Remove unnecessary compatibility shims for Python 2 (#498)

As the project is Python 3 only, can remove the compatibility shims in
compat.py.

Type checking has been simplified where it can:
  - str is iterable
  - bytes is iterable
  - use isinstance instead of issubclass

The remaining function bytes_from_int() has been moved to utils.py.

12 files changed, 46 insertions, 83 deletions

diff --git a/docs/api.rst b/docs/api.rst
index 3f66173..6ca0b62 100644
--- a/docs/api.rst
+++ b/docs/api.rst
@@ -52,7 +52,7 @@ API Reference
                 Use ``verify_exp`` instead
 
 
-    :param str|iterable audience: optional, the value for ``verify_aud`` check
+    :param iterable audience: optional, the value for ``verify_aud`` check
     :param str issuer: optional, the value for ``verify_iss`` check
     :param int|float leeway: a time margin in seconds for the expiration check
     :param bool verify_expiration:
diff --git a/jwt/__main__.py b/jwt/__main__.py
index 4fd3d33..9ed8b71 100644
--- a/jwt/__main__.py
+++ b/jwt/__main__.py
@@ -71,8 +71,13 @@ def decode_payload(args):
                 raise OSError("Cannot read from stdin: terminal not a TTY")
 
         token = token.encode("utf-8")
-        data = decode(token, key=args.key, verify=args.verify,
-                      audience=args.audience, issuer=args.issuer)
+        data = decode(
+            token,
+            key=args.key,
+            verify=args.verify,
+            audience=args.audience,
+            issuer=args.issuer,
+        )
 
         return json.dumps(data)
 
diff --git a/jwt/algorithms.py b/jwt/algorithms.py
index 10ef680..3a7040c 100644
--- a/jwt/algorithms.py
+++ b/jwt/algorithms.py
@@ -2,7 +2,6 @@ import hashlib
 import hmac
 import json
 
-from .compat import constant_time_compare, string_types
 from .exceptions import InvalidKeyError
 from .utils import (
     base64url_decode,
@@ -216,7 +215,7 @@ class HMACAlgorithm(Algorithm):
         return hmac.new(key, msg, self.hash_alg).digest()
 
     def verify(self, msg, key, sig):
-        return constant_time_compare(sig, self.sign(msg, key))
+        return hmac.compare_digest(sig, self.sign(msg, key))
 
 
 if has_crypto:  # noqa: C901
@@ -238,7 +237,7 @@ if has_crypto:  # noqa: C901
             if isinstance(key, RSAPrivateKey) or isinstance(key, RSAPublicKey):
                 return key
 
-            if isinstance(key, string_types):
+            if isinstance(key, (bytes, str)):
                 key = force_bytes(key)
 
                 try:
@@ -395,7 +394,7 @@ if has_crypto:  # noqa: C901
             ):
                 return key
 
-            if isinstance(key, string_types):
+            if isinstance(key, (bytes, str)):
                 key = force_bytes(key)
 
                 # Attempt to load key. We don't know if it's
diff --git a/jwt/api_jws.py b/jwt/api_jws.py
index ef5d7ec..287dbf4 100644
--- a/jwt/api_jws.py
+++ b/jwt/api_jws.py
@@ -1,10 +1,10 @@
 import binascii
 import json
 import warnings
+from collections.abc import Mapping
 
 from .algorithms import requires_cryptography  # NOQA
 from .algorithms import Algorithm, get_default_algorithms, has_crypto
-from .compat import Mapping, binary_type, string_types, text_type
 from .exceptions import (
     DecodeError,
     InvalidAlgorithmError,
@@ -178,12 +178,12 @@ class PyJWS:
         return headers
 
     def _load(self, jwt):
-        if isinstance(jwt, text_type):
+        if isinstance(jwt, str):
             jwt = jwt.encode("utf-8")
 
