Implement --debug flag, fixes #124

docs/changelog.rst

@@ -2,6 +2,8 @@
 Changelog
 =========
 
+* :feature:`124` Add a ``--debug`` flag to the core parser to enable easier
+  debugging (on top of existing ``INVOKE_DEBUG`` env var.)
 * :feature:`125` Improve output of Failure exceptions when printed.
 * :release:`0.7.0 <2014.01.28>`
 * :feature:`109` Add a ``default`` kwarg to `.Collection.add_task` allowing

invoke/cli.py

@@ -9,7 +9,7 @@
 from .parser import Parser, Context as ParserContext, Argument
 from .executor import Executor
 from .exceptions import Failure, CollectionNotFound, ParseError
-from .util import debug, pty_size
+from .util import debug, pty_size, enable_logging
 from ._version import __version__
 
 
@@ -147,6 +147,10 @@ def parse(argv, collection=None):
     debug("After core-args pass, leftover argv: %r" % (core.unparsed,))
     args = core[0].args
 
+    # Enable debugging from here on out, if debug flag was given.
+    if args.debug.value:
+        enable_logging()
+
     # Print version & exit if necessary
     if args.version.value:
         print("Invoke %s" % __version__)

invoke/util.py

@@ -6,10 +6,13 @@
 import termios
 
 
+def enable_logging():
+    logging.basicConfig(level=logging.DEBUG)
+
 # Allow from-the-start debugging (vs toggled during load of tasks module) via
-# shell env var
+# shell env var.
 if os.environ.get('INVOKE_DEBUG'):
-    logging.basicConfig(level=logging.DEBUG)
+    enable_logging()
 
 # Add top level logger functions to global namespace. Meh.
 log = logging.getLogger('invoke')

tests/_support/debugging.py

@@ -0,0 +1,7 @@
+from invoke import task
+from invoke.util import debug
+
+
+@task
+def foo():
+    debug("my-sentinel")

tests/cli.py

@@ -229,10 +229,7 @@ def no_deduping(self):
 
     @trap
     def debug_flag(self):
-        expected = """
-wut
-"""
-        eq_(run("invoke -d -c debugging foo").stdout, expected)
+        assert 'my-sentinel' in run("invoke -d -c debugging foo").stderr
 
     class run_options:
         "run() related CLI flags"