Make file operations implicit on constructed filename

6 files changed, 83 insertions, 75 deletions

diff --git a/coverage/data.py b/coverage/data.py
index 6d30e2ba..23e612a1 100644
--- a/coverage/data.py
+++ b/coverage/data.py
@@ -57,7 +57,10 @@ class CoverageData(object):
     names in this API are case-sensitive, even on platforms with
     case-insensitive file systems.
 
-    To read a coverage.py data file, use :meth:`read_file`.  You can then
+    A data file is associated with the data when the :class:`CoverageData`
+    is created.
+
+    To read a coverage.py data file, use :meth:`read`.  You can then
     access the line, arc, or file tracer data with :meth:`lines`, :meth:`arcs`,
     or :meth:`file_tracer`.  Run information is available with
     :meth:`run_infos`.
@@ -68,16 +71,15 @@ class CoverageData(object):
     most Python containers, you can determine if there is any data at all by
     using this object as a boolean value.
 
-
     Most data files will be created by coverage.py itself, but you can use
     methods here to create data files if you like.  The :meth:`add_lines`,
     :meth:`add_arcs`, and :meth:`add_file_tracers` methods add data, in ways
     that are convenient for coverage.py.  The :meth:`add_run_info` method adds
     key-value pairs to the run information.
 
-    To add a file without any measured data, use :meth:`touch_file`.
+    To add a source file without any measured data, use :meth:`touch_file`.
 
-    You write to a named file with :meth:`write_file`.
+    Write the data to its file with :meth:`write`.
 
     You can clear the data in memory with :meth:`erase`.  Two data collections
     can be combined by using :meth:`update` on one :class:`CoverageData`,
@@ -267,9 +269,13 @@ class CoverageData(object):
     __bool__ = __nonzero__
 
     def read(self):
-        """Read the coverage data."""
+        """Read the coverage data.
+
+        It is fine for the file to not exist, in which case no data is read.
+
+        """
         if os.path.exists(self.filename):
-            self.read_file(self.filename)
+            self._read_file(self.filename)
 
     def _read_fileobj(self, file_obj):
         """Read the coverage data from the given file object.
@@ -293,7 +299,7 @@ class CoverageData(object):
 
         self._validate()
 
-    def read_file(self, filename):
+    def _read_file(self, filename):
         """Read the coverage data from `filename` into this object."""
         if self._debug and self._debug.should('dataio'):
             self._debug.write("Reading data from %r" % (filename,))
@@ -472,7 +478,7 @@ class CoverageData(object):
 
         if suffix:
             filename += "." + suffix
-        self.write_file(filename)
+        self._write_file(filename)
 
     def _write_fileobj(self, file_obj):
         """Write the coverage data to `file_obj`."""
@@ -496,7 +502,7 @@ class CoverageData(object):
         file_obj.write(self._GO_AWAY)
         json.dump(file_data, file_obj, separators=(',', ':'))
 
-    def write_file(self, filename):
+    def _write_file(self, filename):
         """Write the coverage data to `filename`."""
         if self._debug and self._debug.should('dataio'):
             self._debug.write("Writing data to %r" % (filename,))
@@ -635,7 +641,7 @@ class CoverageData(object):
         for f in files_to_combine:
             new_data = CoverageData(debug=self._debug)
             try:
-                new_data.read_file(f)
+                new_data._read_file(f)
             except CoverageException as exc:
                 if self._warn:
                     # The CoverageException has the file name in it, so just
diff --git a/tests/test_concurrency.py b/tests/test_concurrency.py
index 58529ec5..a4f700ed 100644
--- a/tests/test_concurrency.py
+++ b/tests/test_concurrency.py
@@ -235,8 +235,8 @@ class ConcurrencyTest(CoverageTest):
 
             # Read the coverage file and see that try_it.py has all its lines
             # executed.
-            data = coverage.CoverageData()
-            data.read_file(".coverage")
+            data = coverage.CoverageData(".coverage")
+            data.read()
 
