From 0d08e73f0a5a3ef110f00bb57bca8f40e962c697 Mon Sep 17 00:00:00 2001
From: Blaine Bublitz <blaine.bublitz@gmail.com>
Date: Sun, 27 Sep 2015 14:38:55 -0700
Subject: [PATCH] allow a function to be used as value for the overwrite option
 - closes #68

---
 lib/prepareWrite.js | 11 ++++++-
 test/dest.js        | 70 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 80 insertions(+), 1 deletion(-)

diff --git a/lib/prepareWrite.js b/lib/prepareWrite.js
index 9779c701..621d9b54 100644
--- a/lib/prepareWrite.js
+++ b/lib/prepareWrite.js
@@ -5,6 +5,14 @@ var path = require('path');
 var mkdirp = require('mkdirp');
 var fs = require('graceful-fs');
 
+function booleanOrFunc(v, file) {
+  if (typeof v !== 'boolean' && typeof v !== 'function') {
+    return null;
+  }
+
+  return typeof v === 'boolean' ? v : v(file);
+}
+
 function stringOrFunc(v, file) {
   if (typeof v !== 'string' && typeof v !== 'function') {
     return null;
@@ -20,7 +28,8 @@ function prepareWrite(outFolder, file, opt, cb) {
     dirMode: null,
     overwrite: true
   }, opt);
-  options.flag = (options.overwrite ? 'w' : 'wx');
+  var overwrite = booleanOrFunc(options.overwrite, file);
+  options.flag = (overwrite ? 'w' : 'wx');
 
   var cwd = path.resolve(options.cwd);
   var outFolderPath = stringOrFunc(outFolder, file);
diff --git a/test/dest.js b/test/dest.js
index 7b41146c..edd4e3d0 100644
--- a/test/dest.js
+++ b/test/dest.js
@@ -903,6 +903,76 @@ describe('dest stream', function() {
     stream.end();
   });
 
+  it('should not overwrite files with overwrite option set to a function that returns false', function(done) {
+    var inputPath = path.join(__dirname, './fixtures/test.coffee');
+    var inputBase = path.join(__dirname, './fixtures/');
+    var inputContents = fs.readFileSync(inputPath);
+
+    var expectedPath = path.join(__dirname, './out-fixtures/test.coffee');
+    var expectedBase = path.join(__dirname, './out-fixtures');
+    var existingContents = 'Lorem Ipsum';
+
+    var inputFile = new File({
+      base: inputBase,
+      cwd: __dirname,
+      path: inputPath,
+      contents: inputContents
+    });
+
+    var onEnd = function(){
+      buffered.length.should.equal(1);
+      bufEqual(fs.readFileSync(expectedPath), new Buffer(existingContents)).should.equal(true);
+      done();
+    };
+
+    // Write expected file which should not be overwritten
+    fs.mkdirSync(expectedBase);
+    fs.writeFileSync(expectedPath, existingContents);
+
+    var stream = vfs.dest('./out-fixtures/', {cwd: __dirname, overwrite: function() { return false; }});
+
+    var buffered = [];
+    bufferStream = through.obj(dataWrap(buffered.push.bind(buffered)), onEnd);
+    stream.pipe(bufferStream);
+    stream.write(inputFile);
+    stream.end();
+  });
+
+  it('should overwrite files with overwrite option set to a function that returns true', function(done) {
+    var inputPath = path.join(__dirname, './fixtures/test.coffee');
+    var inputBase = path.join(__dirname, './fixtures/');
+    var inputContents = fs.readFileSync(inputPath);
+
+    var expectedPath = path.join(__dirname, './out-fixtures/test.coffee');
+    var expectedBase = path.join(__dirname, './out-fixtures');
+    var existingContents = 'Lorem Ipsum';
+
+    var inputFile = new File({
+      base: inputBase,
+      cwd: __dirname,
+      path: inputPath,
+      contents: inputContents
+    });
+
+    var onEnd = function(){
+      buffered.length.should.equal(1);
+      bufEqual(fs.readFileSync(expectedPath), new Buffer(inputContents)).should.equal(true);
+      done();
+    };
+
+    // This should be overwritten
+    fs.mkdirSync(expectedBase);
+    fs.writeFileSync(expectedPath, existingContents);
+
+    var stream = vfs.dest('./out-fixtures/', {cwd: __dirname, overwrite: function() { return true; }});
+
+    var buffered = [];
+    bufferStream = through.obj(dataWrap(buffered.push.bind(buffered)), onEnd);
+    stream.pipe(bufferStream);
+    stream.write(inputFile);
+    stream.end();
+  });
+
   it('should create symlinks when the `symlink` attribute is set on the file', function (done) {
     var inputPath = path.join(__dirname, './fixtures/test-create-dir-symlink');
     var inputBase = path.join(__dirname, './fixtures/');