Merge pull request #1007 from kamalmarhubi/basic-line-ranges-v2

Add infrastructure for formatting specific line ranges

Cargo.lock

@@ -7,6 +7,7 @@ dependencies = [
  "getopts 0.2.14 (registry+https://github.com/rust-lang/crates.io-index)",
  "itertools 0.4.15 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "multimap 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "regex 0.1.71 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-serialize 0.3.19 (registry+https://github.com/rust-lang/crates.io-index)",
  "strings 0.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -80,6 +81,11 @@ dependencies = [
  "libc 0.2.11 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "multimap"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "regex"
 version = "0.1.71"

Cargo.toml

@@ -26,3 +26,4 @@ log = "0.3"
 env_logger = "0.3"
 getopts = "0.2"
 itertools = "0.4.15"
+multimap = "0.3"

README.md

@@ -73,6 +73,25 @@ the command line. For example `rustfmt --write-mode=display src/filename.rs`
 
 `cargo fmt` uses `--write-mode=replace` by default.
 
+If you want to restrict reformatting to specific sets of lines, you can
+use the `--file-lines` option. Its argument is a JSON array of objects
+with `file` and `range` properties, where `file` is a file name, and
+`range` is an array representing a range of lines like `[7,13]`. Ranges
+are 1-based and inclusive of both end points. Specifying an empty array
+will result in no files being formatted. For example,
+
+```
+rustfmt --file-lines '[
+    {"file":"src/lib.rs","range":[7,13]},
+    {"file":"src/lib.rs","range":[21,29]},
+    {"file":"src/foo.rs","range":[10,11]},
+    {"file":"src/foo.rs","range":[15,15]}]'
+```
+
+would format lines `7-13` and `21-29` of `src/lib.rs`, and lines `10-11`,
+and `15` of `src/foo.rs`. No other files would be formatted, even if they
+are included as out of line modules from `src/lib.rs`.
+
 If `rustfmt` successfully reformatted the code it will exit with `0` exit
 status. Exit status `1` signals some unexpected error, like an unknown option or
 a failure to read a file. Exit status `2` is returned if there are syntax errors

src/bin/rustfmt.rs

@@ -18,6 +18,7 @@ extern crate env_logger;
 extern crate getopts;
 
 use rustfmt::{run, Input, Summary};
+use rustfmt::file_lines::FileLines;
 use rustfmt::config::{Config, WriteMode};
 
 use std::{env, error};
@@ -57,6 +58,7 @@ struct CliOptions {
     skip_children: bool,
     verbose: bool,
     write_mode: Option<WriteMode>,
+    file_lines: FileLines, // Default is all lines in all files.
 }
 
 impl CliOptions {
@@ -73,12 +75,17 @@ impl CliOptions {
             }
         }
 
+        if let Some(ref file_lines) = matches.opt_str("file-lines") {
+            options.file_lines = try!(file_lines.parse());
+        }
+
         Ok(options)
     }
 
-    fn apply_to(&self, config: &mut Config) {
+    fn apply_to(self, config: &mut Config) {
         config.skip_children = self.skip_children;
         config.verbose = self.verbose;
+        config.file_lines = self.file_lines;
         if let Some(write_mode) = self.write_mode {
             config.write_mode = write_mode;
         }
@@ -168,6 +175,10 @@ fn make_opts() -> Options {
                 "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]");
+    opts.optopt("",
+                "file-lines",
+                "Format specified line ranges. See README for more detail on the JSON format.",
+                "JSON");
 
     opts
 }
@@ -198,8 +209,12 @@ fn execute(opts: &Options) -> FmtResult<Summary> {
 
             Ok(run(Input::Text(input), &config))
         }
-        Operation::Format { files, config_path } => {
+        Operation::Format { mut files, config_path } => {
             let options = try!(CliOptions::from_matches(&matches));
+
+            // Add any additional files that were specified via `--file-lines`.
+            files.extend(options.file_lines.files().cloned().map(PathBuf::from));
+
             let mut config = Config::default();
             let mut path = None;
             // Load the config path file if provided
@@ -227,7 +242,7 @@ fn execute(opts: &Options) -> FmtResult<Summary> {
                     config = config_tmp;
                 }
 
