Auto merge of #136784 - yotamofek:pr/rustdoc-remove-buffer-take2, r=<try>

Nuke `Buffer` abstraction from `librustdoc`, take 2 💣

In #136656 I found out that the for_html field in the Buffer struct was never read, and pondered if Buffer had any utility at all. `@GuillaumeGomez` said he agrees that it can be just removed. So this PR is me removing it. So, r? `@aDotInTheVoid` , maybe?

Supersedes #136748

Author: bors

src/librustdoc/html/format.rs

@@ -37,114 +37,36 @@ use crate::html::render::Context;
 use crate::joined::Joined as _;
 use crate::passes::collect_intra_doc_links::UrlFragment;
 
-pub(crate) trait Print {
-    fn print(self, buffer: &mut Buffer);
-}
-
-impl<F> Print for F
-where
-    F: FnOnce(&mut Buffer),
-{
-    fn print(self, buffer: &mut Buffer) {
-        (self)(buffer)
-    }
-}
-
-impl Print for String {
-    fn print(self, buffer: &mut Buffer) {
-        buffer.write_str(&self);
-    }
-}
-
-impl Print for &'_ str {
-    fn print(self, buffer: &mut Buffer) {
-        buffer.write_str(self);
-    }
-}
+/// This macro is the same as [`std::write!`] for [`String`]s, but swallows the returned `Result`,
+/// since writing into a `String` can never fail.
+macro_rules! write_str {
+    ($dst:expr, $($arg:tt)*) => {{
+        // make sure $dst is a `String` (or `&mut String`)
+        trait AssertString {
+            fn assert_string(&mut self) {}
+        }
+        impl AssertString for ::std::string::String {}
+        $dst.assert_string();
 
-#[derive(Debug, Clone)]
-pub(crate) struct Buffer {
-    for_html: bool,
-    buffer: String,
+        let _ = $dst.write_fmt(::std::format_args!($($arg)*));
+    }};
 }
+/// This macro is the same as [`std::writeln!`] for [`String`]s, but swallows the returned `Result`,
+/// since writing into a `String` can never fail.
+macro_rules! writeln_str {
+    ($dst:expr, $($arg:tt)*) => {{
+        // make sure $dst is a `String` (or `&mut String`)
+        trait AssertString {
+            fn assert_string(&mut self) {}
+        }
+        impl AssertString for ::std::string::String {}
+        $dst.assert_string();
 
-impl core::fmt::Write for Buffer {
-    #[inline]
-    fn write_str(&mut self, s: &str) -> fmt::Result {
-        self.buffer.write_str(s)
-    }
-
-    #[inline]
-    fn write_char(&mut self, c: char) -> fmt::Result {
-        self.buffer.write_char(c)
-    }
-
-    #[inline]
-    fn write_fmt(&mut self, args: fmt::Arguments<'_>) -> fmt::Result {
-        self.buffer.write_fmt(args)
-    }
+        let _ = $dst.write_fmt(::std::format_args_nl!($($arg)*));
+    }};
 }
 
-impl Buffer {
-    pub(crate) fn empty_from(v: &Buffer) -> Buffer {
-        Buffer { for_html: v.for_html, buffer: String::new() }
-    }
-
-    pub(crate) fn html() -> Buffer {
-        Buffer { for_html: true, buffer: String::new() }
-    }
-
-    pub(crate) fn new() -> Buffer {
-        Buffer { for_html: false, buffer: String::new() }
-    }
-
-    pub(crate) fn is_empty(&self) -> bool {
-        self.buffer.is_empty()
-    }
-
-    pub(crate) fn into_inner(self) -> String {
-        self.buffer
-    }
-
-    pub(crate) fn push(&mut self, c: char) {
-        self.buffer.push(c);
-    }
-
-    pub(crate) fn push_str(&mut self, s: &str) {
-        self.buffer.push_str(s);
-    }
-
-    pub(crate) fn push_buffer(&mut self, other: Buffer) {
-        self.buffer.push_str(&other.buffer);
-    }
-
-    // Intended for consumption by write! and writeln! (std::fmt) but without
-    // the fmt::Result return type imposed by fmt::Write (and avoiding the trait
-    // import).
-    pub(crate) fn write_str(&mut self, s: &str) {
-        self.buffer.push_str(s);
-    }
-
-    // Intended for consumption by write! and writeln! (std::fmt) but without
-    // the fmt::Result return type imposed by fmt::Write (and avoiding the trait
-    // import).
-    pub(crate) fn write_fmt(&mut self, v: fmt::Arguments<'_>) {
-        self.buffer.write_fmt(v).unwrap();
-    }
-
-    pub(crate) fn to_display<T: Print>(mut self, t: T) -> String {
-        t.print(&mut self);
-        self.into_inner()
-    }
-
-    pub(crate) fn reserve(&mut self, additional: usize) {
-        self.buffer.reserve(additional)
-    }
-
-    pub(crate) fn len(&self) -> usize {
-        self.buffer.len()
-    }
-}
+pub(crate) use {write_str, writeln_str};
 
