feat(config): reorder configuration precedence (TheKevJames#249)

We've been getting a slew of cases where users are reporting requiring
different configurations -- especially Github Actions, where we seem to
need to set a different service name on a case-by-case basis.

Reordering our configuration precedence such that user-specified values
overwrite the CI defaults should allow users to fix these problems
without requiring a one-size-fits-all code change.

This is massively backwards incompatible for anyone with the same key
set to two different values in their configs.

coveralls/api.py

@@ -18,6 +18,7 @@
 
 
 class Coveralls:
+    # pylint: disable=too-many-public-methods
     config_filename = '.coveralls.yml'
 
     def __init__(self, token_required=True, service_name=None, **kwargs):
@@ -40,39 +41,46 @@ def __init__(self, token_required=True, service_name=None, **kwargs):
         self._data = None
         self._coveralls_host = 'https://coveralls.io/'
         self._token_required = token_required
+        self.config = {}
 
-        self.config = self.load_config_from_file()
-        self.config.update(kwargs)
-        if service_name:
-            self.config['service_name'] = service_name
-        if self.config.get('coveralls_host'):
-            self._coveralls_host = self.config['coveralls_host']
-            del self.config['coveralls_host']
-
-        self.load_config_from_environment()
-
-        name, job, number, pr = self.load_config_from_ci_environment()
-        self.config['service_name'] = self.config.get('service_name', name)
-        if job or os.environ.get('GITHUB_ACTIONS'):
-            # N.B. Github Actions fails if this is not set even when null.
-            # Other services fail if this is set to null. Sigh.
-            self.config['service_job_id'] = job
-        if number:
-            self.config['service_number'] = number
-        if pr:
-            self.config['service_pull_request'] = pr
-
+        self.load_config(kwargs, service_name)
         self.ensure_token()
 
     def ensure_token(self):
         if self.config.get('repo_token') or not self._token_required:
             return
 
+        if os.environ.get('GITHUB_ACTIONS'):
+            raise CoverallsException(
+                'Running on Github Actions but GITHUB_TOKEN is not set. '
+                'Add "env: GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}" to '
+                'your step config.')
+
         raise CoverallsException(
             'Not on TravisCI. You have to provide either repo_token in {} or '
             'set the COVERALLS_REPO_TOKEN env var.'.format(
                 self.config_filename))
 
+    def load_config(self, kwargs, service_name):
+        """
+        Loads all coveralls configuration in the following precedence order.
+
+            1. automatic CI configuration
+            2. COVERALLS_* env vars
+            3. .coveralls.yml config file
+            4. CLI flags
+        """
+        self.load_config_from_ci_environment()
+        self.load_config_from_environment()
+        self.load_config_from_file()
+        self.config.update(kwargs)
+        if self.config.get('coveralls_host'):
+            # N.B. users can set --coveralls-host via CLI, but we don't keep
+            # that in the config
+            self._coveralls_host = self.config.pop('coveralls_host')
+        if service_name:
+            self.config['service_name'] = service_name
+
     @staticmethod
     def load_config_from_appveyor():
         pr = os.environ.get('APPVEYOR_PULL_REQUEST_NUMBER')
@@ -92,23 +100,19 @@ def load_config_from_circle():
         return 'circle-ci', os.environ.get('CIRCLE_BUILD_NUM'), number, pr
 
     def load_config_from_github(self):
-        service = 'github'
-        if self.config.get('repo_token'):
-            service = 'github-actions'
-        else:
-            gh_token = os.environ.get('GITHUB_TOKEN')
-            if not gh_token:
-                raise CoverallsException(
-                    'Running on Github Actions but GITHUB_TOKEN is not set. '
-                    'Add "env: GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}" to '
-                    'your step config.')
-            self.config['repo_token'] = gh_token
-
-        number = os.environ.get('GITHUB_RUN_ID')
+        # Github tokens and standard Coveralls tokens are almost but not quite
+        # the same -- forceibly using Github's flow seems to be more stable
+        self.config['repo_token'] = os.environ.get('GITHUB_TOKEN')
+
         pr = None
         if os.environ.get('GITHUB_REF', '').startswith('refs/pull/'):
             pr = os.environ.get('GITHUB_REF', '//').split('/')[2]
-        return service, None, number, pr
+
+        # N.B. some users require this to be 'github' and some require it to
+        # be 'github-actions'. Defaulting to 'github-actions' as it seems more
+        # common -- users can specify the service name manually to override
+        # this.
+        return 'github-actions', None, os.environ.get('GITHUB_RUN_ID'), pr
 