-                options.apply_to(&mut config);
+                options.clone().apply_to(&mut config);
                 error_summary.add(run(Input::File(file), &config));
             }
             Ok(error_summary)
@@ -306,8 +321,8 @@ fn determine_operation(matches: &Matches) -> FmtResult<Operation> {
             Some(dir)
         });
 
-    // if no file argument is supplied, read from stdin
-    if matches.free.is_empty() {
+    // if no file argument is supplied and `--file-lines` is not specified, read from stdin
+    if matches.free.is_empty() && !matches.opt_present("file-lines") {
 
         let mut buffer = String::new();
         try!(io::stdin().read_to_string(&mut buffer));
@@ -318,6 +333,7 @@ fn determine_operation(matches: &Matches) -> FmtResult<Operation> {
         });
     }
 
+    // We append files from `--file-lines` later in `execute()`.
     let files: Vec<_> = matches.free.iter().map(PathBuf::from).collect();
 
     Ok(Operation::Format {

src/codemap.rs

@@ -0,0 +1,94 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! This module contains utilities that work with the `CodeMap` from libsyntax / syntex_syntax.
+//! This includes extension traits and methods for looking up spans and line ranges for AST nodes.
+
+use std::rc::Rc;
+
+use syntax::codemap::{BytePos, CodeMap, FileMap, Span};
+
+use comment::FindUncommented;
+
+/// A range of lines in a file, inclusive of both ends.
+pub struct LineRange {
+    pub file: Rc<FileMap>,
+    pub lo: usize,
+    pub hi: usize,
+}
+
+impl LineRange {
+    pub fn file_name(&self) -> &str {
+        self.file.as_ref().name.as_str()
+    }
+}
+
+pub trait SpanUtils {
+    fn span_after(&self, original: Span, needle: &str) -> BytePos;
+    fn span_after_last(&self, original: Span, needle: &str) -> BytePos;
+    fn span_before(&self, original: Span, needle: &str) -> BytePos;
+}
+
+pub trait LineRangeUtils {
+    /// Returns the `LineRange` that corresponds to `span` in `self`.
+    ///
+    /// # Panics
+    ///
+    /// Panics if `span` crosses a file boundary, which shouldn't happen.
+    fn lookup_line_range(&self, span: Span) -> LineRange;
+}
+
+impl SpanUtils for CodeMap {
+    #[inline]
+    fn span_after(&self, original: Span, needle: &str) -> BytePos {
+        let snippet = self.span_to_snippet(original).unwrap();
+        let offset = snippet.find_uncommented(needle).unwrap() + needle.len();
+
+        original.lo + BytePos(offset as u32)
+    }
+
+    #[inline]
+    fn span_after_last(&self, original: Span, needle: &str) -> BytePos {
+        let snippet = self.span_to_snippet(original).unwrap();
+        let mut offset = 0;
+
+        while let Some(additional_offset) = snippet[offset..].find_uncommented(needle) {
+            offset += additional_offset + needle.len();
+        }
+
+        original.lo + BytePos(offset as u32)
+    }
+
+    #[inline]
+    fn span_before(&self, original: Span, needle: &str) -> BytePos {
+        let snippet = self.span_to_snippet(original).unwrap();
+        let offset = snippet.find_uncommented(needle).unwrap();
+
+        original.lo + BytePos(offset as u32)
+    }
+}
+
+impl LineRangeUtils for CodeMap {
+    fn lookup_line_range(&self, span: Span) -> LineRange {
+        let lo = self.lookup_char_pos(span.lo);
+        let hi = self.lookup_char_pos(span.hi);
+
+        assert!(lo.file.name == hi.file.name,
+                "span crossed file boundary: lo: {:?}, hi: {:?}",
+                lo,
+                hi);
+
+        LineRange {
+            file: lo.file.clone(),
+            lo: lo.line,
+            hi: hi.line,
+        }
+    }
+}

src/config.rs

@@ -10,6 +10,7 @@
 
 extern crate toml;
 
