Allow for setting of write-mode via config file. FIxes #215

Also from @marcusklaas:
 Refactor code output functions

 Specifically, `write_all_files` no longer returns a HashMap. It would sometimes
 contain items, and sometimes be empty. When "fixed" newlines are required, this
 must now be done with a separate call. The tests use this strategy and should now pass!

7 files changed, 97 insertions, 105 deletions

diff --git a/src/bin/rustfmt.rs b/src/bin/rustfmt.rs
index 3e369e1ef23..c795d529409 100644
--- a/src/bin/rustfmt.rs
+++ b/src/bin/rustfmt.rs
@@ -17,8 +17,8 @@ extern crate toml;
 extern crate env_logger;
 extern crate getopts;
 
-use rustfmt::{WriteMode, run, run_from_stdin};
-use rustfmt::config::Config;
+use rustfmt::{run, run_from_stdin};
+use rustfmt::config::{Config, WriteMode};
 
 use std::env;
 use std::fs::{self, File};
@@ -216,7 +216,7 @@ fn determine_operation(matches: &Matches) -> Operation {
                 Err(..) => return Operation::InvalidInput("Unrecognized write mode".into()),
             }
         }
-        None => WriteMode::Replace,
+        None => WriteMode::Default,
     };
 
     let files: Vec<_> = matches.free.iter().map(PathBuf::from).collect();
diff --git a/src/config.rs b/src/config.rs
index 7c8505e5e09..4576ecc5d2a 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -120,6 +120,24 @@ configuration_option_enum! { ReportTactic:
     Never,
 }
 
+configuration_option_enum! { WriteMode:
+    // Used internally to represent when no option is given
+    // Treated as Replace.
+    Default,
+    // Backsup the original file and overwrites the orignal.
+    Replace,
+    // Overwrites original file without backup.
+    Overwrite,
+    // Write the output to stdout.
+    Display,
+    // Write the diff to stdout.
+    Diff,
+    // Display how much of the input file was processed
+    Coverage,
+    // Unfancy stdout
+    Plain,
+}
+
 // This trait and the following impl blocks are there so that we an use
 // UCFS inside the get_docs() function on types for configs.
 pub trait ConfigType {
@@ -323,4 +341,6 @@ create_config! {
     match_block_trailing_comma: bool, false,
         "Put a trailing comma after a block based match arm (non-block arms are not affected)";
     match_wildcard_trailing_comma: bool, true, "Put a trailing comma after a wildcard arm";
+    write_mode: WriteMode, WriteMode::Default,
+        "What Write Mode to use when none is supplied: Replace, Overwrite, Display, Diff, Coverage";
 }
diff --git a/src/filemap.rs b/src/filemap.rs
index 95ae95e66bc..b518eaaa344 100644
--- a/src/filemap.rs
+++ b/src/filemap.rs
@@ -15,10 +15,9 @@ use strings::string_buffer::StringBuffer;
 
 use std::collections::HashMap;
 use std::fs::{self, File};
-use std::io::{self, Write, Read, stdout};
+use std::io::{self, Write, Read, stdout, BufWriter};
 
-use WriteMode;
-use config::{NewlineStyle, Config};
+use config::{NewlineStyle, Config, WriteMode};
 use rustfmt_diff::{make_diff, print_diff};
 
 // A map of the files of a crate, with their new content
@@ -34,56 +33,55 @@ pub fn append_newlines(file_map: &mut FileMap) {
 pub fn write_all_files(file_map: &FileMap,
                        mode: WriteMode,
                        config: &Config)
-                       -> Result<(HashMap<String, String>), io::Error> {
-    let mut result = HashMap::new();
+                       -> Result<(), io::Error> {
     for filename in file_map.keys() {
-        let one_result = try!(write_file(&file_map[filename], filename, mode, config));
-        if let Some(r) = one_result {
-            result.insert(filename.clone(), r);
-        }
+        try!(write_file(&file_map[filename], filename, mode, config));
     }
 
