rustfmt: Add an ineffectual --file-lines flag behind a feature

This adds a `--file-lines` flag that is behind the Cargo feature
`experimental-file-lines`. The argument is parsed and propagated, but so
far it is only an alternative and verbose way to specify files and set
`skip_children`.

Refs https://github.com/nrc/rustfmt/issues/434

Cargo.toml

@@ -12,6 +12,9 @@ include = ["src/*.rs", "Cargo.toml"]
 [features]
 default = ["cargo-fmt"]
 cargo-fmt = []
+# Feature for the in-development --file-lines argument, limiting formatting to
+# specified line ranges.
+experimental-file-lines = ["nom"]
 
 [dependencies]
 toml = "0.1.20"
@@ -25,3 +28,5 @@ syntex_syntax = "0.23.0"
 log = "0.3.2"
 env_logger = "0.3.1"
 getopts = "0.2"
+cfg-if = "0.1.0"
+nom = { version = "1.2.1", optional = true }

src/bin/rustfmt.rs

@@ -10,15 +10,23 @@
 
 #![cfg(not(test))]
 
+#[macro_use]
+extern crate cfg_if;
 #[macro_use]
 extern crate log;
+#[cfg(feature = "experimental-file-lines")]
+#[macro_use]
+extern crate nom;
+
 extern crate rustfmt;
 extern crate toml;
 extern crate env_logger;
 extern crate getopts;
 
 use rustfmt::{run, run_from_stdin};
 use rustfmt::config::{Config, WriteMode};
+#[cfg(feature = "experimental-file-lines")]
+use rustfmt::config::FileLinesMap;
 
 use std::env;
 use std::fs::{self, File};
@@ -42,6 +50,11 @@ enum Operation {
     InvalidInput(String),
     /// No file specified, read from stdin
     Stdin(String, Option<PathBuf>),
+    /// Format a set of line ranges.
+    #[cfg(feature = "experimental-file-lines")]
+    FormatLineRanges {
+        file_lines_map: FileLinesMap,
+    },
 }
 
 /// Try to find a project file in the given directory and its parents. Returns the path of a the
@@ -112,7 +125,9 @@ fn match_cli_path_or_file(config_path: Option<PathBuf>,
 
 fn update_config(config: &mut Config, matches: &Matches) -> Result<(), String> {
     config.verbose = matches.opt_present("verbose");
-    config.skip_children = matches.opt_present("skip-children");
+    // `file-lines` implies `skip-children`.
+    config.skip_children = matches.opt_present("skip-children") ||
+                           matches.opt_present("file-lines");
 
     let write_mode = matches.opt_str("write-mode");
     match matches.opt_str("write-mode").map(|wm| WriteMode::from_str(&wm)) {
@@ -144,6 +159,13 @@ fn execute() -> i32 {
                 "Recursively searches the given path for the rustfmt.toml config file. If not \
                  found reverts to the input file path",
                 "[Path for the configuration file]");
+    if cfg!(feature = "experimental-file-lines") {
+        opts.optmulti("",
+                      "file-lines",
+                      "Format specified line RANGEs in FILENAME. RANGEs are inclusive of both \
+                       endpoints. May be specified multiple times.",
+                      "FILENAME:RANGE,RANGE,...");
+    }
 
     let matches = match opts.parse(env::args().skip(1)) {
         Ok(m) => m,
@@ -220,6 +242,28 @@ fn execute() -> i32 {
             }
             0
         }
+        #[cfg(feature = "experimental-file-lines")]
+        // TODO: figure out what to do with config_path.
+        Operation::FormatLineRanges { file_lines_map } => {
+            for (file, line_ranges) in file_lines_map {
+                let (mut config, config_path) = resolve_config(file.parent().unwrap())
+                                                    .expect(&format!("Error resolving config \
+                                                                      for {}",
+                                                                     file.display()));
+                if let Some(path) = config_path.as_ref() {
+                    println!("Using rustfmt config file {} for {}",
+                             path.display(),
+                             file.display());
+                }
+                if let Err(e) = update_config(&mut config, &matches) {
+                    print_usage(&opts, &e);
+                    return 1;
+                }
+                config.line_ranges = line_ranges;
+                run(&file, &config);
+            }
+            0
+        }
     }
 }
 
@@ -275,6 +319,47 @@ fn determine_operation(matches: &Matches) -> Operation {
                                                   Some(dir)
                                               });
 
+    if matches.opt_present("file-lines") {
+        cfg_if! {
+            if #[cfg(feature = "experimental-file-lines")] {
+                fn handle_file_lines(args: &[String]) -> Operation {
+                    use rustfmt::config::{FileLinesMap, LineRanges};
+
+                    use nom::IResult;
+
+                    let mut file_lines_map = FileLinesMap::new();
+                    for range_spec in args {
+                        let res = parse::file_lines_arg(range_spec);
+
+                        let invalid = || {
+                            Operation::InvalidInput(format!("invalid file-lines argument: {}",
+                                                            range_spec))
+                        };
+
+                        let (file, line_ranges) = match res {
+                            IResult::Error(_) => return invalid(),
+                            IResult::Incomplete(_) => return invalid(),
+                            IResult::Done(remaining, _) if !remaining.is_empty() => {
+                                return invalid()
+                            }
+                            IResult::Done(_, (file, line_ranges)) => (file, line_ranges),
+                        };
+
+                        let entry = file_lines_map.entry(file).or_insert(LineRanges(Vec::new()));
+                        entry.0.extend(line_ranges.0);
+                    }
+                    return Operation::FormatLineRanges { file_lines_map: file_lines_map };
+                }
+            } else {
+                fn handle_file_lines(_: &[String]) -> ! {
+                    unimplemented!();
+                }
+            }
+        }
+
+        return handle_file_lines(&matches.opt_strs("file-lines"));
+    }
+
     // if no file argument is supplied, read from stdin
     if matches.free.is_empty() {
 
@@ -291,3 +376,60 @@ fn determine_operation(matches: &Matches) -> Operation {
 
     Operation::Format(files, config_path)
 }
+
+
+/// Parser for the `file-lines` argument.
+#[cfg(feature = "experimental-file-lines")]
+mod parse {
+    use std::path::PathBuf;
+    use std::str::FromStr;
+    use rustfmt::config::{LineRange, LineRanges};
+
+    use nom::digit;
+
+    named!(pub file_lines_arg<&str, (PathBuf, LineRanges)>,
+           chain!(
+               file: map!(
+                   is_not_s!(":"),
+                   PathBuf::from
+               ) ~
+               tag_s!(":") ~
+               line_ranges: line_ranges,
+               || (file, line_ranges)
+           )
+    );
+
+    named!(usize_digit<&str, usize>,
+           map_res!(
+               digit,
+               FromStr::from_str
+           )
+    );
+
+    named!(line_range<&str, LineRange>,
+           map_res!(
+               separated_pair!(
+                   usize_digit,
+                   tag_s!("-"),
+                   usize_digit
+               ),
+               |pair: (usize, usize)| {
+                   let (start, end) = pair;
+                   if end < start {
+                       return Err(format!("empty line range: {}-{}", start, end));
+                   }
+                   Ok(pair)
+               }
+           )
+    );
+
+    named!(line_ranges<&str, LineRanges>,
+           map!(
+               separated_nonempty_list!(
+                   tag_s!(","),
+                   line_range
+               ),
+               LineRanges
+           )
+    );
+}