1 files changed, 281 insertions, 0 deletions
diff --git a/src/tools/rustfmt/src/format-diff/main.rs b/src/tools/rustfmt/src/format-diff/main.rs
new file mode 100644
index 000000000..f6b739e1c
--- /dev/null
+++ b/src/tools/rustfmt/src/format-diff/main.rs
@@ -0,0 +1,281 @@
+// Inspired by Clang's clang-format-diff:
+//
+// https://github.com/llvm-mirror/clang/blob/master/tools/clang-format/clang-format-diff.py
+
+#![deny(warnings)]
+
+#[macro_use]
+extern crate log;
+
+use serde::{Deserialize, Serialize};
+use serde_json as json;
+use thiserror::Error;
+
+use std::collections::HashSet;
+use std::env;
+use std::ffi::OsStr;
+use std::io::{self, BufRead};
+use std::process;
+
+use regex::Regex;
+
+use clap::{CommandFactory, Parser};
+
+/// The default pattern of files to format.
+///
+/// We only want to format rust files by default.
+const DEFAULT_PATTERN: &str = r".*\.rs";
+
+#[derive(Error, Debug)]
+enum FormatDiffError {
+    #[error("{0}")]
+    IncorrectOptions(#[from] getopts::Fail),
+    #[error("{0}")]
+    IncorrectFilter(#[from] regex::Error),
+    #[error("{0}")]
+    IoError(#[from] io::Error),
+}
+
+#[derive(Parser, Debug)]
+#[clap(
+    name = "rustfmt-format-diff",
+    disable_version_flag = true,
+    next_line_help = true
+)]
+pub struct Opts {
+    /// Skip the smallest prefix containing NUMBER slashes
+    #[clap(
+        short = 'p',
+        long = "skip-prefix",
+        value_name = "NUMBER",
+        default_value = "0"
+    )]
+    skip_prefix: u32,
+
+    /// Custom pattern selecting file paths to reformat
+    #[clap(
+        short = 'f',
+        long = "filter",
+        value_name = "PATTERN",
+        default_value = DEFAULT_PATTERN
+    )]
+    filter: String,
+}
+
+fn main() {
+    env_logger::Builder::from_env("RUSTFMT_LOG").init();
+    let opts = Opts::parse();
+    if let Err(e) = run(opts) {
+        println!("{}", e);
+        Opts::command()
+            .print_help()
+            .expect("cannot write to stdout");
+        process::exit(1);
+    }
+}
+
+#[derive(Debug, Eq, PartialEq, Serialize, Deserialize)]
+struct Range {
+    file: String,
+    range: [u32; 2],
+}
+
+fn run(opts: Opts) -> Result<(), FormatDiffError> {
+    let (files, ranges) = scan_diff(io::stdin(), opts.skip_prefix, &opts.filter)?;
+    run_rustfmt(&files, &ranges)
+}
+
+fn run_rustfmt(files: &HashSet<String>, ranges: &[Range]) -> Result<(), FormatDiffError> {
+    if files.is_empty() || ranges.is_empty() {
+        debug!("No files to format found");
+        return Ok(());
+    }
+
+    let ranges_as_json = json::to_string(ranges).unwrap();
+
+    debug!("Files: {:?}", files);
+    debug!("Ranges: {:?}", ranges);
+
+    let rustfmt_var = env::var_os("RUSTFMT");
+    let rustfmt = match &rustfmt_var {
+        Some(rustfmt) => rustfmt,
+        None => OsStr::new("rustfmt"),
+    };
+    let exit_status = process::Command::new(rustfmt)
+        .args(files)
+        .arg("--file-lines")
+        .arg(ranges_as_json)
+        .status()?;
+
+    if !exit_status.success() {
+        return Err(FormatDiffError::IoError(io::Error::new(
+            io::ErrorKind::Other,
+            format!("rustfmt failed with {}", exit_status),
+        )));
+    }
+    Ok(())
+}
+
+/// Scans a diff from `from`, and returns the set of files found, and the ranges
+/// in those files.