-        if not issubclass(type(jwt), binary_type):
+        if not isinstance(jwt, bytes):
             raise DecodeError(
-                "Invalid token type. Token must be a {}".format(binary_type)
+                "Invalid token type. Token must be a {}".format(bytes)
             )
 
         try:
@@ -249,7 +249,7 @@ class PyJWS:
             self._validate_kid(headers["kid"])
 
     def _validate_kid(self, kid):
-        if not isinstance(kid, string_types):
+        if not isinstance(kid, (bytes, str)):
             raise InvalidTokenError("Key ID header parameter must be a string")
 
 
diff --git a/jwt/api_jwt.py b/jwt/api_jwt.py
index 4289b40..b42a4d6 100644
--- a/jwt/api_jwt.py
+++ b/jwt/api_jwt.py
@@ -1,11 +1,11 @@
 import json
 import warnings
 from calendar import timegm
+from collections.abc import Iterable, Mapping
 from datetime import datetime, timedelta
 
 from .algorithms import Algorithm, get_default_algorithms  # NOQA
 from .api_jws import PyJWS
-from .compat import Iterable, Mapping, string_types
 from .exceptions import (
     DecodeError,
     ExpiredSignatureError,
@@ -149,8 +149,8 @@ class PyJWT(PyJWS):
         if isinstance(leeway, timedelta):
             leeway = leeway.total_seconds()
 
-        if not isinstance(audience, (string_types, type(None), Iterable)):
-            raise TypeError("audience must be a string, iterable, or None")
+        if not isinstance(audience, (type(None), Iterable)):
+            raise TypeError("audience must be an iterable or None")
 
         self._validate_required_claims(payload, options)
 
@@ -220,14 +220,14 @@ class PyJWT(PyJWS):
 
         audience_claims = payload["aud"]
 
-        if isinstance(audience_claims, string_types):
+        if isinstance(audience_claims, (bytes, str)):
             audience_claims = [audience_claims]
         if not isinstance(audience_claims, list):
             raise InvalidAudienceError("Invalid claim format in token")
-        if any(not isinstance(c, string_types) for c in audience_claims):
+        if any(not isinstance(c, (bytes, str)) for c in audience_claims):
             raise InvalidAudienceError("Invalid claim format in token")
 
-        if isinstance(audience, string_types):
+        if isinstance(audience, (bytes, str)):
             audience = [audience]
 
         if not any(aud in audience_claims for aud in audience):
diff --git a/jwt/compat.py b/jwt/compat.py
deleted file mode 100644
index b4fec15..0000000
--- a/jwt/compat.py
+++ /dev/null
@@ -1,30 +0,0 @@
-"""
-The `compat` module provides support for backwards compatibility with older
-versions of python, and compatibility wrappers around optional packages.
-"""
-# flake8: noqa
-import hmac
-
-text_type = str
-binary_type = bytes
-string_types = (str, bytes)
-
-try:
-    # Importing ABCs from collections will be removed in PY3.8
-    from collections.abc import Iterable, Mapping
-except ImportError:
-    from collections import Iterable, Mapping
-
-
-constant_time_compare = hmac.compare_digest
-
-
-def bytes_from_int(val):
-    remaining = val
-    byte_length = 0
-
-    while remaining != 0:
-        remaining = remaining >> 8
-        byte_length += 1
-
-    return val.to_bytes(byte_length, "big", signed=False)
diff --git a/jwt/contrib/algorithms/py_ecdsa.py b/jwt/contrib/algorithms/py_ecdsa.py
index 5b878f5..3f5fa76 100644
--- a/jwt/contrib/algorithms/py_ecdsa.py
+++ b/jwt/contrib/algorithms/py_ecdsa.py
@@ -6,7 +6,6 @@ import hashlib
 import ecdsa
 
 from jwt.algorithms import Algorithm
-from jwt.compat import string_types, text_type
 
 
 class ECAlgorithm(Algorithm):
@@ -33,8 +32,8 @@ class ECAlgorithm(Algorithm):
         ):
             return key
 
-        if isinstance(key, string_types):
-            if isinstance(key, text_type):
+        if isinstance(key, (bytes, str)):
+            if isinstance(key, str):
                 key = key.encode("utf-8")
 
             # Attempt to load key. We don't know if it's
diff --git a/jwt/contrib/algorithms/py_ed25519.py b/jwt/contrib/algorithms/py_ed25519.py
index 1a1d4da..a86000a 100644
--- a/jwt/contrib/algorithms/py_ed25519.py
+++ b/jwt/contrib/algorithms/py_ed25519.py
@@ -15,7 +15,6 @@ from cryptography.hazmat.primitives.serialization import (
 )
 
 from jwt.algorithms import Algorithm
-from jwt.compat import string_types, text_type
 
 
 class Ed25519Algorithm(Algorithm):
@@ -33,8 +32,8 @@ class Ed25519Algorithm(Algorithm):
         if isinstance(key, (Ed25519PrivateKey, Ed25519PublicKey)):
             return key
 
