Add FromGNArgs() to gn_helpers.

build/gn_helpers_unittest.py

Index: build/gn_helpers_unittest.py
diff --git a/build/gn_helpers_unittest.py b/build/gn_helpers_unittest.py
index 72123f9359cd438089ae6d52f3be86fbbbded454..cc6018a17210ab86d07b321c8490180d8803a04c 100644
--- a/build/gn_helpers_unittest.py
+++ b/build/gn_helpers_unittest.py
@@ -76,5 +76,42 @@ class UnitTest(unittest.TestCase):
       parser = gn_helpers.GNValueParser('[1 2]')  # No separating comma.
       parser.ParseList()
 
+  def test_FromGNArgs(self):
+    # Booleans and numbers should work; whitespace is allowed works.
+    self.assertEqual(gn_helpers.FromGNArgs('foo = true\nbar = 1\n'),
+                     {'foo': True, 'bar': 1})
+
+    # Whitespace is not required; strings should also work.
+    self.assertEqual(gn_helpers.FromGNArgs('foo="bar baz"'),
+                     {'foo': 'bar baz'})
+
+    # Lists should work.
+    self.assertEqual(gn_helpers.FromGNArgs('foo=[1, 2, 3]'),
+                     {'foo': [1, 2, 3]})
+
+    # Empty strings should return an empty dict.
+    self.assertEqual(gn_helpers.FromGNArgs(''), {})
+    self.assertEqual(gn_helpers.FromGNArgs(' \n '), {})
+
+    # Non-identifiers should raise an exception.
+    with self.assertRaises(gn_helpers.GNException):
+      gn_helpers.FromGNArgs('123 = true')
+
+    # References to other variables should raise an exception.
+    with self.assertRaises(gn_helpers.GNException):
+      gn_helpers.FromGNArgs('foo = bar')
+
+    # References to functions should raise an exception.
+    with self.assertRaises(gn_helpers.GNException):
+      gn_helpers.FromGNArgs('foo = exec_script("//build/baz.py")')
+
+    # Underscores in identifiers should work.
+    self.assertEqual(gn_helpers.FromGNArgs('_foo = true'),
+                     {'_foo': True})
+    self.assertEqual(gn_helpers.FromGNArgs('foo_bar = true'),
+                     {'foo_bar': True})
+    self.assertEqual(gn_helpers.FromGNArgs('foo_=true'),
+                     {'foo_': True})
+
 if __name__ == '__main__':
   unittest.main()