Fix the return value of the base Node.get_prevsiginfo(). (Gary Oberbrunner)

3 files changed, 17 insertions, 5 deletions

diff --git a/src/engine/SCons/Node/NodeTests.py b/src/engine/SCons/Node/NodeTests.py
index 103cfae..2d6e0bc 100644
--- a/src/engine/SCons/Node/NodeTests.py
+++ b/src/engine/SCons/Node/NodeTests.py
@@ -971,6 +971,13 @@ class NodeTestCase(unittest.TestCase):
 
         assert n.get_subst_proxy() == n, n.get_subst_proxy()
 
+    def test_get_prevsiginfo(self):
+        """Test the base Node get_prevsiginfo() method"""
+        n = SCons.Node.Node()
+        siginfo = n.get_prevsiginfo()
+        assert siginfo == (None, None, None), siginfo
+
+
 
 if __name__ == "__main__":
     suite = unittest.makeSuite(NodeTestCase, 'test_')
diff --git a/src/engine/SCons/Node/__init__.py b/src/engine/SCons/Node/__init__.py
index 6947c93..1a80d5a 100644
--- a/src/engine/SCons/Node/__init__.py
+++ b/src/engine/SCons/Node/__init__.py
@@ -513,7 +513,7 @@ class Node:
     def get_prevsiginfo(self):
         """Fetch the previous signature information from the
         .sconsign entry."""
-        return None
+        return SCons.Sig._SConsign.null_siginfo
 
     def get_timestamp(self):
         return 0
diff --git a/src/engine/SCons/Sig/__init__.py b/src/engine/SCons/Sig/__init__.py
index 36145cb..b4b70b4 100644
--- a/src/engine/SCons/Sig/__init__.py
+++ b/src/engine/SCons/Sig/__init__.py
@@ -103,6 +103,11 @@ class _SConsign:
         global sig_files
         sig_files.append(self)
 
+    # A null .sconsign entry.  We define this here so that it will
+    # be easy to keep this in sync if/whenever we change the type of
+    # information returned by the get() method, below.
+    null_siginfo = (None, None, None)
+
     def get(self, filename):
         """
         Get the .sconsign entry for a file
@@ -321,15 +326,15 @@ class Calculator:
             return csig
         
         if self.max_drift >= 0:
-            info = node.get_prevsiginfo()
+            oldtime, oldbsig, oldcsig = node.get_prevsiginfo()
         else:
-            info = None
+            oldtime, oldbsig, oldcsig = _SConsign.null_siginfo
 
         mtime = node.get_timestamp()
 
-        if (info and info[0] and info[2] and info[0] == mtime):
+        if (oldtime and oldcsig and oldtime == mtime):
             # use the signature stored in the .sconsign file
-            csig = info[2]
+            csig = oldcsig
             # Set the csig here so it doesn't get recalculated unnecessarily
             # and so it's set when the .sconsign file gets written
             cache.set_csig(csig)