From 7df465e3d95b901493fb146cf92586138da496c6 Mon Sep 17 00:00:00 2001
From: Lars Wirzenius <liw@liw.fi>
Date: Sun, 30 Apr 2017 11:16:02 +0300
Subject: Add Variables.append()

---
 fail-tests/fail.stdout-diff |  2 +-
 yarnutils/vars.py           |  9 +++++++++
 yarnutils/vars_tests.py     | 18 ++++++++++++++++++
 3 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/fail-tests/fail.stdout-diff b/fail-tests/fail.stdout-diff
index 4f43f5c..47ac588 100644
--- a/fail-tests/fail.stdout-diff
+++ b/fail-tests/fail.stdout-diff
@@ -1,4 +1,4 @@
 --- /dev/null	2017-04-20 17:06:09.455944599 +0300
-+++ fail-tests/fail.stdout-actual	2017-04-30 11:10:57.309026170 +0300
++++ fail-tests/fail.stdout-actual	2017-04-30 11:15:56.619905930 +0300
 @@ -0,0 +1 @@
 +this is not empty output to make test fail
diff --git a/yarnutils/vars.py b/yarnutils/vars.py
index 9349a2d..b221ba6 100644
--- a/yarnutils/vars.py
+++ b/yarnutils/vars.py
@@ -51,3 +51,12 @@ class Variables(object):
 
     def save(self):
         self._save(self._dict)
+
+    def append(self, key, value):
+        if key in self._dict:
+            if not isinstance(self[key], list):
+                raise Exception('Value for {} is not a list'.format(key))
+        if key not in self._dict:
+            self._dict[key] = []
+        self._dict[key].append(value)
+        self.save()
diff --git a/yarnutils/vars_tests.py b/yarnutils/vars_tests.py
index 821d2a5..b42a1eb 100644
--- a/yarnutils/vars_tests.py
+++ b/yarnutils/vars_tests.py
@@ -60,3 +60,21 @@ class VariablesTests(unittest.TestCase):
         vars2 = yarnutils.Variables(self.tempdir)
         self.assertEqual(vars1['foo'], vars2['foo'])
         self.assertEqual(vars2['foo'], [0])
+
+    def test_appends_to_unset_key(self):
+        vars = yarnutils.Variables(self.tempdir)
+        vars.append('foo', 0)
+        self.assertEqual(vars['foo'], [0])
+
+    def test_append_saves(self):
+        vars1 = yarnutils.Variables(self.tempdir)
+        vars1.append('foo', 0)
+        vars2 = yarnutils.Variables(self.tempdir)
+        self.assertEqual(vars1['foo'], vars2['foo'])
+        self.assertEqual(vars2['foo'], [0])
+
+    def test_append_gives_error_if_appending_to_nonlist_value(self):
+        vars = yarnutils.Variables(self.tempdir)
+        vars['foo'] = 0
+        with self.assertRaises(Exception):
+            vars.append('foo', 0)
-- 
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