Fix 2281 aliases ignore pre post add actions

CHANGES.txt

@@ -96,6 +96,8 @@ RELEASE  VERSION/DATE TO BE FILLED IN LATER
       specified `local_only`, but the code and tests were using `keep_local`. The functionality
       more closely matches local only.  NOTE: It doesn't seem like any code in the wild was using
       local_only as we'd not received any reports of such until PR #4606 from hedger.
+    - Fix Issue #2281, AddPreAction() & AddPostAction() were being ignored if no action
+      was specified when the Alias was initially created.
 
   From Alex James:
     - On Darwin, PermissionErrors are now handled while trying to access

RELEASE.txt

@@ -176,6 +176,8 @@ FIXES
   more closely matches local only.  NOTE: It doesn't seem like any code in the wild was using
   local_only as we'd not received any reports of such until PR #4606 from hedger.
 
+- Fix Issue #2281, AddPreAction() & AddPostAction() were being ignored if no action
+  was specified when the Alias was initially created.
 
 IMPROVEMENTS
 ------------

SCons/Node/Alias.py

@@ -104,9 +104,15 @@ def sconsign(self) -> None:
     #
     #
 
-    def build(self) -> None:
+    def build(self, **kw) -> None:
         """A "builder" for aliases."""
-        pass
+        if len(self.executor.post_actions) + len(self.executor.pre_actions) > 0:
+            # Only actually call Node's build() if there are any
+            # pre or post actions.
+            # Alias nodes will get 1 action and Alias.build()
+            # This fixes GH Issue #2281
+            return self.really_build(**kw)
+
 
     def convert(self) -> None:
         try: del self.builder

test/Alias/action.py

@@ -69,6 +69,19 @@ def bar(target, source, env):
 env.Alias('build-add3', f6)
 env.Alias('build-add3', action=foo)
 env.Alias('build-add3', action=bar)
+
+
+f7 = env.Cat('f7.out', 'f6.in')
+def build_it(target, source, env):
+    print("build_it: Goodbye")
+    return 0
+
+def string_it(target, source, env):
+    return("string it: Goodbye")
+
+s = Action(build_it, string_it)
+env.Alias('add_post_action', f7)
+env.AddPostAction('add_post_action', s)
 """)
 
 test.write('f1.in', "f1.in 1\n")
@@ -133,6 +146,9 @@ def bar(target, source, env):
 test.must_match('foo', "foo(['build-add3'], ['f6.out'])\n")
 test.must_match('bar', "bar(['build-add3'], ['f6.out'])\n")
 
+test.run(arguments = 'add_post_action')
+test.must_contain_all(test.stdout(), 'string it: Goodbye')
+
 test.pass_test()
 
 # Local Variables: