1 files changed, 142 insertions, 1 deletions
diff --git a/coverage/plugin_support.py b/coverage/plugin_support.py
index 9ab7954..8bdc721 100644
--- a/coverage/plugin_support.py
+++ b/coverage/plugin_support.py
@@ -3,6 +3,7 @@
 import sys
 
 from coverage.misc import CoverageException
+from coverage.plugin import CoveragePlugin, FileTracer, FileReporter
 
 
 class Plugins(object):
@@ -13,7 +14,7 @@ class Plugins(object):
         self.names = {}
 
     @classmethod
-    def load_plugins(cls, modules, config):
+    def load_plugins(cls, modules, config, debug=None):
         """Load plugins from `modules`.
 
         Returns a list of loaded and configured plugins.
@@ -31,6 +32,10 @@ class Plugins(object):
 
             options = config.get_plugin_options(module)
             plugin = plugin_class(options)
+            if debug and debug.should('plugin'):
+                debug.write("Loaded plugin %r: %r" % (module, plugin))
+                labelled = LabelledDebug("plugin %r" % (module,), debug)
+                plugin = DebugPluginWrapper(plugin, labelled)
             plugin._coverage_plugin_name = module
             plugin._coverage_enabled = True
             plugins.order.append(plugin)
@@ -49,3 +54,139 @@ class Plugins(object):
     def get(self, plugin_name):
         """Return a plugin by name."""
         return self.names[plugin_name]
+
+
+class LabelledDebug(object):
+    """A Debug writer, but with labels for prepending to the messages."""
+
+    def __init__(self, label, debug, prev_labels=()):
+        self.labels = list(prev_labels) + [label]
+        self.debug = debug
+
+    def add_label(self, label):
+        """Add a label to the writer, and return a new `LabelledDebug`."""
+        return LabelledDebug(label, self.debug, self.labels)
+
+    def write(self, message):
+        """Write `message`, but with the labels prepended."""
+        self.debug.write("%s: %s" % (", ".join(self.labels), message))
+
+
+class DebugPluginWrapper(CoveragePlugin):
+    """Wrap a plugin, and use debug to report on what it's doing."""
+
+    def __init__(self, plugin, debug):
+        super(DebugPluginWrapper, self).__init__()
+        self.plugin = plugin
+        self.debug = debug
+
+    def file_tracer(self, filename):
+        tracer = self.plugin.file_tracer(filename)
+        self.debug.write("file_tracer(%r) --> %r" % (filename, tracer))
+        if tracer:
+            debug = self.debug.add_label("file %r" % (filename,))
+            tracer = DebugFileTracerWrapper(tracer, debug)
+        return tracer
+
+    def file_reporter(self, filename):
+        reporter = self.plugin.file_reporter(filename)
+        self.debug.write("file_reporter(%r) --> %r" % (filename, reporter))
+        if reporter:
+            debug = self.debug.add_label("file %r" % (filename,))
+            reporter = DebugFileReporterWrapper(filename, reporter, debug)
+        return reporter
+
+    def sys_info(self):
+        return self.plugin.sys_info()
+
+
+class DebugFileTracerWrapper(FileTracer):
+    """A debugging `FileTracer`."""
+
+    def __init__(self, tracer, debug):
+        self.tracer = tracer
+        self.debug = debug
+
+    def source_filename(self):
+        sfilename = self.tracer.source_filename()
+        self.debug.write("source_filename() --> %r" % (sfilename,))
+        return sfilename
+
+    def has_dynamic_source_filename(self):
+        has = self.tracer.has_dynamic_source_filename()
+        self.debug.write("has_dynamic_source_filename() --> %r" % (has,))
+        return has
+
+    def dynamic_source_filename(self, filename, frame):
+        dyn = self.tracer.dynamic_source_filename(filename, frame)
+        self.debug.write("dynamic_source_filename(%r, frame) --> %r" % (filename, dyn))
+        return dyn
+
+    def line_number_range(self, frame):
+        pair = self.tracer.line_number_range(frame)
+        self.debug.write("line_number_range(frame) --> %r" % (pair,))
+        return pair
+
+
+class DebugFileReporterWrapper(FileReporter):
+    """A debugging `FileReporter`."""
+
+    def __init__(self, filename, reporter, debug):
+        super(DebugFileReporterWrapper, self).__init__(filename)
+        self.reporter = reporter
+        self.debug = debug
+
+    def relative_filename(self):
+        ret = self.reporter.relative_filename()
+        self.debug.write("relative_filename() --> %r" % (ret,))
+        return ret
+
+    def statements(self):
+        ret = self.reporter.statements()
+        self.debug.write("statements() --> %r" % (ret,))
+        return ret
+
+    def excluded_statements(self):
+        ret = self.reporter.excluded_statements()
+        self.debug.write("excluded_statements() --> %r" % (ret,))
+        return ret
+
+    def translate_lines(self, lines):
+        ret = self.reporter.translate_lines(lines)
+        self.debug.write("translate_lines(%r) --> %r" % (lines, ret))
+        return ret
+
+    def translate_arcs(self, arcs):
+        ret = self.reporter.translate_arcs(arcs)
+        self.debug.write("translate_arcs(%r) --> %r" % (arcs, ret))
+        return ret
+
+    def no_branch_lines(self):
+        ret = self.reporter.no_branch_lines()
+        self.debug.write("no_branch_lines() --> %r" % (ret,))
+        return ret
+
+    def exit_counts(self):
+        ret = self.reporter.exit_counts()
+        self.debug.write("exit_counts() --> %r" % (ret,))
+        return ret
+
+    def arcs(self):
+        ret = self.reporter.arcs()
+        self.debug.write("arcs() --> %r" % (ret,))
+        return ret
+
+    def source(self):
+        ret = self.reporter.source()
+        self.debug.write("source() --> %d chars" % (len(ret),))
+        return ret
+
+    def source_token_lines(self):
+        ret = list(self.reporter.source_token_lines())
+        self.debug.write("source_token_lines() --> %d tokens" % (len(ret),))
+        return ret
+
+    def should_be_python(self):
+        ret = self.reporter.should_be_python()
+        self.debug.write("should_be_python() --> %r" % (ret,))
+        return ret