+use file_lines::FileLines;
 use lists::{SeparatorTactic, ListTactic};
 use std::io::Write;
 
@@ -200,6 +201,12 @@ impl ConfigType for String {
     }
 }
 
+impl ConfigType for FileLines {
+    fn doc_hint() -> String {
+        String::from("<json>")
+    }
+}
+
 pub struct ConfigHelpItem {
     option_name: &'static str,
     doc_string: &'static str,
@@ -327,6 +334,9 @@ macro_rules! create_config {
 create_config! {
     verbose: bool, false, "Use verbose output";
     skip_children: bool, false, "Don't reformat out of line modules";
+    file_lines: FileLines, FileLines::all(),
+        "Lines to format; this is not supported in rustfmt.toml, and can only be specified \
+         via the --file-lines option";
     max_width: usize, 100, "Maximum width of each line";
     ideal_width: usize, 80, "Ideal width of each line";
     tab_spaces: usize, 4, "Number of spaces per tab";

src/expr.rs

@@ -16,12 +16,13 @@ use std::iter::ExactSizeIterator;
 use std::fmt::Write;
 
 use {Indent, Spanned};
+use codemap::SpanUtils;
 use rewrite::{Rewrite, RewriteContext};
 use lists::{write_list, itemize_list, ListFormatting, SeparatorTactic, ListTactic,
             DefinitiveListTactic, definitive_tactic, ListItem, format_item_list};
 use string::{StringFormat, rewrite_string};
-use utils::{CodeMapSpanUtils, extra_offset, last_line_width, wrap_str, binary_search,
-            first_line_width, semicolon_for_stmt, trimmed_last_line_width, left_most_sub_expr};
+use utils::{extra_offset, last_line_width, wrap_str, binary_search, first_line_width,
+            semicolon_for_stmt, trimmed_last_line_width, left_most_sub_expr};
 use visitor::FmtVisitor;
 use config::{Config, StructLitStyle, MultilineStyle, ElseIfBraceStyle, ControlBraceStyle};
 use comment::{FindUncommented, rewrite_comment, contains_comment, recover_comment_removed};

