Fix coverage target breakage and add a test for it.

ciimage/Dockerfile

@@ -10,4 +10,5 @@ RUN apt-get -y update && apt-get -y upgrade \
 && apt-get -y install python3-pip libxml2-dev libxslt1-dev cmake libyaml-dev \
 && apt-get -y install openmpi-bin libopenmpi-dev \
 && apt-get -y install libvulkan-dev libpcap-dev \
+&& apt-get -y install gcovr lcov \
 && python3 -m pip install hotdoc codecov

mesonbuild/backend/ninjabackend.py

@@ -626,7 +626,7 @@ int dummy;
             added_rule = True
             htmloutdir = os.path.join(self.environment.get_log_dir(), 'coveragereport')
             covinfo = os.path.join(self.environment.get_log_dir(), 'coverage.info')
-            phony_elem = NinjaBuildElement(self.all_outputs, 'coverage-html', 'phony', os.path.join(htmloutdir, 'index.html'))
+            phony_elem = NinjaBuildElement(self.all_outputs, 'meson-coverage-html', 'phony', os.path.join(htmloutdir, 'index.html'))
             phony_elem.write(outfile)
             # Alias that runs the target defined above
             self.create_target_alias('meson-coverage-html', outfile)

run_unittests.py

@@ -1910,6 +1910,19 @@ class LinuxlikeTests(BasePlatformTests):
         for i in compdb:
             self.assertIn("-fsanitize=address", i["command"])
 
+    def test_coverage(self):
+        if not shutil.which('gcovr'):
+            raise unittest.SkipTest('gcovr not found')
+        if not shutil.which('genhtml'):
+            raise unittest.SkipTest('genhtml not found')
+        if 'clang' in os.environ.get('CC', '') and os.environ.get('TRAVIS_OS_NAME', '') == 'linux':
+            raise unittest.SkipTest('Gcovr has a bug and does not work with Clang in the CI environment.')
+        testdir = os.path.join(self.common_test_dir, '1 trivial')
+        self.init(testdir, ['-Db_coverage=true'])
+        self.build()
+        self.run_tests()
+        self.run_target('coverage-html')
+
 class LinuxArmCrossCompileTests(BasePlatformTests):
     '''
     Tests that verify cross-compilation to Linux/ARM