A better way to prevent call stacks during multi-line output

2 files changed, 31 insertions, 18 deletions

diff --git a/coverage/control.py b/coverage/control.py
index 3464d66f..351992f2 100644
--- a/coverage/control.py
+++ b/coverage/control.py
@@ -366,18 +366,19 @@ class Coverage(object):
 
         # The user may want to debug things, show info if desired.
         wrote_any = False
-        if self.debug.should('config'):
-            config_info = sorted(self.config.__dict__.items())
-            self.debug.write_formatted_info("config", config_info)
-            wrote_any = True
-
-        if self.debug.should('sys'):
-            self.debug.write_formatted_info("sys", self.sys_info())
-            for plugin in self.plugins:
-                header = "sys: " + plugin._coverage_plugin_name
-                info = plugin.sys_info()
-                self.debug.write_formatted_info(header, info)
-            wrote_any = True
+        with self.debug.without_callers():
+            if self.debug.should('config'):
+                config_info = sorted(self.config.__dict__.items())
+                self.debug.write_formatted_info("config", config_info)
+                wrote_any = True
+
+            if self.debug.should('sys'):
+                self.debug.write_formatted_info("sys", self.sys_info())
+                for plugin in self.plugins:
+                    header = "sys: " + plugin._coverage_plugin_name
+                    info = plugin.sys_info()
+                    self.debug.write_formatted_info(header, info)
+                wrote_any = True
 
         if wrote_any:
             self.debug.write_formatted_info("end", ())
diff --git a/coverage/debug.py b/coverage/debug.py
index 957a6fe6..dff8beba 100644
--- a/coverage/debug.py
+++ b/coverage/debug.py
@@ -3,6 +3,7 @@
 
 """Control of and utilities for debugging."""
 
+import contextlib
 import inspect
 import os
 import re
@@ -29,26 +30,37 @@ class DebugControl(object):
         """Configure the options and output file for debugging."""
         self.options = options
         self.output = output
+        self.suppress_callers = False
 
     def __repr__(self):
         return "<DebugControl options=%r output=%r>" % (self.options, self.output)
 
     def should(self, option):
         """Decide whether to output debug information in category `option`."""
+        if option == "callers" and self.suppress_callers:
+            return False
         return (option in self.options or option in FORCED_DEBUG)
 
-    def write(self, msg, callers=True):
+    @contextlib.contextmanager
+    def without_callers(self):
+        """A context manager to prevent call stacks from being logged."""
+        old = self.suppress_callers
+        self.suppress_callers = True
+        try:
+            yield
+        finally:
+            self.suppress_callers = old
+
+    def write(self, msg):
         """Write a line of debug output.
 
-        `msg` is the line to write. A newline will be appended.  If `callers`
-        is true, and the user has requested it, the call stack will be written
-        also.
+        `msg` is the line to write. A newline will be appended.
 
         """
         if self.should('pid'):
             msg = "pid %5d: %s" % (os.getpid(), msg)
         self.output.write(msg+"\n")
-        if callers and self.should('callers'):
+        if self.should('callers'):
             dump_stack_frames(out=self.output, skip=1)
         self.output.flush()
 
@@ -56,7 +68,7 @@ class DebugControl(object):
         """Write a sequence of (label,data) pairs nicely."""
         self.write(info_header(header))
         for line in info_formatter(info):
-            self.write(" %s" % line, callers=False)
+            self.write(" %s" % line)
 
 
 def info_header(label):