Make sure check_include isn't called more than once per file.

2 files changed, 7 insertions, 1 deletions

diff --git a/coverage/control.py b/coverage/control.py
index cb614d56..7e338625 100644
--- a/coverage/control.py
+++ b/coverage/control.py
@@ -936,6 +936,8 @@ class FileDisposition(object):
         """Produce a debugging message explaining the outcome."""
         if self.trace:
             msg = "Tracing %r" % (self.original_filename,)
+            if self.file_tracer:
+                msg += ": will be traced by %r" % self.file_tracer
         else:
             msg = "Not tracing %r: %s" % (self.original_filename, self.reason)
         return msg
diff --git a/coverage/pytracer.py b/coverage/pytracer.py
index 98b52028..16a51c2b 100644
--- a/coverage/pytracer.py
+++ b/coverage/pytracer.py
@@ -87,7 +87,11 @@ class PyTracer(object):
                 if disp.file_tracer and disp.has_dynamic_filename:
                     tracename = disp.file_tracer.dynamic_source_filename(tracename, frame)
                     if tracename:
-                        if not self.check_include(tracename, frame):
+                        included = self.should_trace_cache.get(tracename)
+                        if included is None:
+                            included = self.check_include(tracename, frame)
+                            self.should_trace_cache[tracename] = included
+                        if not included:
                             tracename = None
             else:
                 tracename = None