feat: `coverage combine` now prints messages naming the files being combined. #1105 (#1208)

5 files changed, 32 insertions, 13 deletions

diff --git a/CHANGES.rst b/CHANGES.rst
index 7977b1a5..600c71f8 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -27,6 +27,9 @@ Unreleased
 - The ``coverage html`` command now prints a message indicating where the HTML
   report was written.  Fixes `issue 1195`_.
 
+- The ``coverage combine`` command now prints messages indicating each data
+  file being combined.  Fixes `issue 1105`_.
+
 - Unrecognized options in the configuration file are no longer errors. They are
   now warnings, to ease the use of coverage across versions.  Fixes `issue
   1035`_.
@@ -35,6 +38,7 @@ Unreleased
   unsupported type." (`issue 1010`_).
 
 .. _issue 1035: https://github.com/nedbat/coveragepy/issues/1035
+.. _issue 1105: https://github.com/nedbat/coveragepy/issues/1105
 .. _issue 1195: https://github.com/nedbat/coveragepy/issues/1195
 
 
diff --git a/coverage/control.py b/coverage/control.py
index 958c98da..8a55a317 100644
--- a/coverage/control.py
+++ b/coverage/control.py
@@ -718,6 +718,7 @@ class Coverage:
             data_paths=data_paths,
             strict=strict,
             keep=keep,
+            message=self._message,
         )
 
     def get_data(self):
diff --git a/coverage/data.py b/coverage/data.py
index 752822b7..68ba7ec3 100644
--- a/coverage/data.py
+++ b/coverage/data.py
@@ -53,7 +53,9 @@ def add_data_to_hash(data, filename, hasher):
     hasher.update(data.file_tracer(filename))
 
 
-def combine_parallel_data(data, aliases=None, data_paths=None, strict=False, keep=False):
+def combine_parallel_data(
+    data, aliases=None, data_paths=None, strict=False, keep=False, message=None,
+):
     """Combine a number of data files together.
 
     Treat `data.filename` as a file prefix, and combine the data from all
@@ -117,6 +119,8 @@ def combine_parallel_data(data, aliases=None, data_paths=None, strict=False, kee
         else:
             data.update(new_data, aliases=aliases)
             files_combined += 1
+            if message:
+                message(f"Combined data file {os.path.relpath(f)}")
             if not keep:
                 if data._debug.should('dataio'):
                     data._debug.write(f"Deleting combined data file {f!r}")
diff --git a/tests/test_api.py b/tests/test_api.py
index 885f3370..5f7b3522 100644
--- a/tests/test_api.py
+++ b/tests/test_api.py
@@ -437,6 +437,7 @@ class ApiTest(CoverageTest):
         self.make_good_data_files()
         cov1 = coverage.Coverage()
         cov1.combine()
+        assert self.stdout() == ""
         cov1.save()
         self.check_code1_code2(cov1)
         self.assert_file_count(".coverage.*", 0)
@@ -448,6 +449,7 @@ class ApiTest(CoverageTest):
 
         cov3 = coverage.Coverage()
         cov3.combine()
+        assert self.stdout() == ""
         # Now the data is empty!
         _, statements, missing, _ = cov3.analysis("code1.py")
         assert statements == [1]
@@ -469,6 +471,7 @@ class ApiTest(CoverageTest):
         cov.save()
 
         cov.combine()
+        assert self.stdout() == ""
         self.check_code1_code2(cov)
 
     def test_ordered_combine(self):
@@ -483,6 +486,7 @@ class ApiTest(CoverageTest):
         def get_combined_filenames():
             cov = coverage.Coverage()
             cov.combine()
+            assert self.stdout() == ""
             cov.save()
             data = cov.get_data()
             filenames = {relative_filename(f).replace("\\", "/") for f in data.measured_files()}
diff --git a/tests/test_concurrency.py b/tests/test_concurrency.py
index e1606e83..682e3cf0 100644
--- a/tests/test_concurrency.py
+++ b/tests/test_concurrency.py
@@ -392,7 +392,12 @@ class MultiprocessingTest(CoverageTest):
                 assert len(glob.glob(".coverage.*")) == nprocs + 1
 
                 out = self.run_command("coverage combine")
-                assert out == ""
+                out_lines = out.splitlines()
+                assert len(out_lines) == nprocs + 1
+                assert all(
+                    re.fullmatch(r"Combined data file \.coverage\..*\.\d+\.\d+", line)
+                    for line in out_lines
+                )
                 out = self.run_command("coverage report -m")
 
                 last_line = self.squeezed_lines(out)[-1]
@@ -426,8 +431,12 @@ class MultiprocessingTest(CoverageTest):
             code, expected_out, eventlet, nprocs, concurrency="multiprocessing,eventlet"
         )
 
-    def try_multiprocessing_code_with_branching(self, code, expected_out):
-        """Run code using multiprocessing, it should produce `expected_out`."""
+    def test_multiprocessing_with_branching(self):
+        nprocs = 3
+        upto = 30
+        code = (SQUARE_OR_CUBE_WORK + MULTI_CODE).format(NPROCS=nprocs, UPTO=upto)
+        total = sum(x*x if x%2 else x*x*x for x in range(upto))
+        expected_out = f"{nprocs} pids, total = {total}"
         self.make_file("multi.py", code)
         self.make_file("multi.rc", """\
             [run]
@@ -444,20 +453,17 @@ class MultiprocessingTest(CoverageTest):
             assert out.rstrip() == expected_out
 
             out = self.run_command("coverage combine")
-            assert out == ""
+            out_lines = out.splitlines()
+            assert len(out_lines) == nprocs + 1
+            assert all(
+                re.fullmatch(r"Combined data file \.coverage\..*\.\d+\.\d+", line)
+                for line in out_lines
+            )
             out = self.run_command("coverage report -m")
 
             last_line = self.squeezed_lines(out)[-1]
             assert re.search(r"TOTAL \d+ 0 \d+ 0 100%", last_line)
 
-    def test_multiprocessing_with_branching(self):
-        nprocs = 3
-        upto = 30
-        code = (SQUARE_OR_CUBE_WORK + MULTI_CODE).format(NPROCS=nprocs, UPTO=upto)
-        total = sum(x*x if x%2 else x*x*x for x in range(upto))
-        expected_out = f"{nprocs} pids, total = {total}"
-        self.try_multiprocessing_code_with_branching(code, expected_out)
-
     def test_multiprocessing_bootstrap_error_handling(self):
         # An exception during bootstrapping will be reported.
         self.make_file("multi.py", """\