From 06fe27866920b3eaf6502f321ccb239cc617db10 Mon Sep 17 00:00:00 2001
From: Guillaume Gomez <guillaume1.gomez@gmail.com>
Date: Mon, 26 Oct 2020 15:01:39 +0100
Subject: [PATCH] Fix unindent behavior between different doc comments

---
 src/librustdoc/passes/unindent_comments.rs | 131 ++++++++++++---------
 1 file changed, 75 insertions(+), 56 deletions(-)

diff --git a/src/librustdoc/passes/unindent_comments.rs b/src/librustdoc/passes/unindent_comments.rs
index a9cf5a87f549..1c856b1da53f 100644
--- a/src/librustdoc/passes/unindent_comments.rs
+++ b/src/librustdoc/passes/unindent_comments.rs
@@ -1,7 +1,6 @@
 use std::cmp;
-use std::string::String;
 
-use crate::clean::{self, DocFragment, Item};
+use crate::clean::{self, DocFragment, DocFragmentKind, Item};
 use crate::core::DocContext;
 use crate::fold::{self, DocFolder};
 use crate::passes::Pass;
@@ -35,65 +34,85 @@ impl clean::Attributes {
 }
 
 fn unindent_fragments(docs: &mut Vec<DocFragment>) {
-    for fragment in docs {
-        fragment.doc = unindent(&fragment.doc);
-    }
-}
-
-fn unindent(s: &str) -> String {
-    let lines = s.lines().collect::<Vec<&str>>();
     let mut saw_first_line = false;
     let mut saw_second_line = false;
-    let min_indent = lines.iter().fold(usize::MAX, |min_indent, line| {
-        // After we see the first non-whitespace line, look at
-        // the line we have. If it is not whitespace, and therefore
-        // part of the first paragraph, then ignore the indentation
-        // level of the first line
-        let ignore_previous_indents =
-            saw_first_line && !saw_second_line && !line.chars().all(|c| c.is_whitespace());
-
-        let min_indent = if ignore_previous_indents { usize::MAX } else { min_indent };
-
-        if saw_first_line {
-            saw_second_line = true;
-        }
 
-        if line.chars().all(|c| c.is_whitespace()) {
-            min_indent
-        } else {
-            saw_first_line = true;
-            let mut whitespace = 0;
-            line.chars().all(|char| {
-                // Compare against either space or tab, ignoring whether they
-                // are mixed or not
-                if char == ' ' || char == '\t' {
-                    whitespace += 1;
-                    true
+    let add = if !docs.windows(2).all(|arr| arr[0].kind == arr[1].kind)
+        && docs.iter().any(|d| d.kind == DocFragmentKind::SugaredDoc)
+    {
+        // In case we have a mix of sugared doc comments and "raw" ones, we want the sugared one to
+        // "decide" how much the minimum indent will be.
+        1
+    } else {
+        0
+    };
+
+    let min_indent = match docs
+        .iter()
+        .map(|fragment| {
+            fragment.doc.lines().fold(usize::MAX, |min_indent, line| {
+                // After we see the first non-whitespace line, look at
+                // the line we have. If it is not whitespace, and therefore
+                // part of the first paragraph, then ignore the indentation
+                // level of the first line
+                let ignore_previous_indents =
+                    saw_first_line && !saw_second_line && !line.chars().all(|c| c.is_whitespace());
+
+                let min_indent = if ignore_previous_indents { usize::MAX } else { min_indent };
+
+                if saw_first_line {
+                    saw_second_line = true;
+                }
+
+                if line.chars().all(|c| c.is_whitespace()) {
+                    min_indent
                 } else {
-                    false
+                    saw_first_line = true;
+                    // Compare against either space or tab, ignoring whether they are
+                    // mixed or not.
+                    let whitespace = line.chars().take_while(|c| *c == ' ' || *c == '\t').count();
+                    cmp::min(min_indent, whitespace)
+                        + if fragment.kind == DocFragmentKind::SugaredDoc { 0 } else { add }
                 }
-            });
-            cmp::min(min_indent, whitespace)
+            })
+        })
+        .min()
+    {
+        Some(x) => x,
+        None => return,
+    };
+
+    let mut first_ignored = false;
+    for fragment in docs {
+        let lines: Vec<_> = fragment.doc.lines().collect();
+
+        if !lines.is_empty() {
+            let min_indent = if fragment.kind != DocFragmentKind::SugaredDoc && min_indent > 0 {
+                min_indent - add
+            } else {
+                min_indent
+            };
+
+            let mut iter = lines.iter();
+            let mut result = if !first_ignored {
+                first_ignored = true;
+                vec![iter.next().unwrap().trim_start().to_string()]
+            } else {
+                Vec::new()
+            };
+            result.extend_from_slice(
+                &iter
+                    .map(|&line| {
+                        if line.chars().all(|c| c.is_whitespace()) {
+                            line.to_string()
+                        } else {
+                            assert!(line.len() >= min_indent);
+                            line[min_indent..].to_string()
+                        }
+                    })
+                    .collect::<Vec<_>>(),
+            );
+            fragment.doc = result.join("\n");
         }
-    });
-
-    if !lines.is_empty() {
-        let mut unindented = vec![lines[0].trim_start().to_string()];
-        unindented.extend_from_slice(
-            &lines[1..]
-                .iter()
-                .map(|&line| {
-                    if line.chars().all(|c| c.is_whitespace()) {
-                        line.to_string()
-                    } else {
-                        assert!(line.len() >= min_indent);
-                        line[min_indent..].to_string()
-                    }
-                })
-                .collect::<Vec<_>>(),
-        );
-        unindented.join("\n")
-    } else {
-        s.to_string()
     }
 }