Make iDisplay.menu() calls non-interactive where possible

- And provide helpful errors where they're not

letsencrypt-apache/letsencrypt_apache/display_ops.py

@@ -78,11 +78,17 @@ def _vhost_menu(domain, vhosts):
                 name_size=disp_name_size)
         )
 
+    try:
         code, tag = zope.component.getUtility(interfaces.IDisplay).menu(
             "We were unable to find a vhost with a ServerName or Address of {0}.{1}"
-        "Which virtual host would you like to choose?".format(
+            "Which virtual host would you like to choose?".format(domain, os.linesep),
-            domain, os.linesep),
             choices, help_label="More Info", ok_label="Select")
+    except errors.MissingCommandlineFlag, e:
+        msg = ("Failed to run Apache plugin non-interactively{1}{0}{1}"
+               "(The best solution is to add ServerName or ServerAlias entries to "
+               "the VirtualHost directives of your apache configuration files.)".format(e,
+               os.linesep))
+        raise errors.MissingCommandlineFlag, msg
 
     return code, tag
 

letsencrypt/cli.py

@@ -280,7 +280,7 @@ def _handle_identical_cert_request(config, cert):
                "Cancel this operation and do nothing"]
 
     display = zope.component.getUtility(interfaces.IDisplay)
-    response = display.menu(question, choices, "OK", "Cancel")
+    response = display.menu(question, choices, "OK", "Cancel", default=0)
     if response[0] == "cancel" or response[1] == 2:
         # TODO: Add notification related to command-line options for
         #       skipping the menu for this case.

letsencrypt/display/enhancements.py

@@ -48,7 +48,7 @@ def redirect_by_default():
 
     code, selection = util(interfaces.IDisplay).menu(
         "Please choose whether HTTPS access is required or optional.",
-        choices)
+        choices, default=0, cli_flag="--redirect / --no-redirect")
 
     if code != display_util.OK:
         return False

letsencrypt/display/ops.py

@@ -31,8 +31,16 @@ def choose_plugin(prepared, question):
             for plugin_ep in prepared]
 
     while True:
-        code, index = util(interfaces.IDisplay).menu(
+        disp = util(interfaces.IDisplay)
-            question, opts, help_label="More Info")
+        try:
+            code, index = disp.menu(question, opts, help_label="More Info")
+        except errors.MissingCommandlineFlag:
+            # use a custom message for this case
+            raise errors.MissingCommandlineFlag, ("Missing command line flags. For non-interactive "
+                "execution, you will need to specify a plugin on the command line.  Run with "
+                "'--help plugins' to see a list of options, and see "
+                " https://eff.org/letsencrypt-plugins for more detail on what the plugins "
+                "do and how to use them.")
 
         if code == display_util.OK:
             plugin_ep = prepared[index]