Set TaskBase.keep_last_cmd to keep the last command executed

ChangeLog

@@ -4,6 +4,7 @@ NEW IN WAF 1.9.2
 * Force qt5 static library detection with 'QT5_XCOMPILE=1 QT5_FORCE_STATIC=1 waf configure' #1588
 * Remove the non-BSD code from the Waf archive file
 * Update a few extensions: xcode, pytest, msvcdeps, cppcheck, win32_opts, codelite
+* Store Task.last_cmd selectively, so that extensions can use them (clang_compilation_database)
 
 NEW IN WAF 1.9.1
 ----------------

waflib/Task.py

@@ -69,11 +69,6 @@ def f(tsk):
 	return tsk.exec_command(lst, cwd=cwdx, env=env.env or None)
 '''
 
-KEEP_LAST_CMD = False
-"""
-Whether the last executed command on task objects should be removed
-"""
-
 classes = {}
 """
 The metaclass :py:class:`waflib.Task.store_task_type` stores all class tasks
@@ -146,6 +141,11 @@ class TaskBase(evil):
 	hcode = ''
 	"""String representing an additional hash for the class representation"""
 
+	keep_last_cmd = False
+	"""Whether to keep the last command executed on the instance after execution.
+	This may be useful for certain extensions but it can a lot of memory.
+	"""
+
 	__slots__ = ('hasrun', 'generator')
 
 	def __init__(self, *k, **kw):
@@ -690,8 +690,7 @@ class Task(TaskBase):
 				raise Errors.WafError(self.err_msg)
 			bld.node_sigs[node] = self.uid() # make sure this task produced the files in question
 		bld.task_sigs[self.uid()] = self.signature()
-		global KEEP_LAST_CMD
-		if not KEEP_LAST_CMD:
+		if not self.keep_last_cmd:
 			try:
 				del self.last_cmd
 			except AttributeError:

waflib/extras/clang_compilation_database.py

@@ -17,7 +17,7 @@ Usage:
 import sys, os, json, shlex, pipes
 from waflib import Logs, TaskGen, Task
 
-Task.KEEP_LAST_CMD = True
+Task.TaskBase.keep_last_cmd = True
 
 if sys.hexversion >= 0x3030000:
 	quote = shlex.quote