add zsh completion script (#150)

Makefile

@@ -24,7 +24,7 @@ test:
 executable:
 	scripts/pyinstaller.py
 
-completion: data/completion/gallery-dl
+completion: data/completion/gallery-dl data/completion/_gallery-dl
 
 man: data/man/gallery-dl.1 data/man/gallery-dl.conf.5
 
@@ -39,5 +39,8 @@ data/man/gallery-dl.1: gallery_dl/option.py gallery_dl/version.py scripts/man.py
 data/man/gallery-dl.conf.5: docs/configuration.rst gallery_dl/version.py scripts/man.py
 	$(PYTHON) scripts/man.py
 
-data/completion/gallery-dl: gallery_dl/option.py scripts/bash_completion.py
-	$(PYTHON) scripts/bash_completion.py
+data/completion/gallery-dl: gallery_dl/option.py scripts/completion_bash.py
+	$(PYTHON) scripts/completion_bash.py
+
+data/completion/_gallery-dl: gallery_dl/option.py scripts/completion_zsh.py
+	$(PYTHON) scripts/completion_zsh.py

scripts/completion_zsh.py

@@ -0,0 +1,51 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+
+# Copyright 2020 Mike Fährmann
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 2 as
+# published by the Free Software Foundation.
+
+"""Generate bash completion script from gallery-dl's argument parser"""
+
+import util
+from gallery_dl import option
+
+
+TEMPLATE = """#compdef gallery-dl
+
+local curcontext="$curcontext"
+typeset -A opt_args
+
+local rc=1
+_arguments -C -S \\
+%(opts)s \\
+'*:URL:_urls' && rc=0
+
+return rc
+"""
+
+opts = []
+for action in option.build_parser()._actions:
+
+    if not action.option_strings:
+        continue
+    elif len(action.option_strings) == 1:
+        opt = action.option_strings[0]
+    else:
+        opt = "{" + ",".join(action.option_strings) + "}"
+
+    opt += "'[" + action.help.replace("'", '"') + "]'"
+
+    if action.metavar:
+        opt += ":'<" + action.metavar.lower() + ">'"
+        if action.metavar in ("FILE", "CFG", "DEST"):
+            opt += ":_files"
+
+    opts.append(opt)
+
+
+PATH = util.path("data/completion/_gallery-dl")
+with open(PATH, "w", encoding="utf-8") as file:
+    file.write(TEMPLATE % {"opts": " \\\n".join(opts)})

setup.py

@@ -37,6 +37,7 @@ def check_file(fname):
     (path, [f for f in files if check_file(f)])
     for (path, files) in [
         ("share/bash-completion/completions", ["data/completion/gallery-dl"]),
+        ("share/zsh/site-functions"         , ["data/completion/_gallery-dl"]),
         ("share/man/man1"                   , ["data/man/gallery-dl.1"]),
         ("share/man/man5"                   , ["data/man/gallery-dl.conf.5"]),
     ]