issue #393: Usage error should show there is a --help option

click/exceptions.py

@@ -44,14 +44,20 @@ class UsageError(ClickException):
     def __init__(self, message, ctx=None):
         ClickException.__init__(self, message)
         self.ctx = ctx
+        self.cmd = self.ctx and self.ctx.command or None
 
     def show(self, file=None):
         if file is None:
             file = get_text_stderr()
         color = None
+        hint = ''
+        if (self.cmd is not None and
+                self.cmd.get_help_option(self.ctx) is not None):
+            hint = ('Try "%s %s" for help.\n'
+                    % (self.ctx.command_path, self.ctx.help_option_names[0]))
         if self.ctx is not None:
             color = self.ctx.color
-            echo(self.ctx.get_usage() + '\n', file=file, color=color)
+            echo(self.ctx.get_usage() + '\n%s' % hint, file=file, color=color)
         echo('Error: %s' % self.format_message(), file=file, color=color)
 
 

docs/quickstart.rst

@@ -79,7 +79,7 @@ And if you want to go back to the real world, use the following command::
 
     $ deactivate
 
-After doing this, the prompt of your shell should be as familar as before.
+After doing this, the prompt of your shell should be as familiar as before.
 
 Now, let's move on. Enter the following command to get Click activated in your
 virtualenv::

tests/test_formatting.py

@@ -145,3 +145,70 @@ def cli():
         'Options:',
         '  --help  Show this message and exit.',
     ]
+
+
+def test_formatting_usage_error(runner):
+    @click.command()
+    @click.argument('arg')
+    def cmd(arg):
+        click.echo('arg:' + arg)
+
+    result = runner.invoke(cmd, [])
+    assert result.exit_code == 2
+    assert result.output.splitlines() == [
+        'Usage: cmd [OPTIONS] ARG',
+        'Try "cmd --help" for help.',
+        '',
+        'Error: Missing argument "arg".'
+    ]
+
+
+def test_formatting_usage_error_nested(runner):
+    @click.group()
+    def cmd():
+        pass
+
+    @cmd.command()
+    @click.argument('bar')
+    def foo(bar):
+        click.echo('foo:' + bar)
+
+    result = runner.invoke(cmd, ['foo'])
+    assert result.exit_code == 2
+    assert result.output.splitlines() == [
+        'Usage: cmd foo [OPTIONS] BAR',
+        'Try "cmd foo --help" for help.',
+        '',
+        'Error: Missing argument "bar".'
+    ]
+
+
+def test_formatting_usage_error_no_help(runner):
+    @click.command(add_help_option=False)
+    @click.argument('arg')
+    def cmd(arg):
+        click.echo('arg:' + arg)
+
+    result = runner.invoke(cmd, [])
+    assert result.exit_code == 2
+    assert result.output.splitlines() == [
+        'Usage: cmd [OPTIONS] ARG',
+        '',
+        'Error: Missing argument "arg".'
+    ]
+
+
+def test_formatting_usage_custom_help(runner):
+    @click.command(context_settings=dict(help_option_names=['--man']))
+    @click.argument('arg')
+    def cmd(arg):
+        click.echo('arg:' + arg)
+
+    result = runner.invoke(cmd, [])
+    assert result.exit_code == 2
+    assert result.output.splitlines() == [
+        'Usage: cmd [OPTIONS] ARG',
+        'Try "cmd --man" for help.',
+        '',
+        'Error: Missing argument "arg".'
+    ]