Get argparser to return help string instead of printing (#30)

* NonPrintingParser raises PrintingException instead of printing

* Switch to using NonPrintingParser instead of ArgumentParser

* Test that help/error messages return strings instead of printing

* Check for raising PrintingException instead of SystemExit

* Python 2/3 compatibility for strings

hca/__init__.py

@@ -14,5 +14,7 @@ def main():
     response = cli.make_request(sys.argv[1:])
     if isinstance(response, requests.Response):
         print(response.content.decode())
+    elif type(response) == str:
+        print(response)
     else:
         print(json.dumps(response))

hca/argument_parser.py

@@ -0,0 +1,13 @@
+import argparse
+
+from .error import PrintingException
+
+
+class NonPrintingParser(argparse.ArgumentParser):
+    """ArgumentParser that will return help and error strings instead of printing."""
+
+    def print_usage(self, file=None):
+        raise PrintingException(self.format_usage())
+
+    def print_help(self, file=None):
+        raise PrintingException(self.format_help())

hca/cli.py

@@ -1,20 +1,21 @@
 from __future__ import absolute_import, division, print_function, unicode_literals
 
-import argparse
 import inspect
 import pkgutil
 import sys
 
 from .added_command import AddedCommand
 from .api import autogenerated, composite_commands
+from .argument_parser import NonPrintingParser
+from .error import PrintingException
 
 
 class CLI:
     """Class for interacting with users through a CLI."""
 
     def __init__(self, test_api_path=None):
         """Initialize the CLI API."""
-        self.parser = argparse.ArgumentParser()  # Need to add description based on spec.
+        self.parser = NonPrintingParser()  # Need to add description based on spec.
         self.commands = {}
         subparsers = self.parser.add_subparsers(help='sub-command help')
         prefix = autogenerated.__name__ + "."
@@ -46,9 +47,15 @@ def parse_args(self, command_line_input):
     def make_request(self, command_line_input, stream=False):
         """Function to actually make request to api."""
         if not command_line_input:
-            self.parser.print_help()
-            self.parser.exit(1)
-        args = self.parse_args(command_line_input)
+            return self.parser.format_help()
+
+        # Handles PrintingException if Base ArgumentParser was going to print.
+        try:
+            args = self.parse_args(command_line_input)
+        except PrintingException as pe:
+            msg = pe.args[0]
+            return msg
+
         endpoint = command_line_input[0]
 
         command = self.commands.get(endpoint, None)

hca/error.py

@@ -1,3 +1,10 @@
 class APIException(Exception):
     def __init__(self, *args, **kwargs):
         super(APIException, self).__init__(*args, **kwargs)
+
+
+class PrintingException(Exception):
+    """NonPrintingParser will raise this to notify CLI to exit and transfer help message (needed for slackbot)."""
+
+    def __init__(self, *args, **kwargs):
+        super(PrintingException, self).__init__(*args, **kwargs)

test/test.py

@@ -160,6 +160,7 @@ def test_index_parameters(self):
     def test_parsing(self):
         """Test that the parser parses arguments correctly."""
         import hca.cli
+        import hca.error
 
         cli = hca.cli.CLI(os.path.join(os.path.dirname(os.path.realpath(__file__)), "test.json"))
 
@@ -171,13 +172,13 @@ def test_parsing(self):
         self.assertEqual(cli.parse_args(args), out)
 
         args = ["put-files", "--creator-uid", "1", "--source-url", "sljdf.com", "134"]
-        self.assertRaises(SystemExit, cli.parse_args, args)
+        self.assertRaises(hca.error.PrintingException, cli.parse_args, args)
 
         args = ["put-files", "--bundle-uuid", "asdf", "--creator-uid", "1", "--source-url", "sljdf.com"]
-        self.assertRaises(SystemExit, cli.parse_args, args)
+        self.assertRaises(hca.error.PrintingException, cli.parse_args, args)
 
         args = ["put-files", "--bundle-uuid", "--creator-uid", "1", "--source-url", "sljdf.com", "134"]
-        self.assertRaises(SystemExit, cli.parse_args, args)
+        self.assertRaises(hca.error.PrintingException, cli.parse_args, args)
 
         args = ["get-bundles", "uuid_arg"]
         out = {"uuid": "uuid_arg"}
@@ -197,6 +198,31 @@ def test_parsing(self):
         out = {"uuid": "uuid_arg", "replica": "rep"}
         self.assertEqual(cli.parse_args(args), out)
 
+    def test_cli_printing(self):
+        import hca.cli
+        cli = hca.cli.CLI()
+        string = str if six.PY3 else basestring
+
+        # No args given
+        request = cli.make_request([])
+        self.assertIsInstance(request, string)
+
+        # Base parser help
+        request = cli.make_request(["-h"])
+        self.assertIsInstance(request, string)
+
+        # Endpoint parser help
+        request = cli.make_request(["put-bundles", "-h"])
+        self.assertIsInstance(request, string)
+
+        # Base args given incorrectly
+        request = cli.make_request(["idontbelonghere"])
+        self.assertIsInstance(request, string)
+
+        # Endpoint args given incorrectly
+        request = cli.make_request(["put-bundles", "idontbelonghere"])
+        self.assertIsInstance(request, string)
+
     def _get_first_url(self, response):
         """Get the first url we sent a request to if there were redirects."""
         if response.history: