fix: [tools.coverage] is valid for settings in a toml file. #1516

CHANGES.rst

@@ -20,9 +20,18 @@ development at the same time, such as 4.5.x and 5.0.
 Unreleased
 ----------
 
+- Fix: if Python doesn't provide tomllib, then TOML configuration files can
+  only be read if coverage.py is installed with the ``[toml]`` extra.
+  Coverage.py will raise an error if toml support is not installed when it sees
+  your settings are in a .toml file. But it didn't understand that
+  ``[tools.coverage]`` was a valid section header, so the error wasn't
+  reported, and settings were silently ignored.  This is now fixed, closing
+  `issue 1516`_.
+
 - Fix: adjusted how decorators are traced on PyPy 7.3.10, fixing `issue 1515`_.
 
 .. _issue 1515: https://github.com/nedbat/coveragepy/issues/1515
+.. _issue 1516: https://github.com/nedbat/coveragepy/issues/1516
 
 
 .. _changes_7-0-1:

coverage/tomlconfig.py

@@ -52,7 +52,7 @@ def read(self, filenames):
                 raise TomlDecodeError(str(err)) from err
             return [filename]
         else:
-            has_toml = re.search(r"^\[tool\.coverage\.", toml_text, flags=re.MULTILINE)
+            has_toml = re.search(r"^\[tool\.coverage(\.|])", toml_text, flags=re.MULTILINE)
             if self.our_file or has_toml:
                 # Looks like they meant to read TOML, but we can't read it.
                 msg = "Can't read {!r} without TOML support. Install with [toml] extra"

tests/test_config.py

@@ -739,6 +739,19 @@ def test_no_toml_installed_pyproject_toml(self):
             with pytest.raises(ConfigError, match=msg):
                 coverage.Coverage()
 
+    @pytest.mark.skipif(sys.version_info >= (3, 11), reason="Python 3.11 has toml in stdlib")
+    def test_no_toml_installed_pyproject_toml_shorter_syntax(self):
+        # Can't have coverage config in pyproject.toml without toml installed.
+        self.make_file("pyproject.toml", """\
+            # A toml file!
+            [tool.coverage]
+            run.parallel = true
+            """)
+        with without_module(coverage.tomlconfig, 'tomllib'):
+            msg = "Can't read 'pyproject.toml' without TOML support"
+            with pytest.raises(ConfigError, match=msg):
+                coverage.Coverage()
+
     def test_no_toml_installed_pyproject_no_coverage(self):
         # It's ok to have non-coverage pyproject.toml without toml installed.
         self.make_file("pyproject.toml", """\