bpo-36025: Fix PyDate_FromTimestamp API (GH-11922)

In the process of converting the date.fromtimestamp function to use
argument clinic in GH-8535, the C API for PyDate_FromTimestamp was
inadvertently changed to expect a timestamp object rather than an
argument tuple.

This PR fixes this backwards-incompatible change by adding a new wrapper
function for the C API function that unwraps the argument tuple and
passes it to the underlying function.

This PR also adds tests for both PyDate_FromTimestamp and
PyDateTime_FromTimestamp to prevent any further regressions.

1 files changed, 5 insertions, 0 deletions

diff --git a/Misc/NEWS.d/next/C API/2019-02-19-08-23-42.bpo-36025.tnwylQ.rst b/Misc/NEWS.d/next/C API/2019-02-19-08-23-42.bpo-36025.tnwylQ.rst
new file mode 100644
index 0000000..b00a33d
--- /dev/null
+++ b/Misc/NEWS.d/next/C API/2019-02-19-08-23-42.bpo-36025.tnwylQ.rst
@@ -0,0 +1,5 @@
+Fixed an accidental change to the datetime C API where the arguments to the
+:c:func:`PyDate_FromTimestamp` function were incorrectly interpreted as a
+single timestamp rather than an arguments tuple, which causes existing code to
+start raising :exc:`TypeError`. The backwards-incompatible change was only
+present in alpha releases of Python 3.8. Patch by Paul Ganssle.