Maintain windows line ending (#472)

It's nice that we print line endings in a single place, it was super easy to preserve them :)

Fixes #92

index.js

@@ -8,6 +8,14 @@ const normalizeOptions = require("./src/options").normalize;
 const parser = require("./src/parser");
 const printDocToDebug = require("./src/doc-debug").printDocToDebug;
 
+function guessLineEnding(text) {
+  const index = text.indexOf("\n");
+  if (index >= 0 && text.charAt(index - 1) === "\r") {
+    return "\r\n";
+  }
+  return "\n";
+}
+
 function parse(text, opts) {
   const parseFunction = opts.parser === "flow"
     ? parser.parseWithFlow
@@ -42,7 +50,7 @@ function format(text, opts) {
   const ast = parse(text, opts);
   attachComments(text, ast, opts);
   const doc = printAstToDoc(ast, opts);
-  const str = printDocToString(doc, opts.printWidth);
+  const str = printDocToString(doc, opts.printWidth, guessLineEnding(text));
   return str;
 }
 
@@ -55,9 +63,9 @@ function formatWithShebang(text, opts) {
   const shebang = text.slice(0, index + 1);
   const programText = text.slice(index + 1);
   const nextChar = text.charAt(index + 1);
-  const addNewline = nextChar == "\n" || nextChar == "\r";
+  const newLine = nextChar === "\n" ? "\n" : (nextChar === "\r" ? "\r\n" : "");
 
-  return shebang + (addNewline ? "\n" : "") + format(programText, opts);
+  return shebang + newLine + format(programText, opts);
 }
 
 module.exports = {

src/doc-printer.js

@@ -76,7 +76,9 @@ function fits(next, restCommands, width) {
   return false;
 }
 
-function printDocToString(doc, w) {
+function printDocToString(doc, width, newLine) {
+  newLine = newLine || "\n";
+
   let pos = 0;
   // cmds is basically a stack. We've turned a recursive call into a
   // while loop which is much faster. The while loop below adds new
@@ -126,7 +128,7 @@ function printDocToString(doc, w) {
               shouldRemeasure = false;
 
               const next = [ ind, MODE_FLAT, doc.contents ];
-              let rem = w - pos;
+              let rem = width - pos;
 
               if (!doc.break && fits(next, cmds, rem)) {
                 cmds.push(next);
@@ -212,7 +214,7 @@ function printDocToString(doc, w) {
 
             case MODE_BREAK:
               if (doc.literal) {
-                out.push(lineSuffix + "\n");
+                out.push(lineSuffix + newLine);
                 pos = 0;
               } else {
                 if (out.length > 0) {
@@ -223,7 +225,7 @@ function printDocToString(doc, w) {
                   );
                 }
 
-                out.push(lineSuffix + "\n" + " ".repeat(ind));
+                out.push(lineSuffix + newLine + " ".repeat(ind));
                 pos = ind;
               }
 

tests/windows/__snapshots__/jsfmt.spec.js.snap

@@ -0,0 +1,14 @@
+exports[`test line-ending.js 1`] = `
+"this;
+has;
+windows;
+line;
+endings;
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+this;
+has;
+windows;
+line;
+endings;
+"
+`;

tests/windows/jsfmt.spec.js

@@ -0,0 +1 @@
+run_spec(__dirname);

tests/windows/line-ending.js

@@ -0,0 +1,5 @@
+this;
+has;
+windows;
+line;
+endings;