             # If the test fails, it's helpful to see this info:
             fname = abs_file("try_it.py")
diff --git a/tests/test_data.py b/tests/test_data.py
index 3c0d602b..5deccef0 100644
--- a/tests/test_data.py
+++ b/tests/test_data.py
@@ -430,59 +430,58 @@ class CoverageDataTestInTempDir(DataTestHelpers, CoverageTest):
     """Tests of CoverageData that need a temporary directory to make files."""
 
     def test_read_write_lines(self):
-        covdata1 = CoverageData()
+        covdata1 = CoverageData("lines.dat")
         covdata1.add_lines(LINES_1)
-        covdata1.write_file("lines.dat")
+        covdata1.write()
 
-        covdata2 = CoverageData()
-        covdata2.read_file("lines.dat")
+        covdata2 = CoverageData("lines.dat")
+        covdata2.read()
         self.assert_lines1_data(covdata2)
 
     def test_read_write_arcs(self):
-        covdata1 = CoverageData()
+        covdata1 = CoverageData("arcs.dat")
         covdata1.add_arcs(ARCS_3)
-        covdata1.write_file("arcs.dat")
+        covdata1.write()
 
-        covdata2 = CoverageData()
-        covdata2.read_file("arcs.dat")
+        covdata2 = CoverageData("arcs.dat")
+        covdata2.read()
         self.assert_arcs3_data(covdata2)
 
     def test_read_errors(self):
-        covdata = CoverageData()
+        msg = r"Couldn't read data from '.*[/\\]{0}': \S+"
 
-        msg = r"Couldn't read data from '{0}': \S+"
         self.make_file("xyzzy.dat", "xyzzy")
         with self.assertRaisesRegex(CoverageException, msg.format("xyzzy.dat")):
-            covdata.read_file("xyzzy.dat")
+            covdata = CoverageData("xyzzy.dat")
+            covdata.read()
+        self.assertFalse(covdata)
 
         self.make_file("empty.dat", "")
         with self.assertRaisesRegex(CoverageException, msg.format("empty.dat")):
-            covdata.read_file("empty.dat")
-
-        with self.assertRaisesRegex(CoverageException, msg.format("nonexistent.dat")):
-            covdata.read_file("nonexistent.dat")
+            covdata = CoverageData("empty.dat")
+            covdata.read()
+        self.assertFalse(covdata)
 
         self.make_file("misleading.dat", CoverageData._GO_AWAY + " this isn't JSON")
         with self.assertRaisesRegex(CoverageException, msg.format("misleading.dat")):
-            covdata.read_file("misleading.dat")
-
-        # After all that, no data should be in our CoverageData.
+            covdata = CoverageData("misleading.dat")
+            covdata.read()
         self.assertFalse(covdata)
 
     def test_debug_main(self):
-        covdata1 = CoverageData()
+        covdata1 = CoverageData(".coverage")
         covdata1.add_lines(LINES_1)
-        covdata1.write_file(".coverage")
+        covdata1.write()
         debug_main([])
 
-        covdata2 = CoverageData()
+        covdata2 = CoverageData("arcs.dat")
         covdata2.add_arcs(ARCS_3)
         covdata2.add_file_tracers({"y.py": "magic_plugin"})
         covdata2.add_run_info(version="v3.14", chunks=["z", "a"])
-        covdata2.write_file("arcs.dat")
+        covdata2.write()
 
-        covdata3 = CoverageData()
-        covdata3.write_file("empty.dat")
+        covdata3 = CoverageData("empty.dat")
+        covdata3.write()
         debug_main(["arcs.dat", "empty.dat"])
 
         expected = {
@@ -725,20 +724,20 @@ class CoverageDataFilesTest(DataTestHelpers, CoverageTest):
         self.assertEqual(covdata3.file_tracer(template_html), 'html.plugin')
 
     def test_combining_from_different_directories(self):
-        covdata1 = CoverageData()
+        covdata1 = CoverageData('cov1/.coverage.1')
         covdata1.add_lines(LINES_1)
         os.makedirs('cov1')
-        covdata1.write_file('cov1/.coverage.1')
+        covdata1.write()
 
