Add option to sort keys on dump

Squashed commit of the following: commit e3b379d Author: Robert (Jamie) Munro <rjmunro@arjam.net> Date: Fri May 8 16:10:54 2015 +0100 Add some tests commit febe465 Author: Robert (Jamie) Munro <rjmunro@arjam.net> Date: Fri May 8 15:35:14 2015 +0100 Document options.sortKeys for dumper commit 70e7e3d Author: Robert (Jamie) Munro <rjmunro@arjam.net> Date: Fri May 8 15:33:20 2015 +0100 Allow sortKeys option in dumper Can be `false` (no sorting), `true` (default sorting), or a function (passed to `array.sort(function)` to allow custom ordering commit dee34b1 Author: Robert (Jamie) Munro <rjmunro@arjam.net> Date: Fri May 8 09:43:03 2015 +0100 Sort keys so that the output is deterministic
apibrain · May 13, 2015 · ce0161c · ce0161c
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -1,3 +1,9 @@
+Unreleased
+----------
+
+- Allow options.sortKeys to specify that keys should be sorted when dumping, to
+enable deterministic output.
+
 3.3.0 / 2015-04-26
 ------------------
 

diff --git a/README.md b/README.md
@@ -175,6 +175,8 @@ options:
   block to flow style for collections. -1 means block style everwhere
 - `styles` - "tag" => "style" map. Each tag may have own set of styles.
 - `schema` _(default: `DEFAULT_SAFE_SCHEMA`)_ specifies a schema to use.
+- `sortKeys` _(default: `false`)_ - if `true`, sort keys when dumping YAML. If a
+  function, use the function to sort the keys.
 
 styles:
 

diff --git a/lib/js-yaml/dumper.js b/lib/js-yaml/dumper.js
@@ -114,6 +114,7 @@ function State(options) {
   this.skipInvalid = options['skipInvalid'] || false;
   this.flowLevel   = (common.isNothing(options['flowLevel']) ? -1 : options['flowLevel']);
   this.styleMap    = compileStyleMap(this.schema, options['styles'] || null);
+  this.sortKeys    = options['sortKeys'] || false;
 
   this.implicitTypes = this.schema.compiledImplicit;
   this.explicitTypes = this.schema.compiledExplicit;
@@ -599,6 +600,18 @@ function writeBlockMapping(state, level, object, compact) {
       explicitPair,
       pairBuffer;
 
+  // Allow sorting keys so that the output file is deterministic
+  if (state.sortKeys === true) {
+    // Default sorting
+    objectKeyList.sort();
+  } else if (typeof state.sortKeys === 'function') {
+    // Custom sort function
+    objectKeyList.sort(state.sortKeys);
+  } else if (state.sortKeys) {
+    // Something is wrong
+    throw new YAMLException('sortKeys must be a boolean or a function');
+  }
+
   for (index = 0, length = objectKeyList.length; index < length; index += 1) {
     pairBuffer = '';
 

diff --git a/test/units/sort-keys.js b/test/units/sort-keys.js
@@ -0,0 +1,26 @@
+'use strict';
+
+
+var assert = require('assert');
+var yaml   = require('../../');
+
+var sample = { b: 1, a: 2, c: 3 };
+var unsortedExpected = 'b: 1\na: 2\nc: 3\n';
+var simpleExpected = 'a: 2\nb: 1\nc: 3\n';
+var reverseExpected = 'c: 3\nb: 1\na: 2\n';
+
+test('Dumper should sort preserve key insertion order', function () {
+  assert.deepEqual(yaml.safeDump(sample, { sortKeys: false }), unsortedExpected);
+});
+
+test('Dumper should sort keys when sortKeys is true', function () {
+  assert.deepEqual(yaml.safeDump(sample, { sortKeys: true }), simpleExpected);
+});
+
+test('Dumper should sort keys by sortKeys function when specified', function () {
+  assert.deepEqual(yaml.safeDump(sample, {
+    sortKeys: function (a, b) {
+      return a < b ? 1 : a > b ? -1 : 0;
+    }
+  }), reverseExpected);
+});