src/file_lines.rs

@@ -0,0 +1,232 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! This module contains types and functions to support formatting specific line ranges.
+use std::{cmp, iter, str};
+
+use itertools::Itertools;
+use multimap::MultiMap;
+use rustc_serialize::{self, json};
+
+use codemap::LineRange;
+
+/// A range that is inclusive of both ends.
+#[derive(Clone, Copy, Debug, Eq, PartialEq, RustcDecodable)]
+struct Range {
+    pub lo: usize,
+    pub hi: usize,
+}
+
+impl<'a> From<&'a LineRange> for Range {
+    fn from(range: &'a LineRange) -> Range {
+        Range::new(range.lo, range.hi)
+    }
+}
+
+impl Range {
+    fn new(lo: usize, hi: usize) -> Range {
+        Range { lo: lo, hi: hi }
+    }
+
+    fn is_empty(self) -> bool {
+        self.lo > self.hi
+    }
+
+    fn contains(self, other: Range) -> bool {
+        if other.is_empty() {
+            true
+        } else {
+            !self.is_empty() && self.lo <= other.lo && self.hi >= other.hi
+        }
+    }
+
+    fn intersects(self, other: Range) -> bool {
+        if self.is_empty() || other.is_empty() {
+            false
+        } else {
+            (self.lo <= other.hi && other.hi <= self.hi) ||
+            (other.lo <= self.hi && self.hi <= other.hi)
+        }
+    }
+
+    fn adjacent_to(self, other: Range) -> bool {
+        if self.is_empty() || other.is_empty() {
+            false
+        } else {
+            self.hi + 1 == other.lo || other.hi + 1 == self.lo
+        }
+    }
+
+    /// Returns a new `Range` with lines from `self` and `other` if they were adjacent or
+    /// intersect; returns `None` otherwise.
+    fn merge(self, other: Range) -> Option<Range> {
+        if self.adjacent_to(other) || self.intersects(other) {
+            Some(Range::new(cmp::min(self.lo, other.lo), cmp::max(self.hi, other.hi)))
+        } else {
+            None
+        }
+    }
+}
+
+/// A set of lines in files.
+///
+/// It is represented as a multimap keyed on file names, with values a collection of
+/// non-overlapping ranges sorted by their start point. An inner `None` is interpreted to mean all
+/// lines in all files.
+#[derive(Clone, Debug, Default)]
+pub struct FileLines(Option<MultiMap<String, Range>>);
+
+/// Normalizes the ranges so that the invariants for `FileLines` hold: ranges are non-overlapping,
+/// and ordered by their start point.
+fn normalize_ranges(map: &mut MultiMap<String, Range>) {
+    for (_, ranges) in map.iter_all_mut() {
+        ranges.sort_by_key(|x| x.lo);
+        let merged = ranges.drain(..).coalesce(|x, y| x.merge(y).ok_or((x, y))).collect();
+        *ranges = merged;
+    }
+}
+
+impl FileLines {
+    /// Creates a `FileLines` that contains all lines in all files.
+    pub fn all() -> FileLines {
+        FileLines(None)
+    }
+
+    /// Creates a `FileLines` from a `MultiMap`, ensuring that the invariants hold.
+    fn from_multimap(map: MultiMap<String, Range>) -> FileLines {
+        let mut map = map;
+        normalize_ranges(&mut map);
+        FileLines(Some(map))
+    }
+
+    /// Returns an iterator over the files contained in `self`.
+    pub fn files(&self) -> Files {
+        Files(self.0.as_ref().map(MultiMap::keys))
+    }
+
+    /// Returns true if `range` is fully contained in `self`.
+    pub fn contains(&self, range: &LineRange) -> bool {
+        let map = match self.0 {
+            // `None` means "all lines in all files".
+            None => return true,
+            Some(ref map) => map,
+        };
+
+        match map.get_vec(range.file_name()) {
+            None => false,
+            Some(ranges) => ranges.iter().any(|r| r.contains(Range::from(range))),
+        }
+    }
+
