pw_cli: Add argument to hide banner

This change adds an argument to the pw command which prevents it from
printing the Pigweed banner. This is useful when pw is called from
scripts to avoid polluting the output.

Bug: 143

Change-Id: I30af43bd7815aa0472a1cb1ac2ca3f5ef49976dc

1 files changed, 18 insertions, 4 deletions

diff --git a/pw_cli/py/pw_cli/__main__.py b/pw_cli/py/pw_cli/__main__.py
index ffa5cfdba..e95c7d8ff 100644
--- a/pw_cli/py/pw_cli/__main__.py
+++ b/pw_cli/py/pw_cli/__main__.py
@@ -40,6 +40,13 @@ _PIGWEED_BANNER = '''
 '''
 
 
+class ArgumentParser(argparse.ArgumentParser):
+    def error(self, message: str) -> None:
+        print(colors().magenta(_PIGWEED_BANNER), file=sys.stderr)
+        self.print_usage(sys.stderr)
+        self.exit(2, '%s: error: %s\n' % (self.prog, message))
+
+
 def main(raw_args=None):
     """Entry point for pw command."""
 
@@ -49,15 +56,15 @@ def main(raw_args=None):
     # TODO(keir): Add support for configurable logging levels.
     pw_cli.log.install()
 
-    # Start with the most critical part of the Pigweed command line tool.
-    print(colors().magenta(_PIGWEED_BANNER))
-
     # Add commands and their parsers.
-    parser = argparse.ArgumentParser(
+    parser = ArgumentParser(
         description=__doc__,
         formatter_class=argparse.RawDescriptionHelpFormatter)
 
     parser.add_argument('--loglevel', default='INFO')
+    parser.add_argument('--no-banner',
+                        action='store_true',
+                        help="Don't print the Pigweed banner")
 
     # Default command is 'help'
     pw_cli.plugins.register(
@@ -96,6 +103,10 @@ def main(raw_args=None):
 
     args = parser.parse_args(raw_args)
 
+    # Start with the most critical part of the Pigweed command line tool.
+    if not args.no_banner:
+        print(colors().magenta(_PIGWEED_BANNER))
+
     args_as_dict = dict(vars(args))
     del args_as_dict['_command']
     del args_as_dict['_run_async']
@@ -106,6 +117,9 @@ def main(raw_args=None):
                                      args_as_dict['loglevel'].upper()))
         del args_as_dict['loglevel']
 
+    if 'no_banner' in args_as_dict:
+        del args_as_dict['no_banner']
+
     # Run the command and exit with the appropriate status.
     # pylint: disable=protected-access
     if args._run_async: