_on<F: ::std::future::Future>(_fut: F) {}
 
 #[proc_macro_attribute]
 pub fn fake_desugar_await(_args: TokenStream, input: TokenStream) -> TokenStream {
-    let mut async_fn = syn::parse_macro_input!(input as syn::ItemFn);
+    let mut async_fn = parse_macro_input!(input as syn::ItemFn);
 
     for stmt in &mut async_fn.block.stmts {
         if let syn::Stmt::Expr(syn::Expr::Match(syn::ExprMatch { expr: scrutinee, .. }), _) = stmt {
@@ -145,3 +143,23 @@ pub fn fake_desugar_await(_args: TokenStream, input: TokenStream) -> TokenStream
 
     quote!(#async_fn).into()
 }
+
+#[proc_macro_attribute]
+pub fn rewrite_struct(_args: TokenStream, input: TokenStream) -> TokenStream {
+    let mut item_struct = parse_macro_input!(input as syn::ItemStruct);
+    // remove struct attributes including doc comments.
+    item_struct.attrs = vec![];
+    if let Visibility::Public(token) = item_struct.vis {
+        // set vis to `pub(crate)` to trigger `missing_docs_in_private_items` lint.
+        let new_vis: Visibility = syn::parse_quote_spanned!(token.span() => pub(crate));
+        item_struct.vis = new_vis;
+    }
+    if let syn::Fields::Named(fields) = &mut item_struct.fields {
+        for field in &mut fields.named {
+            // remove all attributes from fields as well.
+            field.attrs = vec![];
+        }
+    }
+
+    quote!(#item_struct).into()
+}

tests/ui/missing_doc.rs

@@ -1,5 +1,6 @@
 //@needs-asm-support
 //@aux-build: proc_macros.rs
+//@aux-build: proc_macro_attr.rs
 
 #![warn(clippy::missing_docs_in_private_items)]
 // When denying at the crate level, be sure to not get random warnings from the
@@ -8,6 +9,8 @@
 //! Some garbage docs for the crate here
 #![doc = "More garbage"]
 
+#[macro_use]
+extern crate proc_macro_attr;
 extern crate proc_macros;
 
 use proc_macros::with_span;
@@ -112,3 +115,12 @@ fn main() {}
 with_span!(span pub fn foo_pm() {});
 with_span!(span pub static FOO_PM: u32 = 0;);
 with_span!(span pub const FOO2_PM: u32 = 0;);
+
+// issue #12197
+// Undocumented field originated inside of spanned proc-macro attribute
+/// Some dox for struct.
+#[rewrite_struct]
+pub struct Test {
+    /// Dox
+    a: u8,
+}

tests/ui/missing_doc.stderr

@@ -1,5 +1,5 @@
 error: missing documentation for a type alias
-  --> tests/ui/missing_doc.rs:16:1
+  --> tests/ui/missing_doc.rs:19:1
    |
 LL | type Typedef = String;
    | ^^^^^^^^^^^^^^^^^^^^^^
@@ -8,19 +8,19 @@ LL | type Typedef = String;
    = help: to override `-D warnings` add `#[allow(clippy::missing_docs_in_private_items)]`
 
 error: missing documentation for a module
-  --> tests/ui/missing_doc.rs:19:1
+  --> tests/ui/missing_doc.rs:22:1
    |
 LL | mod module_no_dox {}
    | ^^^^^^^^^^^^^^^^^^^^
 
 error: missing documentation for a function
-  --> tests/ui/missing_doc.rs:25:1
+  --> tests/ui/missing_doc.rs:28:1
    |
 LL | fn foo3() {}
    | ^^^^^^^^^^^^
 
 error: missing documentation for an enum
-  --> tests/ui/missing_doc.rs:39:1
+  --> tests/ui/missing_doc.rs:42:1
    |
 LL | / enum Baz {
 LL | |     BazA { a: isize, b: isize },
@@ -29,43 +29,43 @@ LL | | }
    | |_^
 
 error: missing documentation for a variant
-  --> tests/ui/missing_doc.rs:40:5
+  --> tests/ui/missing_doc.rs:43:5
    |
 LL |     BazA { a: isize, b: isize },
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: missing documentation for a struct field
-  --> tests/ui/missing_doc.rs:40:12
+  --> tests/ui/missing_doc.rs:43:12
    |
 LL |     BazA { a: isize, b: isize },
    |            ^^^^^^^^
 
 error: missing documentation for a struct field
-  --> tests/ui/missing_doc.rs:40:22
+  --> tests/ui/missing_doc.rs:43:22
    |
 LL |     BazA { a: isize, b: isize },
    |                      ^^^^^^^^
 
 error: missing documentation for a variant
-  --> tests/ui/missing_doc.rs:41:5
+  --> tests/ui/missing_doc.rs:44:5
    |
 LL |     BarB,
    |     ^^^^
 
 error: missing documentation for a constant
-  --> tests/ui/missing_doc.rs:65:1
+  --> tests/ui/missing_doc.rs:68:1
    |
 LL | const FOO: u32 = 0;
    | ^^^^^^^^^^^^^^^^^^^
 
 error: missing documentation for a static
-  --> tests/ui/missing_doc.rs:74:1
+  --> tests/ui/missing_doc.rs:77:1
    |
 LL | static BAR: u32 = 0;
    | ^^^^^^^^^^^^^^^^^^^^
 
 error: missing documentation for a module
-  --> tests/ui/missing_doc.rs:83:1
+  --> tests/ui/missing_doc.rs:86:1
    |
 LL | / mod internal_impl {
 LL | |     /// dox
@@ -77,13 +77,13 @@ LL | | }
    | |_^
 
 error: missing documentation for a function
-  --> tests/ui/missing_doc.rs:88:5
+  --> tests/ui/missing_doc.rs:91:5
    |
 LL |     fn undocumented3() {}
    |     ^^^^^^^^^^^^^^^^^^^^^
 
 error: missing documentation for a function
-  --> tests/ui/missing_doc.rs:94:9
+  --> tests/ui/missing_doc.rs:97:9
    |
 LL |         fn also_undocumented2() {}
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^