-    Ok(result)
+    Ok(())
 }
 
-pub fn write_file(text: &StringBuffer,
-                  filename: &str,
-                  mode: WriteMode,
-                  config: &Config)
-                  -> Result<Option<String>, io::Error> {
-
-    // prints all newlines either as `\n` or as `\r\n`
-    fn write_system_newlines<T>(mut writer: T,
+// Prints all newlines either as `\n` or as `\r\n`.
+pub fn write_system_newlines<T>(writer: T,
                                 text: &StringBuffer,
                                 config: &Config)
                                 -> Result<(), io::Error>
-        where T: Write
-    {
-        let style = if config.newline_style == NewlineStyle::Native {
-            if cfg!(windows) {
-                NewlineStyle::Windows
-            } else {
-                NewlineStyle::Unix
-            }
+    where T: Write
+{
+    // Buffer output, since we're writing a since char at a time.
+    let mut writer = BufWriter::new(writer);
+
+    let style = if config.newline_style == NewlineStyle::Native {
+        if cfg!(windows) {
+            NewlineStyle::Windows
         } else {
-            config.newline_style
-        };
-
-        match style {
-            NewlineStyle::Unix => write!(writer, "{}", text),
-            NewlineStyle::Windows => {
-                for (c, _) in text.chars() {
-                    match c {
-                        '\n' => try!(write!(writer, "\r\n")),
-                        '\r' => continue,
-                        c => try!(write!(writer, "{}", c)),
-                    }
+            NewlineStyle::Unix
+        }
+    } else {
+        config.newline_style
+    };
+
+    match style {
+        NewlineStyle::Unix => write!(writer, "{}", text),
+        NewlineStyle::Windows => {
+            for (c, _) in text.chars() {
+                match c {
+                    '\n' => try!(write!(writer, "\r\n")),
+                    '\r' => continue,
+                    c => try!(write!(writer, "{}", c)),
                 }
-                Ok(())
             }
-            NewlineStyle::Native => unreachable!(),
+            Ok(())
         }
+        NewlineStyle::Native => unreachable!(),
     }
+}
+
+pub fn write_file(text: &StringBuffer,
+                  filename: &str,
+                  mode: WriteMode,
+                  config: &Config)
+                  -> Result<Option<String>, io::Error> {
 
     fn source_and_formatted_text(text: &StringBuffer,
                                  filename: &str,
@@ -123,11 +121,6 @@ pub fn write_file(text: &StringBuffer,
             let file = try!(File::create(filename));
             try!(write_system_newlines(file, text, config));
         }
-        WriteMode::NewFile(extn) => {
-            let filename = filename.to_owned() + "." + extn;
-            let file = try!(File::create(&filename));
-            try!(write_system_newlines(file, text, config));
-        }
         WriteMode::Plain => {
             let stdout = stdout();
             let stdout = stdout.lock();
@@ -146,13 +139,8 @@ pub fn write_file(text: &StringBuffer,
                            |line_num| format!("\nDiff at line {}:", line_num));
             }
         }
-        WriteMode::Return => {
-            // io::Write is not implemented for String, working around with
-            // Vec<u8>
-            let mut v = Vec::new();
-            try!(write_system_newlines(&mut v, text, config));
-            // won't panic, we are writing correct utf8
-            return Ok(Some(String::from_utf8(v).unwrap()));
+        WriteMode::Default => {
+            unreachable!("The WriteMode should NEVER Be default at this point!");
         }
     }
 
diff --git a/src/lib.rs b/src/lib.rs
index 3ed7c3cad8c..fccc0f0934c 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -34,12 +34,11 @@ use std::ops::{Add, Sub};
 use std::path::Path;
 use std::collections::HashMap;
 use std::fmt;
-use std::str::FromStr;
 
 use issues::{BadIssueSeeker, Issue};
 use filemap::FileMap;
 use visitor::FmtVisitor;
-use config::Config;
+use config::{Config, WriteMode};
 
 #[macro_use]
 mod utils;
@@ -187,42 +186,6 @@ impl Sub<usize> for Indent {
     }
 }
 
-#[derive(Copy, Clone)]
-pub enum WriteMode {
-    // Backsup the original file and overwrites the orignal.
-    Replace,
-    // Overwrites original file without backup.
-    Overwrite,
-    // str is the extension of the new file.
-    NewFile(&'static str),
-    // Write the output to stdout.
-    Display,
-    // Write the diff to stdout.
-    Diff,
-    // Return the result as a mapping from filenames to Strings.
-    Return,
-    // Display how much of the input file was processed
-    Coverage,
-    // Unfancy stdout
-    Plain,
-}
-
-impl FromStr for WriteMode {
-    type Err = ();
-
-    fn from_str(s: &str) -> Result<Self, Self::Err> {
-        match s {
-            "replace" => Ok(WriteMode::Replace),
-            "display" => Ok(WriteMode::Display),
-            "overwrite" => Ok(WriteMode::Overwrite),
-            "diff" => Ok(WriteMode::Diff),
-            "coverage" => Ok(WriteMode::Coverage),
-            "plain" => Ok(WriteMode::Plain),
-            _ => Err(()),
-        }
-    }
-}
-
 pub enum ErrorKind {
     // Line has exceeded character limit
     LineOverflow,
@@ -445,16 +408,27 @@ pub fn format(file: &Path, config: &Config, mode: WriteMode) -> FileMap {
     file_map
 }
 
+// Make sure that we are using the correct WriteMode,
+// preferring what is passed as an argument
+fn check_write_mode(arg: WriteMode, config: WriteMode) -> WriteMode {
+    match (arg, config) {
+        (WriteMode::Default, WriteMode::Default) => WriteMode::Replace,
+        (WriteMode::Default, mode) => mode,
+        (mode, _) => mode,
+    }
+}
+
 // args are the arguments passed on the command line, generally passed through
 // to the compiler.
 // write_mode determines what happens to the result of running rustfmt, see
 // WriteMode.
 pub fn run(file: &Path, write_mode: WriteMode, config: &Config) {
-    let mut result = format(file, config, write_mode);
+    let mode = check_write_mode(write_mode, config.write_mode);
+    let mut result = format(file, config, mode);
 
     print!("{}", fmt_lines(&mut result, config));
 
