Fix loading global cfgs (#312)

* Fix loading global cfgs + add tests

* Add docs about global config

* Update docs/source/basics.md

Co-Authored-By: michaelboulton <michaelboulton@users.noreply.github.com>

* Update tavern/core.py

Co-Authored-By: michaelboulton <michaelboulton@users.noreply.github.com>

* Split loading config into separate helper

* formatting

docs/source/basics.md

@@ -1086,14 +1086,16 @@ from tavern.core import run
 
 extra_cfg = {
     "variables": {
-        "key_1": "value":,
+        "key_1": "value",
         "key_2": 123,
     }
 }
 
 success = run("test_server.tavern.yaml", extra_cfg)
 ```
 
+An absolute filepath to a configuration file can also be passed.
+
 This is also how things such as strict key checking is controlled via the
 `run()` function. Extra keyword arguments that are taken by this function:
 

tavern/core.py

@@ -9,6 +9,7 @@
 from contextlib2 import ExitStack
 from box import Box
 
+from tavern.schemas.files import wrapfile
 from .util import exceptions
 from .util.dict_util import format_keys
 from .util.delay import delay
@@ -216,7 +217,7 @@ def run_stage(sessions, stage, tavern_box, test_block_config):
     """Run one stage from the test
 
     Args:
-        sessions (list): List of relevant 'session' objects used for this test
+        sessions (dict): Dictionary of relevant 'session' objects used for this test
         stage (dict): specification of stage to be run
         tavern_box (box.Box): Box object containing format variables to be used
             in test
@@ -278,13 +279,8 @@ def _run_pytest(
             FutureWarning,
         )
 
-    if tavern_global_cfg:
-        global_filename = tavern_global_cfg
-
     pytest_args = pytest_args or []
     pytest_args += [in_file]
-    if tavern_global_cfg:
-        pytest_args += ["--tavern-global-cfg", global_filename]
 
     if tavern_mqtt_backend:
         pytest_args += ["--tavern-mqtt-backend", tavern_mqtt_backend]
@@ -293,7 +289,49 @@ def _run_pytest(
     if tavern_strict:
         pytest_args += ["--tavern-strict", tavern_strict]
 
-    return pytest.main(args=pytest_args)
+    with ExitStack() as stack:
+        if tavern_global_cfg:
+            global_filename = _get_or_wrap_global_cfg(stack, tavern_global_cfg)
+            pytest_args += ["--tavern-global-cfg", global_filename]
+
+        return pytest.main(args=pytest_args)
+
+
+def _get_or_wrap_global_cfg(stack, tavern_global_cfg):
+    """
+    Try to parse global configuration from given argument.
+
+    Args:
+        stack (ExitStack): context stack for wrapping file if a dictionary is given
+        tavern_global_cfg (dict, str): Dictionary or string. It should be a
+            path to a file or a dictionary with configuration.
+
+    Returns:
+        str: path to global config file
+
+    Raises:
+        InvalidSettingsError: If global config was not of the right type or a given path
+            does not exist
+
+    Todo:
+        Once python 2 is dropped, allow this to take a 'path like object'
+    """
+    if isinstance(tavern_global_cfg, str):
+        if not os.path.exists(tavern_global_cfg):
+            raise exceptions.InvalidSettingsError(
+                "global config file '{}' does not exist".format(tavern_global_cfg)
+            )
+        global_filename = tavern_global_cfg
+    elif isinstance(tavern_global_cfg, dict):
+        global_filename = stack.enter_context(wrapfile(tavern_global_cfg))
+    else:
+        raise exceptions.InvalidSettingsError(
+            "Invalid format for global settings - must be dict or path to settings file, was {}".format(
+                type(tavern_global_cfg)
+            )
+        )
+
+    return global_filename
 
 
 def run(in_file, tavern_global_cfg=None, **kwargs):

tavern/util/exceptions.py

@@ -91,3 +91,7 @@ class InvalidStageReferenceError(TavernException):
 
 class DuplicateStageDefinitionError(TavernException):
     """Stage with the specified ID previously defined"""
+
+
+class InvalidSettingsError(TavernException):
+    """Configuration was passed incorrectly in some fashion"""

tests/unit/test_call_run.py

@@ -0,0 +1,12 @@
+from tavern.core import run
+
+
+class TestBasicRun:
+    def test_run(self):
+        run("")
+
+    def test_run_with_empty_cfg(self):
+        run("", {})
+
+    def test_run_with_cfg(self):
+        run("", {"a": 2})