+    /// Returns true if any lines in `range` are in `self`.
+    pub fn intersects(&self, range: &LineRange) -> bool {
+        let map = match self.0 {
+            // `None` means "all lines in all files".
+            None => return true,
+            Some(ref map) => map,
+        };
+
+        match map.get_vec(range.file_name()) {
+            None => false,
+            Some(ranges) => ranges.iter().any(|r| r.intersects(Range::from(range))),
+        }
+    }
+}
+
+/// FileLines files iterator.
+pub struct Files<'a>(Option<::std::collections::hash_map::Keys<'a, String, Vec<Range>>>);
+
+impl<'a> iter::Iterator for Files<'a> {
+    type Item = &'a String;
+
+    fn next(&mut self) -> Option<&'a String> {
+        self.0.as_mut().and_then(Iterator::next)
+    }
+}
+
+// This impl is needed for `Config::override_value` to work for use in tests.
+impl str::FromStr for FileLines {
+    type Err = String;
+
+    fn from_str(s: &str) -> Result<FileLines, String> {
+        let v: Vec<JsonSpan> = try!(json::decode(s).map_err(|e| e.to_string()));
+        let m = v.into_iter().map(JsonSpan::into_tuple).collect();
+        Ok(FileLines::from_multimap(m))
+    }
+}
+
+// For JSON decoding.
+#[derive(Clone, Debug, RustcDecodable)]
+struct JsonSpan {
+    file: String,
+    range: (usize, usize),
+}
+
+impl JsonSpan {
+    // To allow `collect()`ing into a `MultiMap`.
+    fn into_tuple(self) -> (String, Range) {
+        let (lo, hi) = self.range;
+        (self.file, Range::new(lo, hi))
+    }
+}
+
+// This impl is needed for inclusion in the `Config` struct. We don't have a toml representation
+// for `FileLines`, so it will just panic instead.
+impl rustc_serialize::Decodable for FileLines {
+    fn decode<D: rustc_serialize::Decoder>(_: &mut D) -> Result<Self, D::Error> {
+        panic!("FileLines cannot be deserialized from a project rustfmt.toml file: please \
+                specify it via the `--file-lines` option instead");
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::Range;
+
+    #[test]
+    fn test_range_intersects() {
+        assert!(Range::new(1, 2).intersects(Range::new(1, 1)));
+        assert!(Range::new(1, 2).intersects(Range::new(2, 2)));
+        assert!(!Range::new(1, 2).intersects(Range::new(0, 0)));
+        assert!(!Range::new(1, 2).intersects(Range::new(3, 10)));
+        assert!(!Range::new(1, 3).intersects(Range::new(5, 5)));
+    }
+
+    #[test]
+    fn test_range_adjacent_to() {
+        assert!(!Range::new(1, 2).adjacent_to(Range::new(1, 1)));
+        assert!(!Range::new(1, 2).adjacent_to(Range::new(2, 2)));
+        assert!(Range::new(1, 2).adjacent_to(Range::new(0, 0)));
+        assert!(Range::new(1, 2).adjacent_to(Range::new(3, 10)));
+        assert!(!Range::new(1, 3).adjacent_to(Range::new(5, 5)));
+    }
+
+    #[test]
+    fn test_range_contains() {
+        assert!(Range::new(1, 2).contains(Range::new(1, 1)));
+        assert!(Range::new(1, 2).contains(Range::new(2, 2)));
+        assert!(!Range::new(1, 2).contains(Range::new(0, 0)));
+        assert!(!Range::new(1, 2).contains(Range::new(3, 10)));
+    }
+
+    #[test]
+    fn test_range_merge() {
+        assert_eq!(None, Range::new(1, 3).merge(Range::new(5, 5)));
+        assert_eq!(None, Range::new(4, 7).merge(Range::new(0, 1)));
+        assert_eq!(Some(Range::new(3, 7)),
+                   Range::new(3, 5).merge(Range::new(4, 7)));
+        assert_eq!(Some(Range::new(3, 7)),
+                   Range::new(3, 5).merge(Range::new(5, 7)));
+        assert_eq!(Some(Range::new(3, 7)),
+                   Range::new(3, 5).merge(Range::new(6, 7)));
+        assert_eq!(Some(Range::new(3, 7)),
+                   Range::new(3, 7).merge(Range::new(4, 5)));
+    }
+}

