feat(api): support generic CI env vars (TheKevJames#299)

The official docs for Coveralls define a set of generic environment
variables that once defined should support any CI environment:

https://docs.coveralls.io/supported-ci-services (bottom of the page).

The changes implemented in this PR attempt to read those variables
but allows the values to be overwritten by any CI-specific configuration
currently supported. They were also inspired by the official client
(coveralls-ruby - lib/coveralls/configuration.rb -
set_standard_service_params_for_generic_ci).

coveralls/api.py

@@ -16,6 +16,8 @@
 
 log = logging.getLogger('coveralls.api')
 
+NUMBER_REGEX = re.compile(r'(\d+)$', re.IGNORECASE)
+
 
 class Coveralls:
     # pylint: disable=too-many-public-methods
@@ -144,7 +146,33 @@ def load_config_from_semaphore():
     def load_config_from_unknown():
         return 'coveralls-python', None, None, None
 
+    def load_config_from_generic_ci_environment(self):
+        # Inspired by the official client:
+        # coveralls-ruby in lib/coveralls/configuration.rb
+        # (set_standard_service_params_for_generic_ci)
+
+        config = {
+            'service_name': os.environ.get('CI_NAME'),
+            'service_number': os.environ.get('CI_BUILD_NUMBER'),
+            'service_build_url': os.environ.get('CI_BUILD_URL'),
+            'service_job_id': os.environ.get('CI_JOB_ID'),
+            'service_branch': os.environ.get('CI_BRANCH'),
+        }
+
+        pr_match = NUMBER_REGEX.findall(os.environ.get('CI_PULL_REQUEST', ''))
+        if pr_match:
+            config['service_pull_request'] = pr_match[-1]
+
+        non_empty = {key: value for key, value in config.items() if value}
+        self.config.update(non_empty)
+
     def load_config_from_ci_environment(self):
+        # As defined at the bottom of
+        # https://docs.coveralls.io/supported-ci-services
+        # there are a few env vars that should support any arbitrary CI.
+        # We load them first and allow more specific vars to overwrite
+        self.load_config_from_generic_ci_environment()
+
         if os.environ.get('APPVEYOR'):
             name, job, number, pr = self.load_config_from_appveyor()
         elif os.environ.get('BUILDKITE'):
@@ -166,7 +194,7 @@ def load_config_from_ci_environment(self):
         else:
             name, job, number, pr = self.load_config_from_unknown()
 
-        self.config['service_name'] = name
+        self.config.setdefault('service_name', name)
         if job:
             self.config['service_job_id'] = job
         if number:

docs/usage/configuration.rst

@@ -156,3 +156,27 @@ you can copy from the coveralls.io website).
 As per `#245 <https://github.com/TheKevJames/coveralls-python/issues/245>`_,
 our users suggest leaving "keep this value secret" unchecked -- this may be
 secure enough as-is, in that a user making a PR cannot access this variable.
+
+Other CI systems
+----------------
+
+As specified in the Coveralls `official docs
+<https://docs.coveralls.io/supported-ci-services>`
+other CI systems can be supported if the following environment variables are
+defined::
+
+    CI_NAME
+        # Name of the CI service being used
+    CI_BUILD_NUMBER
+        # Number (counter) relative to the current build
+    CI_BUILD_URL
+        # URL to a webpage showing the build information/output
+    CI_BRANCH
+        # For pull requests this is the name of the branch targeted by the PR,
+        # otherwise it corresponds to the name of the current branch or tag
+    CI_JOB_ID (optional)
+        # Unique identifier of the job in the CI service.
+        # When missing, CI_BUILD_NUMBER is used
+    CI_PULL_REQUEST (optional)
+        # If given, corresponds to the number of the pull request, as specified
+        # in the supported repository hosting service (GitHub, GitLab, etc)

tests/api/configuration_test.py

@@ -198,6 +198,40 @@ def test_semaphore_20_no_config(self):
         assert cover.config['service_number'] == 'b86b3adf'
         assert cover.config['service_pull_request'] == '9999'
 
+    @mock.patch.dict(
+        os.environ,
+        {'CI_NAME': 'generic-ci',
+         'CI_PULL_REQUEST': 'pull/1234',
+         'CI_JOB_ID': 'bb0e00166',
+         'CI_BUILD_NUMBER': '3',
+         'CI_BUILD_URL': 'https://generic-ci.local/build/123456789',
+         'CI_BRANCH': 'fixup-branch',
+         'COVERALLS_REPO_TOKEN': 'xxx'},
+        clear=True)
+    def test_generic_no_config(self):
+        cover = Coveralls()
+        assert cover.config['service_name'] == 'generic-ci'
+        assert cover.config['service_job_id'] == 'bb0e00166'
+        assert cover.config['service_branch'] == 'fixup-branch'
+        assert cover.config['service_pull_request'] == '1234'
+
+    @mock.patch.dict(
+        os.environ,
+        {'CI_NAME': 'generic-ci',
+         'CI_PULL_REQUEST': '',
+         'CI_JOB_ID': 'bb0e00166',
+         'CI_BUILD_NUMBER': '3',
+         'CI_BUILD_URL': 'https://generic-ci.local/build/123456789',
+         'CI_BRANCH': 'fixup-branch',
+         'COVERALLS_REPO_TOKEN': 'xxx'},
+        clear=True)
+    def test_generic_no_config_no_pr(self):
+        cover = Coveralls()
+        assert cover.config['service_name'] == 'generic-ci'
+        assert cover.config['service_job_id'] == 'bb0e00166'
+        assert cover.config['service_branch'] == 'fixup-branch'
+        assert 'service_pull_request' not in cover.config
+
     @mock.patch.dict(os.environ, {'COVERALLS_SERVICE_NAME': 'xxx'}, clear=True)
     def test_service_name_from_env(self):
         cover = Coveralls(repo_token='yyy')