When reporting, don't fall over if there's no data to report on. Fixes issue #37.

3 files changed, 14 insertions, 6 deletions

diff --git a/coverage/control.py b/coverage/control.py
index e041cde7..4bcb4ed4 100644
--- a/coverage/control.py
+++ b/coverage/control.py
@@ -304,8 +304,12 @@ class coverage(object):
         """
         if outfile:
             outfile = open(outfile, "w")
-        reporter = XmlReporter(self, ignore_errors)
-        reporter.report(morfs, omit_prefixes=omit_prefixes, outfile=outfile)
+        try:
+            reporter = XmlReporter(self, ignore_errors)
+            reporter.report(
+                morfs, omit_prefixes=omit_prefixes, outfile=outfile)
+        finally:
+            outfile.close()
 
     def sysinfo(self):
         """Return a list of key,value pairs showing internal information."""
diff --git a/coverage/report.py b/coverage/report.py
index 7f3e3e02..c2215521 100644
--- a/coverage/report.py
+++ b/coverage/report.py
@@ -2,7 +2,7 @@
 
 import os
 from coverage.codeunit import code_unit_factory
-from coverage.misc import NoSource
+from coverage.misc import CoverageException, NoSource
 
 class Reporter(object):
     """A base class for all reporters."""
@@ -45,6 +45,9 @@ class Reporter(object):
         """
         self.find_code_units(morfs, omit_prefixes)
 
+        if not self.code_units:
+            raise CoverageException("No data to report.")
+
         self.directory = directory
         if self.directory and not os.path.exists(self.directory):
             os.makedirs(self.directory)
diff --git a/coverage/xmlreport.py b/coverage/xmlreport.py
index 0fe43712..2e31d9e9 100644
--- a/coverage/xmlreport.py
+++ b/coverage/xmlreport.py
@@ -30,7 +30,6 @@ class XmlReporter(Reporter):
         """
         # Initial setup.
         outfile = outfile or sys.stdout
-        self.find_code_units(morfs, omit_prefixes)
 
         # Create the DOM that will store the data.
         impl = xml.dom.minidom.getDOMImplementation()
@@ -39,8 +38,9 @@ class XmlReporter(Reporter):
             "http://cobertura.sourceforge.net/xml/coverage-03.dtd"
             )
         self.xml_out = impl.createDocument(None, "coverage", docType)
+        
+        # Write header stuff.
         xcoverage = self.xml_out.documentElement
-
         xcoverage.setAttribute("version", __version__)
         xcoverage.setAttribute("timestamp", str(int(time.time()*1000)))
         xcoverage.appendChild(self.xml_out.createComment(
@@ -48,8 +48,9 @@ class XmlReporter(Reporter):
             ))
         xpackages = self.xml_out.createElement("packages")
         xcoverage.appendChild(xpackages)
-        self.packages = {}
 
+        # Call xml_file for each file in the data.
+        self.packages = {}
         self.report_files(self.xml_file, morfs, omit_prefixes=omit_prefixes)
 
         lnum_tot, lhits_tot = 0, 0