crates: vendor annotate-snippets crate

This merely adds the crate to our repository. Some cosmetic changes are
made to make it work in our repo and follow our conventions, such as
changing the name to `ruff_annotate_snippets`. We retain the original
license information. We do drop some things, such as benchmarks, but
keep tests and examples.

crates/ruff_annotate_snippets/src/renderer/styled_buffer.rs

@@ -0,0 +1,97 @@
+//! Adapted from [styled_buffer]
+//!
+//! [styled_buffer]: https://github.com/rust-lang/rust/blob/894f7a4ba6554d3797404bbf550d9919df060b97/compiler/rustc_errors/src/styled_buffer.rs
+
+use crate::renderer::stylesheet::Stylesheet;
+use anstyle::Style;
+use std::fmt;
+use std::fmt::Write;
+
+#[derive(Debug)]
+pub(crate) struct StyledBuffer {
+    lines: Vec<Vec<StyledChar>>,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub(crate) struct StyledChar {
+    ch: char,
+    style: Style,
+}
+
+impl StyledChar {
+    pub(crate) const SPACE: Self = StyledChar::new(' ', Style::new());
+
+    pub(crate) const fn new(ch: char, style: Style) -> StyledChar {
+        StyledChar { ch, style }
+    }
+}
+
+impl StyledBuffer {
+    pub(crate) fn new() -> StyledBuffer {
+        StyledBuffer { lines: vec![] }
+    }
+
+    fn ensure_lines(&mut self, line: usize) {
+        if line >= self.lines.len() {
+            self.lines.resize(line + 1, Vec::new());
+        }
+    }
+
+    pub(crate) fn render(&self, stylesheet: &Stylesheet) -> Result<String, fmt::Error> {
+        let mut str = String::new();
+        for (i, line) in self.lines.iter().enumerate() {
+            let mut current_style = stylesheet.none;
+            for ch in line {
+                if ch.style != current_style {
+                    if !line.is_empty() {
+                        write!(str, "{}", current_style.render_reset())?;
+                    }
+                    current_style = ch.style;
+                    write!(str, "{}", current_style.render())?;
+                }
+                write!(str, "{}", ch.ch)?;
+            }
+            write!(str, "{}", current_style.render_reset())?;
+            if i != self.lines.len() - 1 {
+                writeln!(str)?;
+            }
+        }
+        Ok(str)
+    }
+
+    /// Sets `chr` with `style` for given `line`, `col`.
+    /// If `line` does not exist in our buffer, adds empty lines up to the given
+    /// and fills the last line with unstyled whitespace.
+    pub(crate) fn putc(&mut self, line: usize, col: usize, chr: char, style: Style) {
+        self.ensure_lines(line);
+        if col >= self.lines[line].len() {
+            self.lines[line].resize(col + 1, StyledChar::SPACE);
+        }
+        self.lines[line][col] = StyledChar::new(chr, style);
+    }
+
+    /// Sets `string` with `style` for given `line`, starting from `col`.
+    /// If `line` does not exist in our buffer, adds empty lines up to the given
+    /// and fills the last line with unstyled whitespace.
+    pub(crate) fn puts(&mut self, line: usize, col: usize, string: &str, style: Style) {
+        let mut n = col;
+        for c in string.chars() {
+            self.putc(line, n, c, style);
+            n += 1;
+        }
+    }
+    /// For given `line` inserts `string` with `style` after old content of that line,
+    /// adding lines if needed
+    pub(crate) fn append(&mut self, line: usize, string: &str, style: Style) {
+        if line >= self.lines.len() {
+            self.puts(line, 0, string, style);
+        } else {
+            let col = self.lines[line].len();
+            self.puts(line, col, string, style);
+        }
+    }
+
+    pub(crate) fn num_lines(&self) -> usize {
+        self.lines.len()
+    }
+}