1.0.0

README.md

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+# promisify-simple-callback
+
+Promisifies a function that expects a callback with a single (result) argument - in other words, a callback that looks like `function(result) { ... }` - in what should be a reasonably performant manner.
+
+Because sometimes, a module just doesn't conform to the Node.js callback convention.
+
+## License
+
+[WTFPL](http://www.wtfpl.net/txt/copying/) or [CC0](https://creativecommons.org/publicdomain/zero/1.0/), whichever you prefer. A donation and/or attribution are appreciated, but not required.
+
+## Donate
+
+My income consists largely of donations for my projects. If this module is useful to you, consider [making a donation](http://cryto.net/~joepie91/donate.html)!
+
+You can donate using Bitcoin, PayPal, Flattr, cash-in-mail, SEPA transfers, and pretty much anything else.
+
+## Contributing
+
+Pull requests welcome. Please make sure your modifications are in line with the overall code style, and ensure that you're editing the files in `src/`, not those in `lib/`.
+
+Build tool of choice is `gulp`; simply run `gulp` while developing, and it will watch for changes.
+
+Be aware that by making a pull request, you agree to release your modifications under the licenses stated above.
+
+## Usage
+
+```javascript
+var Promise = require("bluebird");
+var promisifySimpleCallback = require("promisify-simple-callback");
+
+/* Pretend that brokenAsyncMethod comes from a third-party library. */
+function brokenAsyncMethod(someArg, options, cb) {
+	doSomething(options, function(err, result) {
+		cb(result);
+	})
+}
+
+/* Promisify it! */
+var promisifiedAsyncMethod = promisifySimpleCallback(brokenAsyncMethod, [null, {}]);
+
+/* Now we can use it normally. */
+Promise.try(function() {
+	return promisifiedAsyncMethod("foobar");
+}).then(function(result) {
+	console.log("Done!", result);
+});
+```
+
+## API
+
+### promisifySimpleCallback(func, [defaults])
+
+Promisifies the given `func`. The promisified method will also catch any synchronous errors, and propagate them as rejections.
+
+You can also specify default argument values; often, there are optional arguments that come before the callback, and by specifying default values, you can make these arguments *really* optional.
+
+Because promisification works by appending a callback at the end of the arguments list, you would otherwise have to include all the optional arguments just to make sure the callback ends up in the right place.
+
+* __func__: The callback-expecting function to promisify.
+* __defaults__: *Optional.* An array of default arguments to fill in. Any argument for which you specify `null` will be skipped - that is, it will be left exactly as is. This means that, for an unspecified argument, it is left to `undefined`.

gulpfile.js

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+var gulp = require('gulp');
+
+var gutil = require('gulp-util');
+var babel = require('gulp-babel');
+var cache = require('gulp-cached');
+var remember = require('gulp-remember');
+var plumber = require('gulp-plumber');
+
+var source = ["src/**/*.js"]
+
+gulp.task('babel', function() {
+	return gulp.src(source)
+		.pipe(plumber())
+		.pipe(cache("babel"))
+		.pipe(babel({presets: ["es2015"]}).on('error', gutil.log)).on('data', gutil.log)
+		.pipe(remember("babel"))
+		.pipe(gulp.dest("lib/"));
+});
+
+gulp.task('watch', function () {
+	gulp.watch(source, ['babel']);
+});
+
+gulp.task('default', ['babel', 'watch']);

index.js

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+'use strict';
+
+module.exports = require("./lib");

lib/index.js

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+'use strict';
+
+var Promise = require("bluebird");
+
+module.exports = function (method) {
+	var defaults = arguments.length <= 1 || arguments[1] === undefined ? [] : arguments[1];
+
+	return function () {
+		var _arguments = arguments,
+		    _this = this;
+
+		return new Promise(function (resolve, reject) {
+			var args = new Array(Math.max(_arguments.length, defaults.length) + 1);
+
+			for (var i = 0; i < args.length; ++i) {
+				args[i] = _arguments[i];
+			}
+
+			if (_arguments.length - 1 < defaults.length) {
+				for (var i = _arguments.length - 1; i < defaults.length; i++) {
+					if (defaults[i] != null) {
+						args[i] = defaults[i];
+					}
+				}
+			}
+
+			args[args.length - 1] = function (result) {
+				resolve(result);
+			};
+
+			console.log(args);
+
+			// Synchronous errors are caught and propagated by Bluebird's `new Promise` already.
+			method.apply(_this, args);
+		});
+	};
+};

package.json

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+{
+  "name": "promisify-simple-callback",
+  "version": "1.0.0",
+  "description": "Promisifies a function that expects a callback with a single (result) argument",
+  "main": "index.js",
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "repository": {
+    "type": "git",
+    "url": "git://github.com/joepie91/node-promisify-simple-callback"
+  },
+  "keywords": [
+    "promisify",
+    "bluebird",
+    "promise"
+  ],
+  "author": "Sven Slootweg",
+  "license": "WTFPL",
+  "dependencies": {
+    "bluebird": "^3.3.3"
+  },
+  "devDependencies": {
+    "babel-preset-es2015": "^6.6.0",
+    "gulp": "^3.9.1",
+    "gulp-babel": "^6.1.2",
+    "gulp-cached": "^1.1.0",
+    "gulp-plumber": "^1.1.0",
+    "gulp-remember": "^0.3.0",
+    "gulp-util": "^3.0.7"
+  }
+}

src/index.js

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+'use strict';
+
+const Promise = require("bluebird");
+
+module.exports = function(method, defaults = []) {
+	return function() {
+		return new Promise((resolve, reject) => {
+			var args = new Array(Math.max(arguments.length, defaults.length) + 1);
+			
+			for(var i = 0; i < args.length; ++i) {
+				args[i] = arguments[i];
+			}
+			
+			if (arguments.length - 1 < defaults.length) {
+				for(var i = arguments.length - 1; i < defaults.length; i++) {
+					if (defaults[i] != null) {
+						args[i] = defaults[i];
+					}
+				}
+			}
+			
+			args[args.length - 1] = function(result) {
+				resolve(result);
+			}
+			
+			console.log(args);
+			
+			// Synchronous errors are caught and propagated by Bluebird's `new Promise` already.
+			method.apply(this, args);
+		})
+	}
+	
+}