Merge djmitche/build-relengapi:repl-subcommand (PR #217)

docs/development/@relengapi/databases.rst

@@ -131,6 +131,27 @@ The list of database names is at ``current_app.db.database_names``.
 
 The known metadata for each database is in ``current_app.db.metadata``, keyed by database name.
 
+Interactive Use
+---------------
+
+It can sometimes be useful to "live" ORM operations at an interactive prompt.
+The ``relengapi repl`` command will run a read-eval-print loop with an active RelengAPI app:
+
+.. code-block:: none
+
+    $ relengapi repl
+    2015-04-08 15:20:16,642 registering blueprint badpenny
+    2015-04-08 15:20:16,644 registering blueprint base
+    2015-04-08 15:20:16,645 registering blueprint tokenauth
+    2015-04-08 15:20:16,646 registering blueprint auth
+    2015-04-08 15:20:16,647 registering blueprint docs
+    'app' is the current application.
+    Python 2.7.9 (default, Feb 22 2015, 12:26:28)
+    [GCC 4.8.3] on linux2
+    Type "help", "copyright", "credits" or "license" for more information.
+    (InteractiveConsole)
+    >>> s = app.db.session('relengapi')
+
 Alternative Column types
 ------------------------
 

relengapi/blueprints/base/__init__.py

@@ -85,3 +85,25 @@ def make_parser(self, subparsers):
 
     def run(self, parser, args):
         current_app.aws._spawn_sqs_listeners()
+
+
+class ReplSubcommand(subcommands.Subcommand):
+
+    def make_parser(self, subparsers):
+        parser = subparsers.add_parser(
+            'repl', help='Open a Python REPL in the RelengAPI application context; '
+                         '`app` is the current app.')
+        return parser
+
+    def run(self, parser, args):
+        import code
+        # try to get readline for the interactive interpreter (it
+        # only uses it if it's already loaded)
+        try:
+            import readline
+            assert readline
+        except ImportError:
+            readline = None
+
+        print "'app' is the current application."
+        code.InteractiveConsole(locals={'app': current_app}).interact()