-        covdata2 = CoverageData()
+        covdata2 = CoverageData('cov2/.coverage.2')
         covdata2.add_lines(LINES_2)
         os.makedirs('cov2')
-        covdata2.write_file('cov2/.coverage.2')
+        covdata2.write()
 
         # This data won't be included.
-        covdata_xxx = CoverageData()
+        covdata_xxx = CoverageData('.coverage.xxx')
         covdata_xxx.add_arcs(ARCS_3)
-        covdata_xxx.write_file('.coverage.xxx')
+        covdata_xxx.write()
 
         covdata3 = CoverageData()
         covdata3.combine_parallel_data(data_paths=['cov1', 'cov2'])
@@ -750,21 +749,24 @@ class CoverageDataFilesTest(DataTestHelpers, CoverageTest):
         self.assert_exists(".coverage.xxx")
 
     def test_combining_from_files(self):
-        covdata1 = CoverageData()
+        covdata1 = CoverageData('cov1/.coverage.1')
         covdata1.add_lines(LINES_1)
         os.makedirs('cov1')
-        covdata1.write_file('cov1/.coverage.1')
+        covdata1.write()
 
-        covdata2 = CoverageData()
+        covdata2 = CoverageData('cov2/.coverage.2')
         covdata2.add_lines(LINES_2)
         os.makedirs('cov2')
-        covdata2.write_file('cov2/.coverage.2')
+        covdata2.write()
 
         # This data won't be included.
-        covdata_xxx = CoverageData()
+        covdata_xxx = CoverageData('.coverage.xxx')
         covdata_xxx.add_arcs(ARCS_3)
-        covdata_xxx.write_file('.coverage.xxx')
-        covdata_xxx.write_file('cov2/.coverage.xxx')
+        covdata_xxx.write()
+
+        covdata_2xxx = CoverageData('cov2/.coverage.xxx')
+        covdata_2xxx.add_arcs(ARCS_3)
+        covdata_2xxx.write()
 
         covdata3 = CoverageData()
         covdata3.combine_parallel_data(data_paths=['cov1', 'cov2/.coverage.2'])
diff --git a/tests/test_debug.py b/tests/test_debug.py
index 2699ca61..c46e3dae 100644
--- a/tests/test_debug.py
+++ b/tests/test_debug.py
@@ -136,10 +136,10 @@ class DebugTraceTest(CoverageTest):
         self.assertEqual(len(real_messages), len(frames))
 
         # The last message should be "Writing data", and the last frame should
-        # be write_file in data.py.
+        # be _write_file in data.py.
         self.assertRegex(real_messages[-1], r"^\s*\d+\.\w{4}: Writing data")
         last_line = out_lines.splitlines()[-1]
-        self.assertRegex(last_line, r"\s+write_file : .*coverage[/\\]data.py @\d+$")
+        self.assertRegex(last_line, r"\s+_write_file : .*coverage[/\\]data.py @\d+$")
 
     def test_debug_config(self):
         out_lines = self.f1_debug_output(["config"])
diff --git a/tests/test_process.py b/tests/test_process.py
index e022e727..341ad37c 100644
--- a/tests/test_process.py
+++ b/tests/test_process.py
@@ -98,7 +98,7 @@ class ProcessTest(CoverageTest):
         # Read the coverage file and see that b_or_c.py has all 8 lines
         # executed.
         data = coverage.CoverageData()
-        data.read_file(".coverage")
+        data.read()
         self.assertEqual(data.line_counts()['b_or_c.py'], 8)
 
         # Running combine again should fail, because there are no parallel data
@@ -109,7 +109,7 @@ class ProcessTest(CoverageTest):
 
