[diffoscope] 01/04: diffoscope: Specify choices for --list-tools switch.

[Mattia Rizzolo]

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mattia pushed a commit to branch master
in repository diffoscope.

commit 3253f1452538469d6b6f4d3f5fc8189b9fbc6a57
Author: Brett Smith <brettcsmith at brettcsmith.org>
Date:   Fri Dec 30 23:18:14 2016 -0500

    diffoscope: Specify choices for --list-tools switch.
    
    This gives the user more information about what they can specify as an
    argument, and generates a nicer error message if they give an unrecognized
    argument.
    
    With that done, we can simplify the implementation of ListToolsAction,
    because argparse has already validated the argument.
    
    Signed-off-by: Mattia Rizzolo <mattia at debian.org>
---
 diffoscope/main.py  | 20 ++++++++------------
 diffoscope/tools.py | 13 ++++++++-----
 2 files changed, 16 insertions(+), 17 deletions(-)

diff --git a/diffoscope/main.py b/diffoscope/main.py
index c374d8d..64e06fa 100644
--- a/diffoscope/main.py
+++ b/diffoscope/main.py
@@ -62,7 +62,11 @@ def create_parser():
     parser.add_argument('--version', action='version',
                         version='diffoscope %s' % VERSION)
     parser.add_argument('--list-tools', nargs='?', type=str, action=ListToolsAction,
-                        help='Show external tools required and exit')
+                        metavar='DISTRO', choices=sorted(OS_NAMES),
+                        help='Show external tools required and exit. '
+                        'DISTRO can be one of {%(choices)s}. '
+                        'If specified, the output will list packages in that '
+                        'distribution that satisfy these dependencies.')
     parser.add_argument('--debug', dest='debug', action='store_true',
                         default=False, help='Display debug messages')
     parser.add_argument('--debugger', action='store_true',
@@ -184,20 +188,12 @@ class ListToolsAction(argparse.Action):
         print("External-Tools-Required: ", end='')
         print(', '.join(sorted(tool_required.all)))
         if os_override:
-            if os_override in OS_NAMES.keys():
-                os_list = [os_override]
-            else:
-                print()
-                print("No package mapping found for: {} (possible values: {})".format(os_override, ", ".join(sorted(OS_NAMES.keys()))), file=sys.stderr)
-                sys.exit(1)
+            os_list = [os_override]
         else:
             current_os = get_current_os()
-            if current_os in OS_NAMES.keys():
-                os_list = [current_os]
-            else:
-                os_list = OS_NAMES.keys()
+            os_list = [current_os] if (current_os in OS_NAMES) else iter(OS_NAMES)
         for os in os_list:
-            print("Available-in-{}-packages: ".format(OS_NAMES.get(os, os)), end='')
+            print("Available-in-{}-packages: ".format(OS_NAMES[os]), end='')
             print(', '.join(sorted(filter(None, {
                 EXTERNAL_TOOLS.get(k, {}).get(os, None)
                 for k in tool_required.all
diff --git a/diffoscope/tools.py b/diffoscope/tools.py
index 8393284..8af5aa3 100644
--- a/diffoscope/tools.py
+++ b/diffoscope/tools.py
@@ -17,6 +17,7 @@
 # You should have received a copy of the GNU General Public License
 # along with diffoscope.  If not, see <https://www.gnu.org/licenses/>.
 
+import collections
 import platform
 import functools
 
@@ -28,11 +29,13 @@ from .profiling import profile
 # calls
 find_executable = functools.lru_cache()(find_executable)
 
-OS_NAMES = {
-    'arch': 'Arch Linux',
-    'debian': 'Debian',
-    'FreeBSD': 'FreeBSD',
-}
+# The output of --help and --list-tools will use the order of this dict.
+# Please keep it alphabetized.
+OS_NAMES = collections.OrderedDict([
+    ('arch', 'Arch Linux'),
+    ('debian', 'Debian'),
+    ('FreeBSD', 'FreeBSD'),
+])
 
 
 def tool_required(command):

-- 
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