support "#{ENV['FOO']}" expressions in knife.rb

Author: dcrosta

chef/api.py

@@ -67,6 +67,7 @@ class ChefAPI(object):
     """
 
     ruby_value_re = re.compile(r'#\{([^}]+)\}')
+    env_value_re = re.compile(r'ENV\[(.+)\]')
 
     def __init__(self, url, key, client, version='0.10.8', headers={}):
         self.url = url.rstrip('/')
@@ -105,6 +106,10 @@ def _ruby_value(match):
                 expr = match.group(1).strip()
                 if expr == 'current_dir':
                     return os.path.dirname(path)
+                envmatch = cls.env_value_re.match(expr)
+                if envmatch:
+                    envmatch = envmatch.group(1).strip('"').strip("'")
+                    return os.environ.get(envmatch) or ''
                 log.debug('Unknown ruby expression in line "%s"', line)
                 raise UnknownRubyExpression
             try:

chef/tests/test_api.py

@@ -18,3 +18,10 @@ def test_current_dir(self):
         api = self.load('current_dir.rb')
         path = os.path.join(os.path.dirname(__file__), 'configs', 'test_1')
         self.assertEqual(api.client, path)
+
+    def test_env_variables(self):
+        username = os.environ.get('LOGNAME')
+        if username is None:
+            self.fail('could not read $LOGNAME from environment')
+        api = self.load('env_values.rb')
+        self.assertEqual(api.client, username)