+fn scan_diff<R>(
+    from: R,
+    skip_prefix: u32,
+    file_filter: &str,
+) -> Result<(HashSet<String>, Vec<Range>), FormatDiffError>
+where
+    R: io::Read,
+{
+    let diff_pattern = format!(r"^\+\+\+\s(?:.*?/){{{}}}(\S*)", skip_prefix);
+    let diff_pattern = Regex::new(&diff_pattern).unwrap();
+
+    let lines_pattern = Regex::new(r"^@@.*\+(\d+)(,(\d+))?").unwrap();
+
+    let file_filter = Regex::new(&format!("^{}$", file_filter))?;
+
+    let mut current_file = None;
+
+    let mut files = HashSet::new();
+    let mut ranges = vec![];
+    for line in io::BufReader::new(from).lines() {
+        let line = line.unwrap();
+
+        if let Some(captures) = diff_pattern.captures(&line) {
+            current_file = Some(captures.get(1).unwrap().as_str().to_owned());
+        }
+
+        let file = match current_file {
+            Some(ref f) => &**f,
+            None => continue,
+        };
+
+        // FIXME(emilio): We could avoid this most of the time if needed, but
+        // it's not clear it's worth it.
+        if !file_filter.is_match(file) {
+            continue;
+        }
+
+        let lines_captures = match lines_pattern.captures(&line) {
+            Some(captures) => captures,
+            None => continue,
+        };
+
+        let start_line = lines_captures
+            .get(1)
+            .unwrap()
+            .as_str()
+            .parse::<u32>()
+            .unwrap();
+        let line_count = match lines_captures.get(3) {
+            Some(line_count) => line_count.as_str().parse::<u32>().unwrap(),
+            None => 1,
+        };
+
+        if line_count == 0 {
+            continue;
+        }
+
+        let end_line = start_line + line_count - 1;
+        files.insert(file.to_owned());
+        ranges.push(Range {
+            file: file.to_owned(),
+            range: [start_line, end_line],
+        });
+    }
+
+    Ok((files, ranges))
+}
+
+#[test]
+fn scan_simple_git_diff() {
+    const DIFF: &str = include_str!("test/bindgen.diff");
+    let (files, ranges) = scan_diff(DIFF.as_bytes(), 1, r".*\.rs").expect("scan_diff failed?");
+
+    assert!(
+        files.contains("src/ir/traversal.rs"),
+        "Should've matched the filter"
+    );
+
+    assert!(
+        !files.contains("tests/headers/anon_enum.hpp"),
+        "Shouldn't have matched the filter"
+    );
+
+    assert_eq!(
+        &ranges,
+        &[
+            Range {
+                file: "src/ir/item.rs".to_owned(),
+                range: [148, 158],
+            },
+            Range {
+                file: "src/ir/item.rs".to_owned(),
+                range: [160, 170],
+            },
+            Range {
+                file: "src/ir/traversal.rs".to_owned(),
+                range: [9, 16],
+            },
+            Range {
+                file: "src/ir/traversal.rs".to_owned(),
+                range: [35, 43],
+            },
+        ]
+    );
+}
+
+#[cfg(test)]
+mod cmd_line_tests {
+    use super::*;
+
+    #[test]
+    fn default_options() {
+        let empty: Vec<String> = vec![];
+        let o = Opts::parse_from(&empty);
+        assert_eq!(DEFAULT_PATTERN, o.filter);
+        assert_eq!(0, o.skip_prefix);
+    }
+
+    #[test]
+    fn good_options() {
+        let o = Opts::parse_from(&["test", "-p", "10", "-f", r".*\.hs"]);
+        assert_eq!(r".*\.hs", o.filter);
+        assert_eq!(10, o.skip_prefix);
+    }
+
+    #[test]
+    fn unexpected_option() {
+        assert!(
+            Opts::command()
+                .try_get_matches_from(&["test", "unexpected"])
+                .is_err()
+        );
+    }
+
+    #[test]
+    fn unexpected_flag() {
+        assert!(
+            Opts::command()
+                .try_get_matches_from(&["test", "--flag"])
+                .is_err()
+        );
+    }
+
+    #[test]
+    fn overridden_option() {
+        assert!(
+            Opts::command()
+                .try_get_matches_from(&["test", "-p", "10", "-p", "20"])
+                .is_err()
+        );
+    }
+
+    #[test]
+    fn negative_filter() {
+        assert!(
+            Opts::command()
+                .try_get_matches_from(&["test", "-p", "-1"])
+                .is_err()
+        );
+    }
+}