Added mypy for static type checking

8 files changed, 119 insertions, 32 deletions

diff --git a/.gitignore b/.gitignore
index 1f5a640..e31443a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -12,6 +12,7 @@
 .coverage
 .coverage.*
 .cache/
+.mypy_cache/
 .pytest_cache/
 __pycache__/
 
diff --git a/Pipfile b/Pipfile
index a03274c..b22cab3 100644
--- a/Pipfile
+++ b/Pipfile
@@ -13,7 +13,8 @@ Sphinx = "*"
 coveralls = "*"
 pytest = "*"
 pytest-cov = "*"
-pathlib2 = {version = "*", markers="python_version < '3.6'"}
+pathlib2 = {version = "*",markers = "python_version < '3.6'"}
+mypy = "*"
 
 [requires]
 python_version = "3.7"
diff --git a/Pipfile.lock b/Pipfile.lock
index 6a399e6..9ec9947 100644
--- a/Pipfile.lock
+++ b/Pipfile.lock
@@ -1,7 +1,7 @@
 {
     "_meta": {
         "hash": {
-            "sha256": "65309370bad59af42cbf3b538e9a050dece94209b8b9657eb4e9f1ca8feedda4"
+            "sha256": "376fdc997e7b1f113fdc6c27ce5d1ba88f01a3dbe64f03d54132e5f7b5cd24a4"
         },
         "pipfile-spec": 6,
         "requires": {
@@ -210,6 +210,30 @@
             ],
             "version": "==7.2.0"
         },
+        "mypy": {
+            "hashes": [
+                "sha256:0107bff4f46a289f0e4081d59b77cef1c48ea43da5a0dbf0005d54748b26df2a",
+                "sha256:07957f5471b3bb768c61f08690c96d8a09be0912185a27a68700f3ede99184e4",
+                "sha256:10af62f87b6921eac50271e667cc234162a194e742d8e02fc4ddc121e129a5b0",
+                "sha256:11fd60d2f69f0cefbe53ce551acf5b1cec1a89e7ce2d47b4e95a84eefb2899ae",
+                "sha256:15e43d3b1546813669bd1a6ec7e6a11d2888db938e0607f7b5eef6b976671339",
+                "sha256:352c24ba054a89bb9a35dd064ee95ab9b12903b56c72a8d3863d882e2632dc76",
+                "sha256:437020a39417e85e22ea8edcb709612903a9924209e10b3ec6d8c9f05b79f498",
+                "sha256:49925f9da7cee47eebf3420d7c0e00ec662ec6abb2780eb0a16260a7ba25f9c4",
+                "sha256:6724fcd5777aa6cebfa7e644c526888c9d639bd22edd26b2a8038c674a7c34bd",
+                "sha256:7a17613f7ea374ab64f39f03257f22b5755335b73251d0d253687a69029701ba",
+                "sha256:cdc1151ced496ca1496272da7fc356580e95f2682be1d32377c22ddebdf73c91"
+            ],
+            "index": "pypi",
+            "version": "==0.720"
+        },
+        "mypy-extensions": {
+            "hashes": [
+                "sha256:37e0e956f41369209a3d5f34580150bcacfabaa57b33a15c0b25f4b5725e0812",
+                "sha256:b16cabe759f55e3409a7d231ebd2841378fb0c27a5d1994719e340e4f429ac3e"
+            ],
+            "version": "==0.4.1"
+        },
         "packaging": {
             "hashes": [
                 "sha256:a7ac867b97fdc07ee80a8058fe4435ccd274ecc3b0ed61d852d7d53055528cf9",
@@ -362,6 +386,34 @@
             "index": "pypi",
             "version": "==3.13.2"
         },
+        "typed-ast": {
+            "hashes": [
+                "sha256:18511a0b3e7922276346bcb47e2ef9f38fb90fd31cb9223eed42c85d1312344e",
+                "sha256:262c247a82d005e43b5b7f69aff746370538e176131c32dda9cb0f324d27141e",
+                "sha256:2b907eb046d049bcd9892e3076c7a6456c93a25bebfe554e931620c90e6a25b0",
+                "sha256:354c16e5babd09f5cb0ee000d54cfa38401d8b8891eefa878ac772f827181a3c",
+                "sha256:4e0b70c6fc4d010f8107726af5fd37921b666f5b31d9331f0bd24ad9a088e631",
+                "sha256:630968c5cdee51a11c05a30453f8cd65e0cc1d2ad0d9192819df9978984529f4",
+                "sha256:66480f95b8167c9c5c5c87f32cf437d585937970f3fc24386f313a4c97b44e34",
+                "sha256:71211d26ffd12d63a83e079ff258ac9d56a1376a25bc80b1cdcdf601b855b90b",
+                "sha256:95bd11af7eafc16e829af2d3df510cecfd4387f6453355188342c3e79a2ec87a",
+                "sha256:bc6c7d3fa1325a0c6613512a093bc2a2a15aeec350451cbdf9e1d4bffe3e3233",
+                "sha256:cc34a6f5b426748a507dd5d1de4c1978f2eb5626d51326e43280941206c209e1",
+                "sha256:d755f03c1e4a51e9b24d899561fec4ccaf51f210d52abdf8c07ee2849b212a36",
+                "sha256:d7c45933b1bdfaf9f36c579671fec15d25b06c8398f113dab64c18ed1adda01d",
+                "sha256:d896919306dd0aa22d0132f62a1b78d11aaf4c9fc5b3410d3c666b818191630a",
+                "sha256:ffde2fbfad571af120fcbfbbc61c72469e72f550d676c3342492a9dfdefb8f12"
+            ],
+            "version": "==1.4.0"
+        },
+        "typing-extensions": {
+            "hashes": [
+                "sha256:2ed632b30bb54fc3941c382decfd0ee4148f5c591651c9272473fea2c6397d95",
+                "sha256:b1edbbf0652660e32ae780ac9433f4231e7339c7f9a8057d0f042fcbcea49b87",
+                "sha256:d8179012ec2c620d3791ca6fe2bf7979d979acdbef1fca0bc56b37411db682ed"
+            ],
+            "version": "==3.7.4"
+        },
         "urllib3": {
             "hashes": [
                 "sha256:b246607a25ac80bedac05c6f282e3cdaf3afb65420fd024ac94435cabe6e18d1",
diff --git a/rsa/cli.py b/rsa/cli.py
index 77bd4ee..cbf3f97 100644
--- a/rsa/cli.py
+++ b/rsa/cli.py
@@ -21,9 +21,11 @@ These scripts are called by the executables defined in setup.py.
 