src/imports.rs

@@ -9,9 +9,9 @@
 // except according to those terms.
 
 use Indent;
+use codemap::SpanUtils;
 use lists::{write_list, itemize_list, ListItem, ListFormatting, SeparatorTactic, definitive_tactic};
 use types::rewrite_path;
-use utils::CodeMapSpanUtils;
 use rewrite::{Rewrite, RewriteContext};
 
 use syntax::ast;

src/items.rs

@@ -11,8 +11,9 @@
 // Formatting top-level items - functions, structs, enums, traits, impls.
 
 use Indent;
-use utils::{CodeMapSpanUtils, format_mutability, format_visibility, contains_skip, end_typaram,
-            wrap_str, last_line_width, semicolon_for_expr, format_unsafety, trim_newlines};
+use codemap::SpanUtils;
+use utils::{format_mutability, format_visibility, contains_skip, end_typaram, wrap_str,
+            last_line_width, semicolon_for_expr, format_unsafety, trim_newlines};
 use lists::{write_list, itemize_list, ListItem, ListFormatting, SeparatorTactic,
             DefinitiveListTactic, ListTactic, definitive_tactic, format_item_list};
 use expr::{is_empty_block, is_simple_block_stmt, rewrite_assign_rhs};

src/lib.rs

@@ -25,6 +25,7 @@ extern crate regex;
 extern crate diff;
 extern crate term;
 extern crate itertools;
+extern crate multimap;
 
 use syntax::ast;
 use syntax::codemap::{mk_sp, CodeMap, Span};
@@ -52,7 +53,9 @@ pub use self::summary::Summary;
 #[macro_use]
 mod utils;
 pub mod config;
+pub mod codemap;
 pub mod filemap;
+pub mod file_lines;
 pub mod visitor;
 mod checkstyle;
 mod items;
@@ -470,6 +473,7 @@ pub fn format_input<T: Write>(input: Input,
     }
 }
 
+#[derive(Debug)]
 pub enum Input {
     File(PathBuf),
     Text(String),

src/macros.rs

@@ -25,10 +25,11 @@ use syntax::parse::tts_to_parser;
 use syntax::codemap::{mk_sp, BytePos};
 
 use Indent;
+use codemap::SpanUtils;
 use rewrite::{Rewrite, RewriteContext};
 use expr::{rewrite_call, rewrite_array};
 use comment::{FindUncommented, contains_comment};
-use utils::{CodeMapSpanUtils, wrap_str};
+use utils::wrap_str;
 
 const FORCED_BRACKET_MACROS: &'static [&'static str] = &["vec!"];
 

src/patterns.rs

@@ -9,8 +9,9 @@
 // except according to those terms.
 
 use Indent;
+use codemap::SpanUtils;
 use rewrite::{Rewrite, RewriteContext};
-use utils::{CodeMapSpanUtils, wrap_str, format_mutability};
+use utils::{wrap_str, format_mutability};
 use lists::{format_item_list, itemize_list};
 use expr::{rewrite_unary_prefix, rewrite_pair, rewrite_tuple};
 use types::rewrite_path;

src/types.rs

@@ -17,9 +17,10 @@ use syntax::codemap::{self, Span, BytePos};
 use syntax::abi;
 
 use {Indent, Spanned};
+use codemap::SpanUtils;
 use lists::{format_item_list, itemize_list, format_fn_args};
 use rewrite::{Rewrite, RewriteContext};
-use utils::{CodeMapSpanUtils, extra_offset, format_mutability, wrap_str};
+use utils::{extra_offset, format_mutability, wrap_str};
 use expr::{rewrite_unary_prefix, rewrite_pair, rewrite_tuple};
 use config::TypeDensity;
 

src/utils.rs

@@ -14,51 +14,14 @@ use std::cmp::Ordering;
 use itertools::Itertools;
 
 use syntax::ast::{self, Visibility, Attribute, MetaItem, MetaItemKind, Path};
-use syntax::codemap::{CodeMap, Span, BytePos};
+use syntax::codemap::BytePos;
 use syntax::abi;
 
 use Indent;
-use comment::FindUncommented;
 use rewrite::{Rewrite, RewriteContext};
 
 use SKIP_ANNOTATION;
 
-pub trait CodeMapSpanUtils {
-    fn span_after(&self, original: Span, needle: &str) -> BytePos;
-    fn span_after_last(&self, original: Span, needle: &str) -> BytePos;
-    fn span_before(&self, original: Span, needle: &str) -> BytePos;
-}
-
-impl CodeMapSpanUtils for CodeMap {
-    #[inline]
-    fn span_after(&self, original: Span, needle: &str) -> BytePos {
-        let snippet = self.span_to_snippet(original).unwrap();
-        let offset = snippet.find_uncommented(needle).unwrap() + needle.len();
-
-        original.lo + BytePos(offset as u32)
-    }
-
-    #[inline]
-    fn span_after_last(&self, original: Span, needle: &str) -> BytePos {
-        let snippet = self.span_to_snippet(original).unwrap();
-        let mut offset = 0;
-
-        while let Some(additional_offset) = snippet[offset..].find_uncommented(needle) {
-            offset += additional_offset + needle.len();
-        }
-
-        original.lo + BytePos(offset as u32)
-    }
-
-    #[inline]
-    fn span_before(&self, original: Span, needle: &str) -> BytePos {
-        let snippet = self.span_to_snippet(original).unwrap();
-        let offset = snippet.find_uncommented(needle).unwrap();
-
-        original.lo + BytePos(offset as u32)
-    }
-}
-
 // Computes the length of a string's last line, minus offset.
 #[inline]
 pub fn extra_offset(text: &str, offset: Indent) -> usize {

