New debug option --debug=prepare to watch targets being prepared

5 files changed, 19 insertions, 2 deletions

diff --git a/src/CHANGES.txt b/src/CHANGES.txt
index f49c9af..31fa245 100644
--- a/src/CHANGES.txt
+++ b/src/CHANGES.txt
@@ -10,6 +10,10 @@ RELEASE 2.1.0.alpha.yyyymmdd - NEW DATE WILL BE INSERTED HERE
   From Gary Oberbrunner:
     - Adding None to an Action no longer fails (just returns original action)
 
+  From Gary Oberbrunner:
+    - New --debug=prepare option to show each target as it's being
+      prepared, whether or not anything needs to be done for it.
+
   From David Garcia Garzon:
     - Fix Delete to be able to delete broken symlinks and dir
       symlinks.
diff --git a/src/RELEASE.txt b/src/RELEASE.txt
index 4c0017f..f9d550e 100644
--- a/src/RELEASE.txt
+++ b/src/RELEASE.txt
@@ -49,7 +49,7 @@
     - List modifications to existing features, where the previous behavior
       wouldn't actually be considered a bug
 
-    - Add initial support for VS/VC 2001
+    - Add initial support for VS/VC 2010
 
   FIXES
 
@@ -82,6 +82,9 @@
     - TeX command strings now work on Windows when the new dir is
       on a different drive letter.
     - DMD version 2 is supported (using the phobos2 library)
+    - New --debug=prepare option shows each target as it's prepared
+      for building; can help when you don't know why a target isn't
+      being built.
 
     - List improvements that wouldn't be visible to the user in the
       documentation:  performance improvements (describe the circumstances
diff --git a/src/engine/SCons/Script/Main.py b/src/engine/SCons/Script/Main.py
index e0600bd..0513e41 100644
--- a/src/engine/SCons/Script/Main.py
+++ b/src/engine/SCons/Script/Main.py
@@ -654,6 +654,8 @@ def _set_debug_values(options):
         print_time = 1
     if "tree" in debug_values:
         options.tree_printers.append(TreePrinter())
+    if "prepare" in debug_values:
+        SCons.Taskmaster.print_prepare = 1
 
 def _create_path(plist):
     path = '.'
diff --git a/src/engine/SCons/Script/SConsOptions.py b/src/engine/SCons/Script/SConsOptions.py
index ceb6006..fc5f08d 100644
--- a/src/engine/SCons/Script/SConsOptions.py
+++ b/src/engine/SCons/Script/SConsOptions.py
@@ -598,7 +598,7 @@ def Parser(version):
 
     debug_options = ["count", "explain", "findlibs",
                      "includes", "memoizer", "memory", "objects",
-                     "pdb", "presub", "stacktrace",
+                     "pdb", "prepare", "presub", "stacktrace",
                      "time"] + list(deprecated_debug_options.keys())
 
     def opt_debug(option, opt, value, parser,
diff --git a/src/engine/SCons/Taskmaster.py b/src/engine/SCons/Taskmaster.py
index 8cf5595..58a8d90 100644
--- a/src/engine/SCons/Taskmaster.py
+++ b/src/engine/SCons/Taskmaster.py
@@ -66,6 +66,7 @@ NODE_UP_TO_DATE = SCons.Node.up_to_date
 NODE_EXECUTED = SCons.Node.executed
 NODE_FAILED = SCons.Node.failed
 
+print_prepare = 0               # set by option --debug=prepare
 
 # A subsystem for recording stats about how different Nodes are handled by
 # the main Taskmaster loop.  There's no external control here (no need for
@@ -161,6 +162,7 @@ class Task(object):
         unlink underlying files and make all necessary directories before
         the Action is actually called to build the targets.
         """
+        global print_prepare
         T = self.tm.trace
         if T: T.write(self.trace_message(u'Task.prepare()', self.node))
 
@@ -186,8 +188,14 @@ class Task(object):
         executor = self.targets[0].get_executor()
         executor.prepare()
         for t in executor.get_action_targets():
+            if print_prepare:
+                print "Preparing target %s..."%t
+                for s in t.side_effects:
+                    print "...with side-effect %s..."%s
             t.prepare()
             for s in t.side_effects:
+                if print_prepare:
+                    print "...Preparing side-effect %s..."%s
                 s.prepare()
 
     def get_target(self):