 import abc
 import sys
+import typing
 from optparse import OptionParser
 
 import rsa
+import rsa.key
 import rsa.pkcs1
 
 HASH_METHODS = sorted(rsa.pkcs1.HASH_METHODS.keys())
@@ -84,14 +86,12 @@ def keygen():
         sys.stdout.buffer.write(data)
 
 
-class CryptoOperation(object):
+class CryptoOperation(metaclass=abc.ABCMeta):
     """CLI callable that operates with input, output, and a key."""
 
-    __metaclass__ = abc.ABCMeta
-
     keyname = 'public'  # or 'private'
     usage = 'usage: %%prog [options] %(keyname)s_key'
-    description = None
+    description = ''
     operation = 'decrypt'
     operation_past = 'decrypted'
     operation_progressive = 'decrypting'
@@ -102,7 +102,7 @@ class CryptoOperation(object):
     expected_cli_args = 1
     has_output = True
 
-    key_class = rsa.PublicKey
+    key_class = rsa.PublicKey  # type: typing.Type[rsa.key.AbstractKey]
 
     def __init__(self):
         self.usage = self.usage % self.__class__.__dict__
diff --git a/setup.cfg b/setup.cfg
index ed8a958..c5601b1 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -3,3 +3,16 @@ universal = 1
 
 [metadata]
 license_file = LICENSE
+
+[flake8]
+max-line-length = 100
+
+[pep8]
+max-line-length = 100
+
+[mypy]
+python_version = 3.7
+warn_unused_ignores = True
+ignore_missing_imports = True
+follow_imports = skip
+incremental = True
diff --git a/tests/test_cli.py b/tests/test_cli.py
index 7cf7ed4..1cd92c2 100644
--- a/tests/test_cli.py
+++ b/tests/test_cli.py
@@ -4,41 +4,37 @@ Unit tests for CLI entry points.
 
 from __future__ import print_function
 
-import unittest
-import sys
 import functools
-from contextlib import contextmanager
-
+import io
 import os
-from io import StringIO, BytesIO
+import sys
+import typing
+import unittest
+from contextlib import contextmanager, redirect_stdout, redirect_stderr
 
 import rsa
 import rsa.cli
 import rsa.util
 
 
-def make_buffer() -> StringIO:
-    buf = StringIO()
-    buf.buffer = BytesIO()
-    return buf
+@contextmanager
+def captured_output() -> typing.Generator:
+    """Captures output to stdout and stderr"""
 
+    # According to mypy, we're not supposed to change buf_out.buffer.
+    # However, this is just a test, and it works, hence the 'type: ignore'.
+    buf_out = io.StringIO()
+    buf_out.buffer = io.BytesIO()  # type: ignore
 
-def get_bytes_out(out: StringIO) -> bytes:
-    # Python 3.x writes 'bytes' to stdout.buffer
-    return out.buffer.getvalue()
+    buf_err = io.StringIO()
+    buf_err.buffer = io.BytesIO()  # type: ignore
 
+    with redirect_stdout(buf_out), redirect_stderr(buf_err):
+        yield buf_out, buf_err
 
-@contextmanager
-def captured_output():
-    """Captures output to stdout and stderr"""
 
-    new_out, new_err = make_buffer(), make_buffer()
-    old_out, old_err = sys.stdout, sys.stderr
-    try:
-        sys.stdout, sys.stderr = new_out, new_err
-        yield new_out, new_err
-    finally:
-        sys.stdout, sys.stderr = old_out, old_err
+def get_bytes_out(buf) -> bytes:
+    return buf.buffer.getvalue()
 
 
 @contextmanager
diff --git a/tests/test_mypy.py b/tests/test_mypy.py
new file mode 100644
index 0000000..c2a9745
--- /dev/null
+++ b/tests/test_mypy.py
@@ -0,0 +1,27 @@
+import pathlib
+import unittest
+
+import mypy.api
+
+test_modules = ['rsa', 'tests']
+
+
+class MypyRunnerTest(unittest.TestCase):
+    def test_run_mypy(self):
+        proj_root = pathlib.Path(__file__).parent.parent
+        args = ['--incremental', '--ignore-missing-imports'] + [str(proj_root / dirname) for dirname
+                                                                in test_modules]
+
+        result = mypy.api.run(args)
+
+        stdout, stderr, status = result
+
+        messages = []
+        if stderr:
+            messages.append(stderr)
+        if stdout:
+            messages.append(stdout)
+        if status:
+            messages.append('Mypy failed with status %d' % status)
+        if messages:
+            self.fail('\n'.join(['Mypy errors:'] + messages))
diff --git a/tox.ini b/tox.ini
index 0401412..c9f1370 100644
--- a/tox.ini
+++ b/tox.ini
@@ -15,6 +15,3 @@ commands=
 commands=
     pipenv install --dev --ignore-pipfile
     pipenv run py.test --doctest-modules rsa tests
-
-[pep8]
-max-line-length = 100