src/visitor.rs

@@ -15,7 +15,8 @@ use syntax::parse::ParseSess;
 use strings::string_buffer::StringBuffer;
 
 use Indent;
-use utils::{self, CodeMapSpanUtils};
+use utils;
+use codemap::{LineRangeUtils, SpanUtils};
 use config::Config;
 use rewrite::{Rewrite, RewriteContext};
 use comment::rewrite_comment;
@@ -42,6 +43,15 @@ pub struct FmtVisitor<'a> {
 
 impl<'a> FmtVisitor<'a> {
     fn visit_stmt(&mut self, stmt: &ast::Stmt) {
+        debug!("visit_stmt: {:?} {:?}",
+               self.codemap.lookup_char_pos(stmt.span.lo),
+               self.codemap.lookup_char_pos(stmt.span.hi));
+
+        // FIXME(#434): Move this check to somewhere more central, eg Rewrite.
+        if !self.config.file_lines.contains(&self.codemap.lookup_line_range(stmt.span)) {
+            return;
+        }
+
         match stmt.node {
             ast::StmtKind::Decl(ref decl, _) => {
                 if let ast::DeclKind::Item(ref item) = decl.node {

tests/source/file-lines-1.rs

@@ -0,0 +1,29 @@
+// rustfmt-file_lines: [{"file":"tests/source/file-lines-1.rs","range":[4,8]}]
+
+fn floaters() {
+    let x = Foo {
+                field1: val1,
+                field2: val2,
+            }
+            .method_call().method_call();
+
+    let y = if cond {
+                val1
+            } else {
+                val2
+            }
+                .method_call();
+
+    {
+        match x {
+            PushParam => {
+                // params are 1-indexed
+                stack.push(mparams[match cur.to_digit(10) {
+                                            Some(d) => d as usize - 1,
+                                            None => return Err("bad param number".to_owned()),
+                                        }]
+                               .clone());
+            }
+        }
+    }
+}

tests/source/file-lines-2.rs

@@ -0,0 +1,29 @@
+// rustfmt-file_lines: [{"file":"tests/source/file-lines-2.rs","range":[10,15]}]
+
+fn floaters() {
+    let x = Foo {
+                field1: val1,
+                field2: val2,
+            }
+            .method_call().method_call();
+
+    let y = if cond {
+                val1
+            } else {
+                val2
+            }
+            .method_call();
+
+    {
+        match x {
+            PushParam => {
+                // params are 1-indexed
+                stack.push(mparams[match cur.to_digit(10) {
+                                            Some(d) => d as usize - 1,
+                                            None => return Err("bad param number".to_owned()),
+                                        }]
+                               .clone());
+            }
+        }
+    }
+}

tests/source/file-lines-3.rs

@@ -0,0 +1,29 @@
+// rustfmt-file_lines: [{"file":"tests/source/file-lines-3.rs","range":[4,8]},{"file":"tests/source/file-lines-3.rs","range":[10,15]}]
+
+fn floaters() {
+    let x = Foo {
+                field1: val1,
+                field2: val2,
+            }
+            .method_call().method_call();
+
+    let y = if cond {
+                val1
+            } else {
+                val2
+            }
+                .method_call();
+
+    {
+        match x {
+            PushParam => {
+                // params are 1-indexed
+                stack.push(mparams[match cur.to_digit(10) {
+                                            Some(d) => d as usize - 1,
+                                            None => return Err("bad param number".to_owned()),
+                                        }]
+                               .clone());
+            }
+        }
+    }
+}