 pub(crate) fn print_generic_bounds<'a, 'tcx: 'a>(
     bounds: &'a [clean::GenericBound],
@@ -767,12 +689,14 @@ pub(crate) fn href_relative_parts<'fqp>(
 }
 
 pub(crate) fn link_tooltip(did: DefId, fragment: &Option<UrlFragment>, cx: &Context<'_>) -> String {
+    use write_str as write;
+
     let cache = cx.cache();
     let Some((fqp, shortty)) = cache.paths.get(&did).or_else(|| cache.external_paths.get(&did))
     else {
         return String::new();
     };
-    let mut buf = Buffer::new();
+    let mut buf = String::new();
     let fqp = if *shortty == ItemType::Primitive {
         // primitives are documented in a crate, but not actually part of it
         &fqp[fqp.len() - 1..]
@@ -792,7 +716,7 @@ pub(crate) fn link_tooltip(did: DefId, fragment: &Option<UrlFragment>, cx: &Cont
             write!(buf, "::{component}");
         }
     }
-    buf.into_inner()
+    buf
 }
 
 /// Used to render a [`clean::Path`].

src/librustdoc/html/highlight.rs

@@ -14,7 +14,7 @@ use rustc_span::edition::Edition;
 use rustc_span::symbol::Symbol;
 use rustc_span::{BytePos, DUMMY_SP, Span};
 
-use super::format::{self, Buffer};
+use super::format;
 use crate::clean::PrimitiveType;
 use crate::html::escape::EscapeBodyText;
 use crate::html::render::{Context, LinkFromSrc};
@@ -48,7 +48,7 @@ pub(crate) enum Tooltip {
 /// Highlights `src` as an inline example, returning the HTML output.
 pub(crate) fn render_example_with_highlighting(
     src: &str,
-    out: &mut Buffer,
+    out: &mut String,
     tooltip: Tooltip,
     playground_button: Option<&str>,
     extra_classes: &[String],
@@ -59,12 +59,14 @@ pub(crate) fn render_example_with_highlighting(
 }
 
 fn write_header(
-    out: &mut Buffer,
+    out: &mut String,
     class: &str,
-    extra_content: Option<Buffer>,
+    extra_content: Option<&str>,
     tooltip: Tooltip,
     extra_classes: &[String],
 ) {
+    use super::format::write_str as write;
+
     write!(
         out,
         "<div class=\"example-wrap{}\">",
@@ -96,7 +98,7 @@ fn write_header(
     }
 
     if let Some(extra) = extra_content {
-        out.push_buffer(extra);
+        out.push_str(&extra);
     }
     if class.is_empty() {
         write!(
@@ -322,7 +324,8 @@ pub(super) fn write_code(
     });
 }
 
-fn write_footer(out: &mut Buffer, playground_button: Option<&str>) {
+fn write_footer(out: &mut String, playground_button: Option<&str>) {
+    use super::format::writeln_str as writeln;
     writeln!(out, "</code></pre>{}</div>", playground_button.unwrap_or_default());
 }
 

src/librustdoc/html/highlight/tests.rs

@@ -3,7 +3,6 @@ use rustc_data_structures::fx::FxIndexMap;
 use rustc_span::create_default_session_globals_then;
 
 use super::{DecorationInfo, write_code};
-use crate::html::format::Buffer;
 
 const STYLE: &str = r#"
 <style>
@@ -22,9 +21,9 @@ fn test_html_highlighting() {
     create_default_session_globals_then(|| {
         let src = include_str!("fixtures/sample.rs");
         let html = {
-            let mut out = Buffer::new();
+            let mut out = String::new();
             write_code(&mut out, src, None, None);
-            format!("{STYLE}<pre><code>{}</code></pre>\n", out.into_inner())
+            format!("{STYLE}<pre><code>{out}</code></pre>\n")
         };
         expect_file!["fixtures/sample.html"].assert_eq(&html);
     });
@@ -36,9 +35,9 @@ fn test_dos_backline() {
         let src = "pub fn foo() {\r\n\
     println!(\"foo\");\r\n\
 }\r\n";
-        let mut html = Buffer::new();
+        let mut html = String::new();
         write_code(&mut html, src, None, None);
-        expect_file!["fixtures/dos_line.html"].assert_eq(&html.into_inner());
+        expect_file!["fixtures/dos_line.html"].assert_eq(&html);
     });
 }
 
