alot/utils/argparse: Add a new argparse validators infrastructure

This adds a new argparse.Action class validates input using a new
keyword argument that takes a validator function. This will allow us to
replace the use the type keyword as a validator, which is both more
correct, and frees up the type keyword to do what it's actually meant to
do, convert the input from one type to another.

It also adds 3 new validator functions that will be enabled in the next
commit. One that checks for a required file, one that checks for an
optional directory, and one that looks for a required file, fifo, or
block special device (/dev/null).

1 files changed, 154 insertions, 0 deletions

diff --git a/tests/utils/argparse_test.py b/tests/utils/argparse_test.py
new file mode 100644
index 00000000..b76e96ec
--- /dev/null
+++ b/tests/utils/argparse_test.py
@@ -0,0 +1,154 @@
+# encoding=utf-8
+# Copyright © 2017 Dylan Baker
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+"""Tests for alot.utils.argparse"""
+
+from __future__ import absolute_import
+
+import argparse
+import contextlib
+import os
+import shutil
+import tempfile
+import unittest
+
+from alot.utils import argparse as cargparse
+
+
+class TestValidatedStore(unittest.TestCase):
+    """Tests for the ValidatedStore action class."""
+
+    def _argparse(self, args):
+        """Create an argparse instance with a validator."""
+
+        def validator(args):
+            if args == 'fail':
+                raise cargparse.ValidationFailed
+
+        parser = argparse.ArgumentParser()
+        parser.add_argument(
+            'foo',
+            action=cargparse.ValidatedStoreAction,
+            validator=validator)
+        return parser.parse_args(args)
+
+    def test_validates(self):
+        # Arparse will raise a SystemExit (calls sys.exit) rather than letting
+        # the exception cause the program to close.
+        with self.assertRaises(SystemExit):
+            self._argparse(['fail'])
+
+
+@contextlib.contextmanager
+def temporary_directory(suffix='', prefix='', dir=None):
+    """Python3 interface implementation.
+
+    Python3 provides a class that can be used as a context manager, which
+    creates a temporary directory and removes it when the context manager
+    exits. This function emulates enough of the interface of
+    TemporaryDirectory, for this module to use, and is designed as a drop in
+    replacement that can be replaced after the python3 port.
+
+    The only user visible difference is that this does not implement the
+    cleanup method that TemporaryDirectory does.
+    """
+    directory = tempfile.mkdtemp(suffix=suffix, prefix=prefix, dir=dir)
+    yield directory
+    shutil.rmtree(directory)
+
+
+class TestRequireFile(unittest.TestCase):
+    """Tests for the require_file validator."""
+
+    def test_doesnt_exist(self):
+        with temporary_directory() as d:
+            with self.assertRaises(cargparse.ValidationFailed):
+                cargparse.require_file(os.path.join(d, 'doesnt-exist'))
+
+    def test_dir(self):
+        with temporary_directory() as d:
+            with self.assertRaises(cargparse.ValidationFailed):
+                cargparse.require_file(d)
+
+    def test_file(self):
+        with tempfile.NamedTemporaryFile() as f:
+            cargparse.require_file(f.name)
+
+    def test_char_special(self):
+        with self.assertRaises(cargparse.ValidationFailed):
+            cargparse.require_file('/dev/null')
+
+    def test_fifo(self):
+        with temporary_directory() as d:
+            path = os.path.join(d, 'fifo')
+            os.mkfifo(path)
+            with self.assertRaises(cargparse.ValidationFailed):
+                cargparse.require_file(path)
+
+
+class TestRequireDir(unittest.TestCase):
+    """Tests for the require_dir validator."""
+
+    def test_doesnt_exist(self):
+        with temporary_directory() as d:
+            with self.assertRaises(cargparse.ValidationFailed):
+                cargparse.require_dir(os.path.join(d, 'doesnt-exist'))
+
+    def test_dir(self):
+        with temporary_directory() as d:
+            cargparse.require_dir(d)
+
+    def test_file(self):
+        with tempfile.NamedTemporaryFile() as f:
+            with self.assertRaises(cargparse.ValidationFailed):
+                cargparse.require_dir(f.name)
+
+    def test_char_special(self):
+        with self.assertRaises(cargparse.ValidationFailed):
+            cargparse.require_dir('/dev/null')
+
+    def test_fifo(self):
+        with temporary_directory() as d:
+            path = os.path.join(d, 'fifo')
+            os.mkfifo(path)
+            with self.assertRaises(cargparse.ValidationFailed):
+                cargparse.require_dir(path)
+
+
+class TestOptionalFileLike(unittest.TestCase):
+    """Tests for the optional_file_like validator."""
+
+    def test_doesnt_exist(self):
+        with temporary_directory() as d:
+            cargparse.optional_file_like(os.path.join(d, 'doesnt-exist'))
+
+    def test_dir(self):
+        with temporary_directory() as d:
+            with self.assertRaises(cargparse.ValidationFailed):
+                cargparse.optional_file_like(d)
+
+    def test_file(self):
+        with tempfile.NamedTemporaryFile() as f:
+            cargparse.optional_file_like(f.name)
+
+    def test_char_special(self):
+        cargparse.optional_file_like('/dev/null')
+
+    def test_fifo(self):
+        with temporary_directory() as d:
+            path = os.path.join(d, 'fifo')
+            os.mkfifo(path)
+            cargparse.optional_file_like(path)