     @staticmethod
     def load_config_from_jenkins():
@@ -148,6 +152,9 @@ def load_config_from_ci_environment(self):
         elif os.environ.get('CIRCLECI'):
             name, job, number, pr = self.load_config_from_circle()
         elif os.environ.get('GITHUB_ACTIONS'):
+            # N.B. Github Actions fails if this is not set even when null.
+            # Other services fail if this is set to null. Sigh.
+            self.config['service_job_id'] = None
             name, job, number, pr = self.load_config_from_github()
         elif os.environ.get('JENKINS_HOME'):
             name, job, number, pr = self.load_config_from_jenkins()
@@ -158,7 +165,14 @@ def load_config_from_ci_environment(self):
             name, job, number, pr = self.load_config_from_semaphore()
         else:
             name, job, number, pr = self.load_config_from_unknown()
-        return (name, job, number, pr)
+
+        self.config['service_name'] = name
+        if job:
+            self.config['service_job_id'] = job
+        if number:
+            self.config['service_number'] = number
+        if pr:
+            self.config['service_pull_request'] = pr
 
     def load_config_from_environment(self):
         coveralls_host = os.environ.get('COVERALLS_HOST')
@@ -191,16 +205,14 @@ def load_config_from_file(self):
                                    self.config_filename)) as config:
                 try:
                     import yaml  # pylint: disable=import-outside-toplevel
-                    return yaml.safe_load(config)
+                    self.config.update(yaml.safe_load(config))
                 except ImportError:
                     log.warning('PyYAML is not installed, skipping %s.',
                                 self.config_filename)
         except OSError:
             log.debug('Missing %s file. Using only env variables.',
                       self.config_filename)
 
-        return {}
-
     def merge(self, path):
         reader = codecs.getreader('utf-8')
         with open(path, 'rb') as fh:

docs/usage/configuration.rst

@@ -3,9 +3,22 @@
 Configuration
 =============
 
-coveralls-python often works without any outside configuration by examining the environment it is being run in. Special handling has been added for AppVeyor, BuildKite, CircleCI, Github Actions, Jenkins, and TravisCI to make coveralls-python as close to "plug and play" as possible.
+coveralls-python often works without any outside configuration by examining the
+environment it is being run in. Special handling has been added for AppVeyor,
+BuildKite, CircleCI, Github Actions, Jenkins, and TravisCI to make
+coveralls-python as close to "plug and play" as possible.
 
-Most often, you will simply need to run coveralls-python with no additional options after you have run your coverage suite::
+In cases where you do need to modify the configuration, we obey a very strict
+precedence order where the **latest value is used**:
+
+* first, the CI environment will be loaded
+* second, any environment variables will be loaded (eg. those which begin with
+  ``COVERALLS_``
+* third, the config file is loaded (eg. ``./..coveralls.yml``)
+* finally, any command line flags are evaluated
+
+Most often, you will simply need to run coveralls-python with no additional
+options after you have run your coverage suite::
 
     coveralls
 
@@ -68,6 +81,10 @@ Passing a coveralls.io token via the ``COVERALLS_REPO_TOKEN`` environment variab
 (or via the ``repo_token`` parameter in the config file) is not needed for
 Github Actions.
 
+Sometimes Github Actions gets a little picky about the service name which needs to
+be used in various cases. If you run into issues, try setting the ``COVERALLS_SERVICE_NAME``
+explicitly to either ``github`` or ``github-actions``.
+
 For parallel builds, you have to add a final step to let coveralls.io know the
 parallel build is finished::
 

tests/api/configuration_test.py

@@ -145,7 +145,7 @@ def test_github_no_config(self):
         clear=True)
     def test_github_no_config_no_pr(self):
         cover = Coveralls()
-        assert cover.config['service_name'] == 'github'
+        assert cover.config['service_name'] == 'github-actions'
         assert cover.config['service_number'] == '987654321'
         assert 'service_job_id' in cover.config
         assert 'service_pull_request' not in cover.config