From f6027721b125af34862d1ba7ca5ba2205a09e1fe Mon Sep 17 00:00:00 2001
From: Gary Oberbrunner <garyo@oberbrunner.com>
Date: Tue, 1 Mar 2011 00:48:34 +0000
Subject: New debug option --debug=prepare to watch targets being prepared

---
 doc/man/scons.1                         | 12 ++++++++++++
 doc/user/troubleshoot.in                | 15 +++++++++++++++
 doc/user/troubleshoot.xml               | 15 +++++++++++++++
 src/CHANGES.txt                         |  4 ++++
 src/RELEASE.txt                         |  5 ++++-
 src/engine/SCons/Script/Main.py         |  2 ++
 src/engine/SCons/Script/SConsOptions.py |  2 +-
 src/engine/SCons/Taskmaster.py          |  8 ++++++++
 8 files changed, 61 insertions(+), 2 deletions(-)

diff --git a/doc/man/scons.1 b/doc/man/scons.1
index 5d3cfd9..3fa9e0c 100644
--- a/doc/man/scons.1
+++ b/doc/man/scons.1
@@ -664,6 +664,18 @@ Re-run SCons under the control of the
 Python debugger.
 
 .TP
+--debug=prepare
+Print a line each time any target (internal or external)
+is prepared for building.
+.B scons
+prints this for each target it considers, even if that
+target is up to date (see also --debug=explain).
+This can help debug problems with targets that aren't being
+built; it shows whether
+.B scons
+is at least considering them or not.
+
+.TP
 --debug=presub
 Print the raw command line used to build each target
 before the construction environment variables are substituted.
diff --git a/doc/user/troubleshoot.in b/doc/user/troubleshoot.in
index 392caf6..b0e8681 100644
--- a/doc/user/troubleshoot.in
+++ b/doc/user/troubleshoot.in
@@ -842,6 +842,21 @@
 
   </section>
 
+  <section>
+
+  <title>Watch &SCons; prepare targets for building: the &debug-prepare; Option</title>
+
+    <para>
+
+    Sometimes SCons doesn't build the target you want
+    and it's difficult to figure out why.  You can use
+    the <literal>--debug=prepare</literal> option
+    to see all the targets &SCons; is considering, whether
+    they are already up-to-date or not. The message is
+    printed before &SCons; decides whether to build the target.
+
+  </section>
+
   <!--
 
   <section>
diff --git a/doc/user/troubleshoot.xml b/doc/user/troubleshoot.xml
index 26e6996..586612a 100644
--- a/doc/user/troubleshoot.xml
+++ b/doc/user/troubleshoot.xml
@@ -1260,6 +1260,21 @@
 
   </section>
 
+  <section>
+
+  <title>Watch &SCons; prepare targets for building: the &debug-prepare; Option</title>
+
+    <para>
+
+    Sometimes SCons doesn't build the target you want
+    and it's difficult to figure out why.  You can use
+    the <literal>--debug=prepare</literal> option
+    to see all the targets &SCons; is considering, whether
+    they are already up-to-date or not. The message is
+    printed before &SCons; decides whether to build the target.
+
+  </section>
+
   <!--
 
   <section>
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):
-- 
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