From ec824a92d05caa1908cb25cbd5b969c8e995aaa7 Mon Sep 17 00:00:00 2001
From: Lukas Wirth <lukastw97@gmail.com>
Date: Wed, 17 Mar 2021 14:38:11 +0100
Subject: Better handling of block doc comments

---
 crates/hir_def/src/attr.rs | 83 +++++++++++++++++++++++++---------------------
 1 file changed, 45 insertions(+), 38 deletions(-)

(limited to 'crates/hir_def')

diff --git a/crates/hir_def/src/attr.rs b/crates/hir_def/src/attr.rs
index 7ba53ee5c..aeeb2c5cf 100644
--- a/crates/hir_def/src/attr.rs
+++ b/crates/hir_def/src/attr.rs
@@ -77,33 +77,19 @@ impl RawAttrs {
     pub(crate) const EMPTY: Self = Self { entries: None };
 
     pub(crate) fn new(owner: &dyn AttrsOwner, hygiene: &Hygiene) -> Self {
-        let attrs: Vec<_> = collect_attrs(owner).collect();
-        let entries = if attrs.is_empty() {
-            // Avoid heap allocation
-            None
-        } else {
-            Some(
-                attrs
-                    .into_iter()
-                    .enumerate()
-                    .flat_map(|(i, attr)| match attr {
-                        Either::Left(attr) => Attr::from_src(attr, hygiene).map(|attr| (i, attr)),
-                        Either::Right(comment) => comment.doc_comment().map(|doc| {
-                            (
-                                i,
-                                Attr {
-                                    index: 0,
-                                    input: Some(AttrInput::Literal(SmolStr::new(doc))),
-                                    path: ModPath::from(hir_expand::name!(doc)),
-                                },
-                            )
-                        }),
-                    })
-                    .map(|(i, attr)| Attr { index: i as u32, ..attr })
-                    .collect(),
-            )
-        };
-        Self { entries }
+        let entries = collect_attrs(owner)
+            .enumerate()
+            .flat_map(|(i, attr)| match attr {
+                Either::Left(attr) => Attr::from_src(attr, hygiene, i as u32),
+                Either::Right(comment) => comment.doc_comment().map(|doc| Attr {
+                    index: i as u32,
+                    input: Some(AttrInput::Literal(SmolStr::new(doc))),
+                    path: ModPath::from(hir_expand::name!(doc)),
+                }),
+            })
+            .collect::<Arc<_>>();
+
+        Self { entries: if entries.is_empty() { None } else { Some(entries) } }
     }
 
     fn from_attrs_owner(db: &dyn DefDatabase, owner: InFile<&dyn AttrsOwner>) -> Self {
@@ -162,7 +148,7 @@ impl RawAttrs {
                     let attr = ast::Attr::parse(&format!("#[{}]", tree)).ok()?;
                     // FIXME hygiene
                     let hygiene = Hygiene::new_unhygienic();
-                    Attr::from_src(attr, &hygiene).map(|attr| Attr { index, ..attr })
+                    Attr::from_src(attr, &hygiene, index)
                 });
 
                 let cfg_options = &crate_graph[krate].cfg_options;
@@ -325,15 +311,36 @@ impl Attrs {
             AttrInput::Literal(s) => Some(s),
             AttrInput::TokenTree(_) => None,
         });
-        // FIXME: Replace `Itertools::intersperse` with `Iterator::intersperse[_with]` until the
-        // libstd api gets stabilized (https://github.com/rust-lang/rust/issues/79524).
-        let docs = Itertools::intersperse(docs, &SmolStr::new_inline("\n"))
-            .map(|it| it.as_str())
-            .collect::<String>();
-        if docs.is_empty() {
+        let indent = docs
+            .clone()
+            .flat_map(|s| s.lines())
+            .filter(|line| !line.chars().all(|c| c.is_whitespace()))
+            .map(|line| line.chars().take_while(|c| c.is_whitespace()).count())
+            .min()
+            .unwrap_or(0);
+        let mut buf = String::new();
+        for doc in docs {
+            // str::lines doesn't yield anything for the empty string
+            if doc.is_empty() {
+                buf.push('\n');
+            } else {
+                buf.extend(Itertools::intersperse(
+                    doc.lines().map(|line| {
+                        line.char_indices()
+                            .nth(indent)
+                            .map_or(line, |(offset, _)| &line[offset..])
+                            .trim_end()
+                    }),
+                    "\n",
+                ));
+            }
+            buf.push('\n');
+        }
+        buf.pop();
+        if buf.is_empty() {
             None
         } else {
-            Some(Documentation(docs))
+            Some(Documentation(buf))
         }
     }
 }
@@ -407,7 +414,7 @@ pub enum AttrInput {
 }
 
 impl Attr {
-    fn from_src(ast: ast::Attr, hygiene: &Hygiene) -> Option<Attr> {
+    fn from_src(ast: ast::Attr, hygiene: &Hygiene, index: u32) -> Option<Attr> {
         let path = ModPath::from_src(ast.path()?, hygiene)?;
         let input = if let Some(lit) = ast.literal() {
             let value = match lit.kind() {
@@ -420,7 +427,7 @@ impl Attr {
         } else {
             None
         };
-        Some(Attr { index: 0, path, input })
+        Some(Attr { index, path, input })
     }
 
     /// Maps this lowered `Attr` back to its original syntax node.
@@ -508,7 +515,7 @@ impl<'a> AttrQuery<'a> {
         self.attrs().next().is_some()
     }
 
-    pub fn attrs(self) -> impl Iterator<Item = &'a Attr> {
+    pub fn attrs(self) -> impl Iterator<Item = &'a Attr> + Clone {
         let key = self.key;
         self.attrs
             .iter()
-- 
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