Correctly fix bug #2903, failure to rebuild when linker options change.

The failure to rebuild when linker options change was introduced in
abded0675444, "Add library version support to Shared Lib builder",
between 2.2.0 and 2.3.0.

Turning ShlinkAction into a FunctionAction instead of a CommandAction
made it stop depending on $SHLINKCOM.  Normally, a CommandAction calls
get_presig (Action.py:815) which removes $( ... $) and uses the rest
of that string (recursively fully substituted) as the contents to
hash.

FunctionActions only look at the body of the function, so that removed
the dependency on $SHLINKCOM altogether.  Adding it back in the
varlist does this (Action.py:443):
        for v in vl:
            result.append(env.subst('${'+v+'}'))
so it deep-substitutes the whole thing, including all the $( ... $)
parts.  (All varlist vars do this, not just in FunctionActions.)

What we really want is to depend on the value of env['SHLINKCOM']
in the way CommandActions do, i.e. without the $( ... $)
parts, definitely not the fully substituted version of it.

I'm pretty sure the ignored $(...$) parts should not ever be
included in the signature, so this change updates the varlist handling
code to work the way CommandActions always have.

This change also renames the test files to use the correct bug
number and updates the test.

8 files changed, 36 insertions, 8 deletions

diff --git a/src/engine/SCons/Action.py b/src/engine/SCons/Action.py
index c1eef756..543c37c8 100644
--- a/src/engine/SCons/Action.py
+++ b/src/engine/SCons/Action.py
@@ -439,7 +439,8 @@ class ActionBase(object):
         vl = self.get_varlist(target, source, env)
         if is_String(vl): vl = (vl,)
         for v in vl:
-            result.append(env.subst('${'+v+'}'))
+            # do the subst this way to ignore $(...$) parts:
+            result.append(env.subst_target_source('${'+v+'}', SCons.Subst.SUBST_SIG, target, source))
         return ''.join(result)
 
     def __add__(self, other):
diff --git a/src/engine/SCons/Tool/__init__.py b/src/engine/SCons/Tool/__init__.py
index 7477f752..c09f8e48 100644
--- a/src/engine/SCons/Tool/__init__.py
+++ b/src/engine/SCons/Tool/__init__.py
@@ -364,8 +364,12 @@ symlinks for the platform we are on"""
                 print "VerShLib: made sym link of %s -> %s" % (linkname, lib_ver)
     return result
 
-# Fix http://scons.tigris.org/issues/show_bug.cgi?id=2903 : 
-# varlist=['$SHLINKCOM']: ensure we still depend on SCons.Defaults.ShLinkAction command line which is $SHLINKCOM 
+# Fix http://scons.tigris.org/issues/show_bug.cgi?id=2903 :
+# Ensure we still depend on SCons.Defaults.ShLinkAction command line which is $SHLINKCOM.
+# This was tricky because we don't want changing LIBPATH to cause a rebuild, but
+# changing other link args should.  LIBPATH has $( ... $) around it but until this
+# fix, when the varlist was added to the build sig those ignored parts weren't getting
+# ignored.
 ShLibAction = SCons.Action.Action(VersionedSharedLibrary, None, varlist=['SHLINKCOM'])
 
 def createSharedLibBuilder(env):
diff --git a/test/Libs/SharedLibrary-update-deps.py b/test/Libs/SharedLibrary-update-deps.py
index 24c5262d..e8ec2abb 100644
--- a/test/Libs/SharedLibrary-update-deps.py
+++ b/test/Libs/SharedLibrary-update-deps.py
@@ -26,18 +26,20 @@ __revision__ = "__FILE__ __REVISION__ __DATE__ __DEVELOPER__"
 
 """
 Test that SharedLibrary() updates when a different lib is linked, even if it has the same md5.
-This is Tigris bug #2909.
+This is Tigris bug #2903.
 """
 
+import sys
 import os.path
 import TestSCons
 
 test = TestSCons.TestSCons()
 
-test.dir_fixture( "bug2909" )
+test.dir_fixture( "bug2903" )
 
 # Build the sub-libs (don't care about details of this)
 test.run(arguments='-f SConstruct-libs')
+
 # This should build the main lib, using libfoo.so
 test.run(arguments='libname=foo')
 # This should rebuild the main lib, using libbar.so;
@@ -48,6 +50,17 @@ test.must_not_contain_any_line(test.stdout(), ["is up to date"])
 test.run(arguments='libname=foo')
 test.must_not_contain_any_line(test.stdout(), ["is up to date"])
 
+# Now try changing the link command line (in an innocuous way); should rebuild.
+if sys.platform == 'win32':
+    extraflags='shlinkflags=/DEBUG'
+else:
+    extraflags='shlinkflags=-g'
+
+test.run(arguments=['libname=foo', extraflags])
+test.must_not_contain_any_line(test.stdout(), ["is up to date"])
+test.run(arguments=['libname=foo', extraflags])
+test.must_contain_all_lines(test.stdout(), ["is up to date"])
+
 test.pass_test()
 
 # Local Variables:
diff --git a/test/Libs/bug2903/SConstruct b/test/Libs/bug2903/SConstruct
new file mode 100644
index 00000000..f7b66a84
--- /dev/null
+++ b/test/Libs/bug2903/SConstruct
@@ -0,0 +1,13 @@
+# SConstruct for testing but #2903.
+# The test changes the lib name to make sure it rebuilds
+# when the name changes, even if the content of the lib is the same.
+# Also, the test passes in extra shlinkflags to ensure things rebuild
+# when other linker options change, and not when they don't.
+# (This doesn't specifically test LIBPATH, but there's a test for
+# that already.)
+env=Environment()
+libname=ARGUMENTS.get('libname', 'foo')
+env['SHLINKCOM'] = env['SHLINKCOM'] + ' $EXTRA_SHLINKFLAGS'
+shlinkflags=ARGUMENTS.get('shlinkflags', '')
+env.SharedLibrary('myshared', ['main.c'],
+                  LIBS=[libname], LIBPATH='.', EXTRA_SHLINKFLAGS=shlinkflags)
diff --git a/test/Libs/bug2909/SConstruct-libs b/test/Libs/bug2903/SConstruct-libs
index 3f59f9c5..3f59f9c5 100644
--- a/test/Libs/bug2909/SConstruct-libs
+++ b/test/Libs/bug2903/SConstruct-libs
diff --git a/test/Libs/bug2909/lib.c b/test/Libs/bug2903/lib.c
index 048f715b..048f715b 100644
--- a/test/Libs/bug2909/lib.c
+++ b/test/Libs/bug2903/lib.c
diff --git a/test/Libs/bug2909/main.c b/test/Libs/bug2903/main.c
index 3fe7d491..3fe7d491 100644
--- a/test/Libs/bug2909/main.c
+++ b/test/Libs/bug2903/main.c
diff --git a/test/Libs/bug2909/SConstruct b/test/Libs/bug2909/SConstruct
deleted file mode 100644
index 2c5440b9..00000000
--- a/test/Libs/bug2909/SConstruct
+++ /dev/null
@@ -1,3 +0,0 @@
-env=Environment()
-libname=ARGUMENTS.get('libname', 'foo')
-env.SharedLibrary('myshared', ['main.c'], LIBS=[libname], LIBPATH='.')
\ No newline at end of file