Read the data file from the COVERAGE_FILE environment variable.

--HG--
branch : config

2 files changed, 25 insertions, 1 deletions

diff --git a/coverage/control.py b/coverage/control.py
index 77678543..eb134450 100644
--- a/coverage/control.py
+++ b/coverage/control.py
@@ -60,13 +60,23 @@ class coverage(object):
         """
         from coverage import __version__
 
-        # Build our configuration from a number of sources.
+        # Build our configuration from a number of sources:
+        # 1: defaults:
         self.config = CoverageConfig()
+        
+        # 2: from the coveragerc file:
         if config_file:
             if config_file is True:
                 config_file = ".coveragerc"
             self.config.from_file(config_file)
+        
+        # 3: from environment variables:
         self.config.from_environment('COVERAGE_OPTIONS')
+        env_data_file = os.environ.get('COVERAGE_FILE')
+        if env_data_file:
+            self.config.data_file = env_data_file
+        
+        # 4: from constructor arguments:
         self.config.from_args(
             data_file=data_file, cover_pylib=cover_pylib, timid=timid,
             branch=branch
diff --git a/test/test_config.py b/test/test_config.py
index 06d43d31..a1abf51b 100644
--- a/test/test_config.py
+++ b/test/test_config.py
@@ -73,3 +73,17 @@ class ConfigTest(CoverageTest):
         self.assertFalse(cov.config.timid)
         self.assertFalse(cov.config.branch)
         self.assertEqual(cov.config.data_file, ".mycov")
+
+    def test_data_file_from_environment(self):
+        # There's an environment variable for the data_file.
+        self.make_file(".coveragerc", """\
+            [run]
+            timid = True
+            data_file = weirdo.file
+            """)
+        self.set_environ("COVERAGE_FILE", "fromenv.dat")
+        cov = coverage.coverage()
+        self.assertEqual(cov.config.data_file, "fromenv.dat")
+        # But the constructor args override the env var.
+        cov = coverage.coverage(data_file="fromarg.dat")
+        self.assertEqual(cov.config.data_file, "fromarg.dat")