1 files changed, 46 insertions, 0 deletions
diff --git a/coverage/debug.py b/coverage/debug.py
index 5b41bc40..8d36c1cd 100644
--- a/coverage/debug.py
+++ b/coverage/debug.py
@@ -1,6 +1,12 @@
+# Licensed under the Apache License: http://www.apache.org/licenses/LICENSE-2.0
+# For details: https://bitbucket.org/ned/coveragepy/src/default/NOTICE.txt
+
 """Control of and utilities for debugging."""
 
+import inspect
+import json
 import os
+import re
 
 
 # When debugging, it can be helpful to force some options, especially when
@@ -8,6 +14,9 @@ import os
 # This is a list of forced debugging options.
 FORCED_DEBUG = []
 
+# A hack for debugging testing in sub-processes.
+_TEST_NAME_FILE = ""    # "/tmp/covtest.txt"
+
 
 class DebugControl(object):
     """Control and output for debugging."""
@@ -66,3 +75,40 @@ def info_formatter(info):
                 prefix = ""
         else:
             yield "%*s: %s" % (label_len, label, data)
+
+
+def short_stack():                                          # pragma: debugging
+    """Return a string summarizing the call stack.
+
+    The string is multi-line, with one line per stack frame. Each line shows
+    the function name, the file name, and the line number:
+
+        ...
+        start_import_stop : /Users/ned/coverage/trunk/tests/coveragetest.py @95
+        import_local_file : /Users/ned/coverage/trunk/tests/coveragetest.py @81
+        import_local_file : /Users/ned/coverage/trunk/coverage/backward.py @159
+        ...
+
+    """
+    stack = inspect.stack()[:0:-1]
+    return "\n".join("%30s : %s @%d" % (t[3], t[1], t[2]) for t in stack)
+
+
+def dump_stack_frames():                                    # pragma: debugging
+    """Print a summary of the stack to stdout."""
+    print(short_stack())
+
+
+def pretty_data(data):
+    """Format data as JSON, but as nicely as possible.
+
+    Returns a string.
+
+    """
+    # Start with a basic JSON dump.
+    out = json.dumps(data, indent=4, sort_keys=True)
+    # But pairs of numbers shouldn't be split across lines...
+    out = re.sub(r"\[\s+(-?\d+),\s+(-?\d+)\s+]", r"[\1, \2]", out)
+    # Trailing spaces mess with tests, get rid of them.
+    out = re.sub(r"(?m)\s+$", "", out)
+    return out