[mac] Add compatibility with old macOS versions (#733)

* Add compatibility with old macOS versions

* Define symbols only for older versions

And not for older or equal, since the equal version is when the symbol
was introduced.

* Ensure version macros are available

* Update changelog

changelog.rst

@@ -9,7 +9,8 @@ Changelog
 202x-xx-xx • `full history <https://github.com/gorakhargosh/watchdog/compare/v1.0.1...master>`__
 
 - [mac] Fix missing ``event_id`` attribute in ``fsevents`` (`#721 <https://github.com/gorakhargosh/watchdog/pull/721>`_)
-- Thanks to our beloved contributors: @SamSchott
+- [mac] Add compatibility with old macOS versions (`#733` <https://github.com/gorakhargosh/watchdog/pull/733>`_)
+- Thanks to our beloved contributors: @SamSchott, @CCP-Aporia
 
 
 1.0.1

src/watchdog_fsevents.c

@@ -20,12 +20,38 @@
 
 
 #include <Python.h>
+#include <Availability.h>
 #include <CoreFoundation/CoreFoundation.h>
 #include <CoreServices/CoreServices.h>
 #include <stdlib.h>
 #include <signal.h>
 
 
+/* Compatibility; since fsevents won't set these on earlier macOS versions the properties will always be False */
+#if MAC_OS_X_VERSION_MAX_ALLOWED < MAC_OS_X_VERSION_10_7
+#error Watchdog module requires at least Mac OS X 10.7
+#endif
+#ifndef MAC_OS_X_VERSION_10_9
+#define MAC_OS_X_VERSION_10_9         1090
+#endif
+#ifndef MAC_OS_X_VERSION_10_10
+#define MAC_OS_X_VERSION_10_10      101000
+#endif
+#ifndef MAC_OS_X_VERSION_10_13
+#define MAC_OS_X_VERSION_10_13      101300
+#endif
+#if MAC_OS_X_VERSION_MAX_ALLOWED < MAC_OS_X_VERSION_10_9
+#define kFSEventStreamEventFlagOwnEvent 0x00080000
+#endif
+#if MAC_OS_X_VERSION_MAX_ALLOWED < MAC_OS_X_VERSION_10_10
+#define kFSEventStreamEventFlagItemIsHardlink 0x00100000
+#define kFSEventStreamEventFlagItemIsLastHardlink 0x00200000
+#endif
+#if MAC_OS_X_VERSION_MAX_ALLOWED < MAC_OS_X_VERSION_10_13
+#define kFSEventStreamEventFlagItemCloned 0x00400000
+#endif
+
+
 /* Convenience macros to make code more readable. */
 #define G_NOT(o)                        !o
 #define G_IS_NULL(o)                    o == NULL