@@ -50,19 +49,19 @@ use self::whatever;
 let x = super::b::foo;
 let y = Self::whatever;";
 
-        let mut html = Buffer::new();
+        let mut html = String::new();
         write_code(&mut html, src, None, None);
-        expect_file!["fixtures/highlight.html"].assert_eq(&html.into_inner());
+        expect_file!["fixtures/highlight.html"].assert_eq(&html);
     });
 }
 
 #[test]
 fn test_union_highlighting() {
     create_default_session_globals_then(|| {
         let src = include_str!("fixtures/union.rs");
-        let mut html = Buffer::new();
+        let mut html = String::new();
         write_code(&mut html, src, None, None);
-        expect_file!["fixtures/union.html"].assert_eq(&html.into_inner());
+        expect_file!["fixtures/union.html"].assert_eq(&html);
     });
 }
 
@@ -77,8 +76,8 @@ let a = 4;";
         decorations.insert("example", vec![(0, 10), (11, 21)]);
         decorations.insert("example2", vec![(22, 32)]);
 
-        let mut html = Buffer::new();
+        let mut html = String::new();
         write_code(&mut html, src, None, Some(&DecorationInfo(decorations)));
-        expect_file!["fixtures/decorations.html"].assert_eq(&html.into_inner());
+        expect_file!["fixtures/decorations.html"].assert_eq(&html);
     });
 }

src/librustdoc/html/layout.rs

@@ -1,11 +1,11 @@
+use std::fmt::{self, Display};
 use std::path::PathBuf;
 
 use rinja::Template;
 use rustc_data_structures::fx::FxIndexMap;
 
 use super::static_files::{STATIC_FILES, StaticFiles};
 use crate::externalfiles::ExternalHtml;
-use crate::html::format::{Buffer, Print};
 use crate::html::render::{StylePath, ensure_trailing_slash};
 
 #[derive(Clone)]
@@ -71,7 +71,24 @@ struct PageLayout<'a> {
 
 pub(crate) use crate::html::render::sidebar::filters;
 
-pub(crate) fn render<T: Print, S: Print>(
+/// Implements [`Display`] for a function that accepts a mutable reference to a [`String`], and (optionally) writes to it.
+///
+/// The wrapped function will receive an empty string, and can modify it,
+/// and the `Display` implementation will write the contents of the string after the function has finished.
+pub(crate) struct BufDisplay<F>(pub F);
+
+impl<F> Display for BufDisplay<F>
+where
+    F: Fn(&mut String),
+{
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let mut buf = String::new();
+        self.0(&mut buf);
+        f.write_str(&buf)
+    }
+}
+
+pub(crate) fn render<T: Display, S: Display>(
     layout: &Layout,
     page: &Page<'_>,
     sidebar: S,
@@ -98,8 +115,8 @@ pub(crate) fn render<T: Print, S: Print>(
     let mut themes: Vec<String> = style_files.iter().map(|s| s.basename().unwrap()).collect();
     themes.sort();
 
-    let content = Buffer::html().to_display(t); // Note: This must happen before making the sidebar.
-    let sidebar = Buffer::html().to_display(sidebar);
+    let content = t.to_string(); // Note: This must happen before making the sidebar.
+    let sidebar = sidebar.to_string();
     PageLayout {
         static_root_path,
         page,

src/librustdoc/html/markdown.rs

@@ -52,7 +52,6 @@ use crate::clean::RenderedLink;
 use crate::doctest;
 use crate::doctest::GlobalTestOptions;
 use crate::html::escape::{Escape, EscapeBodyText};
-use crate::html::format::Buffer;
 use crate::html::highlight;
 use crate::html::length_limit::HtmlWithLimit;
 use crate::html::render::small_url_encode;
@@ -329,7 +328,7 @@ impl<'a, I: Iterator<Item = Event<'a>>> Iterator for CodeBlocks<'_, 'a, I> {
 
         // insert newline to clearly separate it from the
         // previous block so we can shorten the html output
-        let mut s = Buffer::new();
+        let mut s = String::new();
         s.push('\n');
 
         highlight::render_example_with_highlighting(
@@ -339,7 +338,7 @@ impl<'a, I: Iterator<Item = Event<'a>>> Iterator for CodeBlocks<'_, 'a, I> {
             playground_button.as_deref(),
             &added_classes,
         );
-        Some(Event::Html(s.into_inner().into()))
+        Some(Event::Html(s.into()))
     }
 }