coverage run: add an output option (-o)

Similar to coverage report/xml/json, coverage run now has a -o option to
configure the file the SQLite coverage data will be stored in. The
default is still ".coverage", as previously.

Since data_file now needs to be specified in cmdline.py,
_DEFAULT_DATAFILE needs to be exposed (to avoid hacks like constructing
the argument dictionary manually). Rename it to non-undescore and create
an alias for it under the previous name (just in case someone used it
anyway).

Author: nbfalcon

coverage/cmdline.py

@@ -18,6 +18,7 @@
 from coverage import env
 from coverage.collector import CTracer
 from coverage.config import CoverageConfig
+from coverage.control import DEFAULT_DATAFILE
 from coverage.data import combinable_files, debug_data_file
 from coverage.debug import info_formatter, info_header, short_stack
 from coverage.exceptions import _BaseCoverageException, _ExceptionDuringRun, NoSource
@@ -123,6 +124,11 @@ class Opts:
         metavar="OUTFILE",
         help="Write the JSON report to this file. Defaults to 'coverage.json'",
     )
+    output_coverage = optparse.make_option(
+        '-o', '', action='store', dest="outfile",
+        metavar="OUTFILE",
+        help="Write the recorded coverage information to this file. Defaults to '.coverage'"
+    )
     json_pretty_print = optparse.make_option(
         '', '--pretty-print', action='store_true',
         help="Format the JSON for human readers.",
@@ -450,6 +456,7 @@ def get_prog_name(self):
             Opts.include,
             Opts.module,
             Opts.omit,
+            Opts.output_coverage,
             Opts.pylib,
             Opts.parallel_mode,
             Opts.source,
@@ -572,8 +579,11 @@ def command_line(self, argv):
         else:
             concurrency = None
 
+        data_file = options.outfile if options.action in ["run", "combine"] \
+            else getattr(options, "input_coverage", None)
         # Do something.
         self.coverage = Coverage(
+            data_file=data_file or DEFAULT_DATAFILE,
             data_suffix=options.parallel_mode,
             cover_pylib=options.pylib,
             timid=options.timid,

coverage/control.py

@@ -60,7 +60,8 @@ def override_config(cov, **kwargs):
         cov.config = original_config
 
 
-_DEFAULT_DATAFILE = DefaultValue("MISSING")
+DEFAULT_DATAFILE = DefaultValue("MISSING")
+_DEFAULT_DATAFILE = DEFAULT_DATAFILE  # Just in case, for backwards compatibility
 
 class Coverage:
     """Programmatic access to coverage.py.
@@ -101,7 +102,7 @@ def current(cls):
             return None
 
     def __init__(
-        self, data_file=_DEFAULT_DATAFILE, data_suffix=None, cover_pylib=None,
+        self, data_file=DEFAULT_DATAFILE, data_suffix=None, cover_pylib=None,
         auto_data=False, timid=None, branch=None, config_file=True,
         source=None, source_pkgs=None, omit=None, include=None, debug=None,
         concurrency=None, check_preimported=False, context=None,
@@ -198,7 +199,7 @@ def __init__(
         # data_file=None means no disk file at all. data_file missing means
         # use the value from the config file.
         self._no_disk = data_file is None
-        if data_file is _DEFAULT_DATAFILE:
+        if data_file is DEFAULT_DATAFILE:
             data_file = None
 
         self.config = None

tests/test_cmdline.py

@@ -14,6 +14,7 @@
 import coverage
 import coverage.cmdline
 from coverage import env
+from coverage.control import DEFAULT_DATAFILE
 from coverage.config import CoverageConfig
 from coverage.exceptions import _ExceptionDuringRun
 from coverage.version import __url__
@@ -53,6 +54,7 @@ class BaseCmdLineTest(CoverageTest):
         contexts=None, pretty_print=None, show_contexts=None,
     )
     _defaults.Coverage(
+        data_file=DEFAULT_DATAFILE,
         cover_pylib=None, data_suffix=None, timid=None, branch=None,
         config_file=True, source=None, include=None, omit=None, debug=None,
         concurrency=None, check_preimported=True, context=None, messages=True,
@@ -636,6 +638,15 @@ def test_run(self):
             cov.stop()
             cov.save()
             """)
+        self.cmd_executes("run -o output.coverage foo.py", """\
+            cov = Coverage(data_file="output.coverage")
+            runner = PyRunner(['foo.py'], as_module=False)
+            runner.prepare()
+            cov.start()
+            runner.run()
+            cov.stop()
+            cov.save()
+            """)
 
     def test_multiprocessing_needs_config_file(self):
         # You can't use command-line args to add options to multiprocessing