-        if isinstance(key, string_types):
-            if isinstance(key, text_type):
+        if isinstance(key, (bytes, str)):
+            if isinstance(key, str):
                 key = key.encode("utf-8")
             str_key = key.decode("utf-8")
 
diff --git a/jwt/contrib/algorithms/pycrypto.py b/jwt/contrib/algorithms/pycrypto.py
index d58e907..0fb5871 100644
--- a/jwt/contrib/algorithms/pycrypto.py
+++ b/jwt/contrib/algorithms/pycrypto.py
@@ -5,7 +5,6 @@ from Crypto.PublicKey import RSA
 from Crypto.Signature import PKCS1_v1_5
 
 from jwt.algorithms import Algorithm
-from jwt.compat import string_types, text_type
 
 
 class RSAAlgorithm(Algorithm):
@@ -30,8 +29,8 @@ class RSAAlgorithm(Algorithm):
         if isinstance(key, RSA._RSAobj):
             return key
 
-        if isinstance(key, string_types):
-            if isinstance(key, text_type):
+        if isinstance(key, (bytes, str)):
+            if isinstance(key, str):
                 key = key.encode("utf-8")
 
             key = RSA.importKey(key)
diff --git a/jwt/utils.py b/jwt/utils.py
index cc7f56c..0e8f210 100644
--- a/jwt/utils.py
+++ b/jwt/utils.py
@@ -2,8 +2,6 @@ import base64
 import binascii
 import struct
 
-from .compat import binary_type, bytes_from_int, text_type
-
 try:
     from cryptography.hazmat.primitives.asymmetric.utils import (
         decode_dss_signature,
@@ -14,25 +12,25 @@ except ImportError:
 
 
 def force_unicode(value):
-    if isinstance(value, binary_type):
+    if isinstance(value, bytes):
         return value.decode("utf-8")
-    elif isinstance(value, text_type):
+    elif isinstance(value, str):
         return value
     else:
         raise TypeError("Expected a string value")
 
 
 def force_bytes(value):
-    if isinstance(value, text_type):
+    if isinstance(value, str):
         return value.encode("utf-8")
-    elif isinstance(value, binary_type):
+    elif isinstance(value, bytes):
         return value
     else:
         raise TypeError("Expected a string value")
 
 
 def base64url_decode(input):
-    if isinstance(input, text_type):
+    if isinstance(input, str):
         input = input.encode("ascii")
 
     rem = len(input) % 4
@@ -60,7 +58,7 @@ def to_base64url_uint(val):
 
 
 def from_base64url_uint(val):
-    if isinstance(val, text_type):
+    if isinstance(val, str):
         val = val.encode("ascii")
 
     data = base64url_decode(val)
@@ -92,6 +90,17 @@ def bytes_to_number(string):
     return int(binascii.b2a_hex(string), 16)
 
 
+def bytes_from_int(val):
+    remaining = val
+    byte_length = 0
+
+    while remaining != 0:
+        remaining = remaining >> 8
+        byte_length += 1
+
+    return val.to_bytes(byte_length, "big", signed=False)
+
+
 def der_to_raw_signature(der_sig, curve):
     num_bits = curve.key_size
     num_bytes = (num_bits + 7) // 8
diff --git a/tests/test_api_jwt.py b/tests/test_api_jwt.py
index 829f519..50c748b 100644
--- a/tests/test_api_jwt.py
+++ b/tests/test_api_jwt.py
@@ -99,7 +99,7 @@ class TestJWT:
             jwt.decode(example_jwt, secret, audience=1)
 
         exception = context.value
-        assert str(exception) == "audience must be a string, iterable, or None"
+        assert str(exception) == "audience must be an iterable or None"
 
     def test_decode_with_nonlist_aud_claim_throws_exception(self, jwt):
         secret = "secret"
diff --git a/tests/test_compat.py b/tests/test_compat.py
deleted file mode 100644
index 7a7516c..0000000
--- a/tests/test_compat.py
+++ /dev/null
@@ -1,17 +0,0 @@
-from jwt.compat import constant_time_compare
-from jwt.utils import force_bytes
-
-
-class TestCompat:
-    def test_constant_time_compare_returns_true_if_same(self):
-        assert constant_time_compare(force_bytes("abc"), force_bytes("abc"))
-
-    def test_constant_time_compare_returns_false_if_diff_lengths(self):
-        assert not constant_time_compare(
-            force_bytes("abc"), force_bytes("abcd")
-        )
-
-    def test_constant_time_compare_returns_false_if_totally_different(self):
-        assert not constant_time_compare(
-            force_bytes("abcd"), force_bytes("efgh")
-        )