         # And the originally combined data is still there.
         data = coverage.CoverageData()
-        data.read_file(".coverage")
+        data.read()
         self.assertEqual(data.line_counts()['b_or_c.py'], 8)
 
     def test_combine_parallel_data_with_a_corrupt_file(self):
@@ -145,7 +145,7 @@ class ProcessTest(CoverageTest):
         # Read the coverage file and see that b_or_c.py has all 8 lines
         # executed.
         data = coverage.CoverageData()
-        data.read_file(".coverage")
+        data.read()
         self.assertEqual(data.line_counts()['b_or_c.py'], 8)
 
     def test_combine_no_usable_files(self):
@@ -179,7 +179,7 @@ class ProcessTest(CoverageTest):
         # Read the coverage file and see that b_or_c.py has 6 lines
         # executed (we only did b, not c).
         data = coverage.CoverageData()
-        data.read_file(".coverage")
+        data.read()
         self.assertEqual(data.line_counts()['b_or_c.py'], 6)
 
     def test_combine_parallel_data_in_two_steps(self):
@@ -210,7 +210,7 @@ class ProcessTest(CoverageTest):
         # Read the coverage file and see that b_or_c.py has all 8 lines
         # executed.
         data = coverage.CoverageData()
-        data.read_file(".coverage")
+        data.read()
         self.assertEqual(data.line_counts()['b_or_c.py'], 8)
 
     def test_combine_parallel_data_no_append(self):
@@ -242,7 +242,7 @@ class ProcessTest(CoverageTest):
         # Read the coverage file and see that b_or_c.py has only 7 lines
         # because we didn't keep the data from running b.
         data = coverage.CoverageData()
-        data.read_file(".coverage")
+        data.read()
         self.assertEqual(data.line_counts()['b_or_c.py'], 7)
 
     def test_append_data(self):
@@ -261,7 +261,7 @@ class ProcessTest(CoverageTest):
         # Read the coverage file and see that b_or_c.py has all 8 lines
         # executed.
         data = coverage.CoverageData()
-        data.read_file(".coverage")
+        data.read()
         self.assertEqual(data.line_counts()['b_or_c.py'], 8)
 
     def test_append_data_with_different_file(self):
@@ -284,8 +284,8 @@ class ProcessTest(CoverageTest):
 
         # Read the coverage file and see that b_or_c.py has all 8 lines
         # executed.
-        data = coverage.CoverageData()
-        data.read_file(".mycovdata")
+        data = coverage.CoverageData(".mycovdata")
+        data.read()
         self.assertEqual(data.line_counts()['b_or_c.py'], 8)
 
     def test_append_can_create_a_data_file(self):
@@ -299,7 +299,7 @@ class ProcessTest(CoverageTest):
         # Read the coverage file and see that b_or_c.py has only 6 lines
         # executed.
         data = coverage.CoverageData()
-        data.read_file(".coverage")
+        data.read()
         self.assertEqual(data.line_counts()['b_or_c.py'], 6)
 
     def test_combine_with_rc(self):
@@ -332,7 +332,7 @@ class ProcessTest(CoverageTest):
         # Read the coverage file and see that b_or_c.py has all 8 lines
         # executed.
         data = coverage.CoverageData()
-        data.read_file(".coverage")
+        data.read()
         self.assertEqual(data.line_counts()['b_or_c.py'], 8)
 
         # Reporting should still work even with the .rc file
@@ -386,7 +386,7 @@ class ProcessTest(CoverageTest):
         # Read the coverage data file and see that the two different x.py
         # files have been combined together.
         data = coverage.CoverageData()
-        data.read_file(".coverage")
+        data.read()
         summary = data.line_counts(fullpath=True)
         self.assertEqual(len(summary), 1)
         actual = os.path.normcase(os.path.abspath(list(summary.keys())[0]))
@@ -549,7 +549,7 @@ class ProcessTest(CoverageTest):
         self.assertEqual(self.number_of_data_files(), 1)
 
         data = coverage.CoverageData()
-        data.read_file(".coverage")
+        data.read()
         self.assertEqual(data.line_counts()['fork.py'], 9)
 
     def test_warnings_during_reporting(self):
@@ -655,8 +655,8 @@ class ProcessTest(CoverageTest):
         self.make_file("simple.py", """print('hello')""")
         self.run_command("coverage run simple.py")
 
