PYTHON-1213 - Make decimal128 work with cdecimal

.evergreen/config.yml

@@ -345,6 +345,15 @@ functions:
           ${PREPARE_SHELL}
           PYTHON_BINARY=${PYTHON_BINARY} PROJECT_DIRECTORY=${PROJECT_DIRECTORY} sh ${PROJECT_DIRECTORY}/.evergreen/run-mockupdb-tests.sh
 
+  "run cdecimal tests":
+     - command: shell.exec
+       type: test
+       params:
+         working_dir: "src"
+         script: |
+           ${PREPARE_SHELL}
+           PYTHON_BINARY=${PYTHON_BINARY} sh ${PROJECT_DIRECTORY}/.evergreen/run-cdecimal-tests.sh
+
   "run doctests":
      - command: shell.exec
        type: test
@@ -681,6 +690,15 @@ tasks:
             TOPOLOGY: "replica_set"
         - func: "run mod_wsgi tests"
 
+    - name: "cdecimal"
+      tags: ["cdecimal"]
+      commands:
+        - func: "bootstrap mongo-orchestration"
+          vars:
+            VERSION: "latest"
+            TOPOLOGY: "server"
+        - func: "run cdecimal tests"
+
 # }}}
 
 
@@ -1316,6 +1334,15 @@ buildvariants:
   tasks:
      - name: "doctests"
 
+- matrix_name: "cdecimal"
+  matrix_spec: {python-version: ["2.6", "2.7"]}
+  display_name: "cdecimal ${python-version}"
+  batchtime: 10080  # 7 days
+  run_on:
+    - ubuntu1604-test
+  tasks:
+    - name: "cdecimal"
+
       # Platform notes
       # i386 builds of OpenSSL or Cyrus SASL are not available
       # Ubuntu14.04 only supports 2.6+ with SSL

.evergreen/run-cdecimal-tests.sh

@@ -0,0 +1,12 @@
+#!/bin/bash
+
+set -o xtrace
+set -o errexit
+
+virtualenv -p ${PYTHON_BINARY} cdecimaltest
+trap "deactivate; rm -rf cdecimaltest" EXIT HUP
+. cdecimaltest/bin/activate
+# No cdecimal tarballs on pypi.
+pip install http://www.bytereef.org/software/mpdecimal/releases/cdecimal-2.3.tar.gz
+python -c 'import sys; print(sys.version)'
+python cdecimal_test.py

bson/decimal128.py

@@ -84,9 +84,12 @@ _CTX_OPTIONS = {
               decimal.Inexact]
 }
 
-if _PY3:
+try:
+    # Python >= 3.3, cdecimal
+    decimal.Context(clamp=1)  # pylint: disable=unexpected-keyword-arg
     _CTX_OPTIONS['clamp'] = 1
-else:
+except TypeError:
+    # Python < 3.3
     _CTX_OPTIONS['_clamp'] = 1
 
 _DEC128_CTX = decimal.Context(**_CTX_OPTIONS.copy())
@@ -273,7 +276,7 @@ class Decimal128(object):
         elif (high & _NAN) == _NAN:
             return decimal.Decimal((sign, (), 'n'))
         elif (high & _INF) == _INF:
-            return decimal.Decimal((sign, (0,), 'F'))
+            return decimal.Decimal((sign, (), 'F'))
 
         if (high & _EXPONENT_MASK) == _EXPONENT_MASK:
             exponent = ((high & 0x1fffe00000000000) >> 47) - _EXPONENT_BIAS
@@ -296,7 +299,9 @@ class Decimal128(object):
         arr[0] = (high & mask) >> 48
 
         # Have to convert bytearray to bytes for python 2.6.
-        digits = [int(digit) for digit in str(_from_bytes(bytes(arr), 'big'))]
+        # cdecimal only accepts a tuple for digits.
+        digits = tuple(
+            int(digit) for digit in str(_from_bytes(bytes(arr), 'big')))
 
         with decimal.localcontext(_DEC128_CTX) as ctx:
             return ctx.create_decimal((sign, digits, exponent))

cdecimal_test.py

@@ -0,0 +1,66 @@
+# Copyright 2017 MongoDB, Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Test PyMongo with cdecimal monkey-patched over stdlib decimal."""
+
+import getopt
+import sys
+
+try:
+    import cdecimal
+    _HAVE_CDECIMAL = True
+except ImportError:
+    _HAVE_CDECIMAL = False
+
+
+def run(args):
+    """Run tests with cdecimal monkey-patched over stdlib decimal."""
+    # Monkey-patch.
+    sys.modules['decimal'] = cdecimal
+
+    # Run the tests.
+    sys.argv[:] = ['setup.py', 'test'] + list(args)
+    import setup
+
+
+def main():
+    """Parse options and run tests."""
+    usage = """python %s
+
+Test PyMongo with cdecimal monkey-patched over decimal.""" % (sys.argv[0],)
+
+    try:
+        opts, args = getopt.getopt(
+            sys.argv[1:], "h", ["help"])
+    except getopt.GetoptError as err:
+        print(str(err))
+        print(usage)
+        sys.exit(2)
+
+    for option_name, _ in opts:
+        if option_name in ("-h", "--help"):
+            print(usage)
+            sys.exit()
+        else:
+            assert False, "unhandled option"
+
+    if not _HAVE_CDECIMAL:
+        print("The cdecimal package is not installed.")
+        sys.exit(1)
+
+    run(args)  # Command line args to setup.py, like what test to run.
+
+
+if __name__ == '__main__':
+    main()