-    let write_result = filemap::write_all_files(&result, write_mode, config);
+    let write_result = filemap::write_all_files(&result, mode, config);
 
     if let Err(msg) = write_result {
         println!("Error writing files: {}", msg);
@@ -462,7 +436,8 @@ pub fn run(file: &Path, write_mode: WriteMode, config: &Config) {
 }
 
 // Similar to run, but takes an input String instead of a file to format
-pub fn run_from_stdin(input: String, mode: WriteMode, config: &Config) {
+pub fn run_from_stdin(input: String, write_mode: WriteMode, config: &Config) {
+    let mode = check_write_mode(write_mode, config.write_mode);
     let mut result = format_string(input, config, mode);
     fmt_lines(&mut result, config);
 
diff --git a/src/missed_spans.rs b/src/missed_spans.rs
index 67661143ddf..cd69b6dcc80 100644
--- a/src/missed_spans.rs
+++ b/src/missed_spans.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use WriteMode;
+use config::WriteMode;
 use visitor::FmtVisitor;
 use syntax::codemap::{self, BytePos, Span, Pos};
 use comment::{CodeCharKind, CommentCodeSlices, rewrite_comment};
diff --git a/src/visitor.rs b/src/visitor.rs
index f0efde9de64..1f7de66f91c 100644
--- a/src/visitor.rs
+++ b/src/visitor.rs
@@ -15,9 +15,9 @@ use syntax::visit;
 
 use strings::string_buffer::StringBuffer;
 
-use {Indent, WriteMode};
+use Indent;
 use utils;
-use config::Config;
+use config::{Config, WriteMode};
 use rewrite::{Rewrite, RewriteContext};
 use comment::rewrite_comment;
 use macros::rewrite_macro;
diff --git a/tests/system.rs b/tests/system.rs
index d6f1ba806f5..378998e30a9 100644
--- a/tests/system.rs
+++ b/tests/system.rs
@@ -19,7 +19,8 @@ use std::io::{self, Read, BufRead, BufReader};
 use std::path::Path;
 
 use rustfmt::*;
-use rustfmt::config::{Config, ReportTactic};
+use rustfmt::filemap::write_system_newlines;
+use rustfmt::config::{Config, ReportTactic, WriteMode};
 use rustfmt::rustfmt_diff::*;
 
 static DIFF_CONTEXT_SIZE: usize = 3;
@@ -43,7 +44,7 @@ fn system_tests() {
     // Turn a DirEntry into a String that represents the relative path to the
     // file.
     let files = files.map(get_path_string);
-    let (_reports, count, fails) = check_files(files, WriteMode::Return);
+    let (_reports, count, fails) = check_files(files, WriteMode::Default);
 
     // Display results.
     println!("Ran {} system tests.", count);
@@ -71,7 +72,7 @@ fn idempotence_tests() {
                     .ok()
                     .expect("Couldn't read target dir.")
                     .map(get_path_string);
-    let (_reports, count, fails) = check_files(files, WriteMode::Return);
+    let (_reports, count, fails) = check_files(files, WriteMode::Default);
 
     // Display results.
     println!("Ran {} idempotent tests.", count);
@@ -90,7 +91,7 @@ fn self_tests() {
     // Hack because there's no `IntoIterator` impl for `[T; N]`.
     let files = files.chain(Some("src/lib.rs".to_owned()).into_iter());
 
-    let (reports, count, fails) = check_files(files, WriteMode::Return);
+    let (reports, count, fails) = check_files(files, WriteMode::Default);
     let mut warnings = 0;
 
     // Display results.
@@ -162,8 +163,16 @@ pub fn idempotent_check(filename: String,
     let mut file_map = format(Path::new(&filename), &config, write_mode);
     let format_report = fmt_lines(&mut file_map, &config);
 
-    // Won't panic, as we're not doing any IO.
-    let write_result = filemap::write_all_files(&file_map, WriteMode::Return, &config).unwrap();
+    let mut write_result = HashMap::new();
+    for (filename, text) in file_map.iter() {
+        let mut v = Vec::new();
+        // Won't panic, as we're not doing any IO.
+        write_system_newlines(&mut v, text, &config).unwrap();
+        // Won't panic, we are writing correct utf8.
+        let one_result = String::from_utf8(v).unwrap();
+        write_result.insert(filename.clone(), one_result);
+    }
+
     let target = sig_comments.get("target").map(|x| &(*x)[..]);
 
     handle_result(write_result, target, write_mode).map(|_| format_report)