Refactored clipboard code to make it a tiny bit simpler

Also added a few unit tests related to running an empty statement and dealing with precmd hook success and failure.

Author: tleonhardt

cmd2.py

@@ -303,27 +303,25 @@ def new_func(instance, arg):
     return option_setup
 
 
-# Can we access the clipboard, always true on Windows and Mac, but only sometimes on Linux
-can_clip = True
-if sys.platform.startswith('linux'):
-    try:
-        pyperclip.paste()
-    except pyperclip.exceptions.PyperclipException:
-        can_clip = False
+# Can we access the clipboard?  Should always be true on Windows and Mac, but only sometimes on Linux
+try:
+    pyperclip.paste()
+except pyperclip.exceptions.PyperclipException:
+    can_clip = False
+else:
+    can_clip = True
 
 
 def get_paste_buffer():
     """Get the contents of the clipboard / paste buffer.
 
     :return: str - contents of the clipboard
     """
-    pb_unicode = pyperclip.paste()
+    pb_str = pyperclip.paste()
 
-    if six.PY3:
-        pb_str = pb_unicode
-    else:
+    if six.PY2:
         import unicodedata
-        pb_str = unicodedata.normalize('NFKD', pb_unicode).encode('ascii', 'ignore')
+        pb_str = unicodedata.normalize('NFKD', pb_str).encode('ascii', 'ignore')
 
     return pb_str
 
@@ -368,16 +366,15 @@ def replace_with_file_contents(fname):
     """Action to perform when successfully matching parse element definition for inputFrom parser.
 
     :param fname: str - filename
-    :return: str - contents of file "fname" or contents of the clipboard if fname is None or an empty string
+    :return: str - contents of file "fname"
     """
-    if fname:
-        try:
-            with open(os.path.expanduser(fname[0])) as source_file:
-                result = source_file.read()
-        except IOError:
-            result = '< %s' % fname[0]  # wasn't a file after all
-    else:
-        result = get_paste_buffer()
+    try:
+        with open(os.path.expanduser(fname[0])) as source_file:
+            result = source_file.read()
+    except IOError:
+        result = '< %s' % fname[0]  # wasn't a file after all
+
+    # TODO: IF pyparsing input parser logic gets fixed to support empty file, add support to get from paste buffer
     return result
 
 

tests/test_cmd2.py

@@ -25,6 +25,11 @@ def test_ver():
     assert cmd2.__version__ == '0.7.4'
 
 
+def test_empty_statement(base_app):
+    out = run_cmd(base_app, '')
+    expected = normalize('')
+    assert out == expected
+
 def test_base_help(base_app):
     out = run_cmd(base_app, 'help')
     expected = normalize(BASE_HELP)
@@ -683,3 +688,29 @@ def test_cmdloop_without_rawinput():
         app.cmdloop()
     out = app.stdout.buffer
     assert out == expected
+
+
+class HookFailureApp(cmd2.Cmd):
+    def __init__(self, *args, **kwargs):
+        # Need to use this older form of invoking super class constructor to support Python 2.x and Python 3.x
+        cmd2.Cmd.__init__(self, *args, **kwargs)
+
+    def postparsing_precmd(self, statement):
+        """Simulate precmd hook failure."""
+        return True, statement
+
+
+@pytest.fixture
+def hook_failure():
+    app = HookFailureApp()
+    app.stdout = StdOut()
+    return app
+
+def test_precmd_hook_success(base_app):
+    out = base_app.onecmd_plus_hooks('help')
+    assert out is None
+
+
+def test_precmd_hook_failure(hook_failure):
+    out = hook_failure.onecmd_plus_hooks('help')
+    assert out == True