-        data = CoverageData()
-        data.read_file("mydata.dat")
+        data = CoverageData("mydata.dat")
+        data.read()
         infos = data.run_infos()
         self.assertEqual(len(infos), 1)
         expected = u"These are musical notes: ♫𝅗𝅥♩"
@@ -686,7 +686,7 @@ class ProcessTest(CoverageTest):
         out = self.run_command("python -m coverage run -L getenv.py")
         self.assertEqual(out, "FOOEY == BOO\n")
         data = coverage.CoverageData()
-        data.read_file(".coverage")
+        data.read()
         # The actual number of executed lines in os.py when it's
         # imported is 120 or so.  Just running os.getenv executes
         # about 5.
@@ -916,7 +916,7 @@ class ExcepthookTest(CoverageTest):
         # Read the coverage file and see that excepthook.py has 7 lines
         # executed.
         data = coverage.CoverageData()
-        data.read_file(".coverage")
+        data.read()
         self.assertEqual(data.line_counts()['excepthook.py'], 7)
 
     def test_excepthook_exit(self):
@@ -1245,9 +1245,9 @@ class ProcessStartupTest(ProcessCoverageMixin, CoverageTest):
         # An existing data file should not be read when a subprocess gets
         # measured automatically.  Create the data file here with bogus data in
         # it.
-        data = coverage.CoverageData()
+        data = coverage.CoverageData(".mycovdata")
         data.add_lines({os.path.abspath('sub.py'): dict.fromkeys(range(100))})
-        data.write_file(".mycovdata")
+        data.write()
 
         self.make_file("coverage.ini", """\
             [run]
@@ -1261,8 +1261,8 @@ class ProcessStartupTest(ProcessCoverageMixin, CoverageTest):
 
         # Read the data from .coverage
         self.assert_exists(".mycovdata")
-        data = coverage.CoverageData()
-        data.read_file(".mycovdata")
+        data = coverage.CoverageData(".mycovdata")
+        data.read()
         self.assertEqual(data.line_counts()['sub.py'], 3)
 
     def test_subprocess_with_pth_files_and_parallel(self):  # pragma: no metacov
@@ -1286,7 +1286,7 @@ class ProcessStartupTest(ProcessCoverageMixin, CoverageTest):
         # assert that the combined .coverage data file is correct
         self.assert_exists(".coverage")
         data = coverage.CoverageData()
-        data.read_file(".coverage")
+        data.read()
         self.assertEqual(data.line_counts()['sub.py'], 3)
 
         # assert that there are *no* extra data files left over after a combine
@@ -1376,7 +1376,7 @@ class ProcessStartupWithSourceTest(ProcessCoverageMixin, CoverageTest):
         # Read the data from .coverage
         self.assert_exists(".coverage")
         data = coverage.CoverageData()
-        data.read_file(".coverage")
+        data.read()
         summary = data.line_counts()
         print(summary)
         self.assertEqual(summary[source + '.py'], 3)
diff --git a/tests/test_summary.py b/tests/test_summary.py
index b2895370..980fd3d4 100644
--- a/tests/test_summary.py
+++ b/tests/test_summary.py
@@ -161,7 +161,7 @@ class SummaryTest(UsingModulesMixin, CoverageTest):
 
         # Read the data written, to see that the right files have been omitted from running.
         covdata = CoverageData()
-        covdata.read_file(".coverage")
+        covdata.read()
         files = [os.path.basename(p) for p in covdata.measured_files()]
         self.assertIn("covmod1.py", files)
         self.assertNotIn("covmodzip1.py", files)