From 0f3d256ebfe9e2f0adaecc96b8840d8d2328dfca Mon Sep 17 00:00:00 2001
From: Adam Porter <adam@alphapapa.net>
Date: Wed, 30 Oct 2019 08:45:17 -0500
Subject: [PATCH] Add: parse-args function

Closes #1719.
---
 NEWS.rst                   |  1 +
 docs/language/core.rst     | 23 +++++++++++++++++++++++
 hy/core/language.hy        | 15 ++++++++++++++-
 tests/native_tests/core.hy |  9 +++++++++
 4 files changed, 47 insertions(+), 1 deletion(-)

diff --git a/NEWS.rst b/NEWS.rst
index 40bd19b..2053b1f 100644
--- a/NEWS.rst
+++ b/NEWS.rst
@@ -18,6 +18,7 @@ New Features
 * All augmented assignment operators (except `%=` and `^=`) now allow
   more than two arguments.
 * PEP 3107 and PEP 526 function and variable annotations are now supported.
+* Added function ``parse-args`` which parses arguments with ``argparse``.
 
 Other Breaking Changes
 ------------------------------
diff --git a/docs/language/core.rst b/docs/language/core.rst
index cabb420..6cb8c4d 100644
--- a/docs/language/core.rst
+++ b/docs/language/core.rst
@@ -786,6 +786,29 @@ Returns ``True`` if *x* is odd. Raises ``TypeError`` if
    => (odd? 0)
    False
 
+.. _parse-args:
+
+parse-args
+----------
+
+Usage: ``(parse-args spec &optional args &kwargs parser-args)``
+
+Return arguments namespace parsed from *args* or ``sys.argv`` with
+:py:meth:`argparse.ArgumentParser.parse_args` according to *spec*.
+
+*spec* should be a list of arguments which will be passed to repeated
+calls to :py:meth:`argparse.ArgumentParser.add_argument`.  *parser-args*
+may be a list of keyword arguments to pass to the
+:py:class:`argparse.ArgumentParser` constructor.
+
+.. code-block:: hy
+
+    => (parse-args [["strings" :nargs "+" :help "Strings"]
+                    ["-n" "--numbers" :action "append" :type 'int :help "Numbers"]]
+                   ["a" "b" "-n" "1" "-n" "2"]
+                   :description "Parse strings and numbers from args")
+    Namespace(numbers=[1, 2], strings=['a', 'b'])
+
 .. _partition-fn:
 
 partition
diff --git a/hy/core/language.hy b/hy/core/language.hy
index 80cba83..fa82185 100644
--- a/hy/core/language.hy
+++ b/hy/core/language.hy
@@ -391,6 +391,19 @@ Even objects with the __name__ magic will work."
     False
     (or a b)))
 
+(defn parse-args [spec &optional args &kwargs parser-args]
+  "Return arguments namespace parsed from `args` or `sys.argv` with `argparse.ArgumentParser.parse-args` according to `spec`.
+
+`spec` should be a list of arguments to pass to repeated calls to
+`argparse.ArgumentParser.add-argument`.  `parser-args` may be a list
+of keyword arguments to pass to the `argparse.ArgumentParser`
+constructor."
+  (import argparse)
+  (setv parser (argparse.ArgumentParser #** parser-args))
+  (for [arg spec]
+    (eval `(.add-argument parser ~@arg)))
+  (.parse-args parser args))
+
 (setv EXPORTS
   '[*map accumulate butlast calling-module calling-module-name chain coll?
     combinations comp complement compress constantly count cycle dec distinct
@@ -399,6 +412,6 @@ Even objects with the __name__ magic will work."
     integer? integer-char? interleave interpose islice iterable?
     iterate iterator? juxt keyword keyword? last list? macroexpand
     macroexpand-1 mangle merge-with multicombinations name neg? none? nth
-    numeric? odd? partition permutations pos? product read read-str
+    numeric? odd? parse-args partition permutations pos? product read read-str
     remove repeat repeatedly rest reduce second some string? symbol?
     take take-nth take-while tuple? unmangle xor tee zero? zip-longest])
diff --git a/tests/native_tests/core.hy b/tests/native_tests/core.hy
index b961f78..e5aad68 100644
--- a/tests/native_tests/core.hy
+++ b/tests/native_tests/core.hy
@@ -478,6 +478,15 @@ result['y in globals'] = 'y' in globals()")
   (assert-false (odd? 0))
   (assert-requires-num odd?))
 
+(defn test-parse-args []
+  "NATIVE: testing the parse-args function"
+  (setv parsed-args (parse-args [["strings" :nargs "+" :help "Strings"]
+                                 ["-n" "--numbers" :action "append" :type 'int :help "Numbers"]]
+                                ["a" "b" "-n" "1" "-n" "2"]
+                                :description "Parse strings and numbers from args"))
+  (assert-equal parsed-args.strings ["a" "b"])
+  (assert-equal parsed-args.numbers [1 2]))
+
 (defn test-partition []
   "NATIVE: testing the partition function"
   (setv ten (range 10))