1 files changed, 54 insertions, 0 deletions
diff --git a/python/helpers/coverage/debug.py b/python/helpers/coverage/debug.py
new file mode 100644
index 000000000000..104f3b1d0a43
--- /dev/null
+++ b/python/helpers/coverage/debug.py
@@ -0,0 +1,54 @@
+"""Control of and utilities for debugging."""
+
+import os
+
+
+# When debugging, it can be helpful to force some options, especially when
+# debugging the configuration mechanisms you usually use to control debugging!
+# This is a list of forced debugging options.
+FORCED_DEBUG = []
+
+
+class DebugControl(object):
+    """Control and output for debugging."""
+
+    def __init__(self, options, output):
+        """Configure the options and output file for debugging."""
+        self.options = options
+        self.output = output
+
+    def should(self, option):
+        """Decide whether to output debug information in category `option`."""
+        return (option in self.options or option in FORCED_DEBUG)
+
+    def write(self, msg):
+        """Write a line of debug output."""
+        if self.should('pid'):
+            msg = "pid %5d: %s" % (os.getpid(), msg)
+        self.output.write(msg+"\n")
+        self.output.flush()
+
+    def write_formatted_info(self, info):
+        """Write a sequence of (label,data) pairs nicely."""
+        for line in info_formatter(info):
+            self.write(" %s" % line)
+
+
+def info_formatter(info):
+    """Produce a sequence of formatted lines from info.
+
+    `info` is a sequence of pairs (label, data).  The produced lines are
+    nicely formatted, ready to print.
+
+    """
+    label_len = max([len(l) for l, _d in info])
+    for label, data in info:
+        if data == []:
+            data = "-none-"
+        if isinstance(data, (list, tuple)):
+            prefix = "%*s:" % (label_len, label)
+            for e in data:
+                yield "%*s %s" % (label_len+1, prefix, e)
+                prefix = ""
+        else:
+            yield "%*s: %s" % (label_len, label, data)