tests/source/file-lines-4.rs

@@ -0,0 +1,30 @@
+// rustfmt-file_lines: []
+// (Test that nothing is formatted if an empty array is specified.)
+
+fn floaters() {
+    let x = Foo {
+                field1: val1,
+                field2: val2,
+            }
+            .method_call().method_call();
+
+    let y = if cond {
+                val1
+            } else {
+                val2
+            }
+                .method_call();
+
+    {
+        match x {
+            PushParam => {
+                // params are 1-indexed
+                stack.push(mparams[match cur.to_digit(10) {
+                                            Some(d) => d as usize - 1,
+                                            None => return Err("bad param number".to_owned()),
+                                        }]
+                               .clone());
+            }
+        }
+    }
+}

tests/target/file-lines-1.rs

@@ -0,0 +1,30 @@
+// rustfmt-file_lines: [{"file":"tests/source/file-lines-1.rs","range":[4,8]}]
+
+fn floaters() {
+    let x = Foo {
+            field1: val1,
+            field2: val2,
+        }
+        .method_call()
+        .method_call();
+
+    let y = if cond {
+                val1
+            } else {
+                val2
+            }
+                .method_call();
+
+    {
+        match x {
+            PushParam => {
+                // params are 1-indexed
+                stack.push(mparams[match cur.to_digit(10) {
+                                            Some(d) => d as usize - 1,
+                                            None => return Err("bad param number".to_owned()),
+                                        }]
+                               .clone());
+            }
+        }
+    }
+}

tests/target/file-lines-2.rs

@@ -0,0 +1,24 @@
+// rustfmt-file_lines: [{"file":"tests/source/file-lines-2.rs","range":[10,15]}]
+
+fn floaters() {
+    let x = Foo {
+                field1: val1,
+                field2: val2,
+            }
+            .method_call().method_call();
+
+    let y = if cond { val1 } else { val2 }.method_call();
+
+    {
+        match x {
+            PushParam => {
+                // params are 1-indexed
+                stack.push(mparams[match cur.to_digit(10) {
+                                            Some(d) => d as usize - 1,
+                                            None => return Err("bad param number".to_owned()),
+                                        }]
+                               .clone());
+            }
+        }
+    }
+}

tests/target/file-lines-3.rs

@@ -0,0 +1,25 @@
+// rustfmt-file_lines: [{"file":"tests/source/file-lines-3.rs","range":[4,8]},{"file":"tests/source/file-lines-3.rs","range":[10,15]}]
+
+fn floaters() {
+    let x = Foo {
+            field1: val1,
+            field2: val2,
+        }
+        .method_call()
+        .method_call();
+
+    let y = if cond { val1 } else { val2 }.method_call();
+
+    {
+        match x {
+            PushParam => {
+                // params are 1-indexed
+                stack.push(mparams[match cur.to_digit(10) {
+                                            Some(d) => d as usize - 1,
+                                            None => return Err("bad param number".to_owned()),
+                                        }]
+                               .clone());
+            }
+        }
+    }
+}

tests/target/file-lines-4.rs

@@ -0,0 +1,30 @@
+// rustfmt-file_lines: []
+// (Test that nothing is formatted if an empty array is specified.)
+
+fn floaters() {
+    let x = Foo {
+                field1: val1,
+                field2: val2,
+            }
+            .method_call().method_call();
+
+    let y = if cond {
+                val1
+            } else {
+                val2
+            }
+                .method_call();
+
+    {
+        match x {
+            PushParam => {
+                // params are 1-indexed
+                stack.push(mparams[match cur.to_digit(10) {
+                                            Some(d) => d as usize - 1,
+                                            None => return Err("bad param number".to_owned()),
+                                        }]
+                               .clone());
+            }
+        }
+    }
+}