Use pydantic to validate config

We can use pydantic to ensure that the expected config values are present. This
is an improvement over the existing use of 'assert' statements.

Also adds some unit tests for the new validation.

src/bugjira/config.py

@@ -1,6 +1,30 @@
 import json
 
-from pydantic import BaseModel, validator
+from pydantic import BaseModel, validator, constr
+
+
+class BugzillaConfig(BaseModel):
+    URL: constr(strip_whitespace=True, min_length=1)
+    api_key: constr(strip_whitespace=True, min_length=1)
+
+    class Config:
+        extra = 'forbid'
+
+
+class JiraConfig(BaseModel):
+    URL: constr(strip_whitespace=True, min_length=1)
+    token_auth: constr(strip_whitespace=True, min_length=1)
+
+    class Config:
+        extra = 'forbid'
+
+
+class ConfigDict(BaseModel):
+    bugzilla: BugzillaConfig
+    jira: JiraConfig
+
+    class Config:
+        extra = 'forbid'
 
 
 class Config(BaseModel):
@@ -10,12 +34,7 @@ class Config(BaseModel):
 
     @validator("config_dict")
     def validate_minimum_config(cls, v):
-        assert v.get("bugzilla")
-        assert v.get("bugzilla").get("URL")
-        assert v.get("bugzilla").get("api_key")
-        assert v.get("jira")
-        assert v.get("jira").get("URL")
-        assert v.get("jira").get("token_auth")
+        ConfigDict(**v)
         return v
 
     @staticmethod

tests/unit/test_config.py

@@ -28,16 +28,112 @@ def test_config_good_dict(good_config_dict):
     assert Config.from_config(config_dict=good_config_dict) == good_config_dict
 
 
-def test_config_missing_values(config_defaults):
+def test_config_extra_top_level_value(good_config_dict):
     """
-    GIVEN a json file containing an incomplete definition of a Bugjira config
+    GIVEN a dict containing a Bugjira config with an extra top-level setting
+    WHEN we call Config.from_config using the dict as the config_dict
+    THEN a ValidationError is raised with the appropriate error message
+    """
+    bad_config = deepcopy(good_config_dict)
+    bad_config["foo"] = "bar"
+
+    with pytest.raises(ValidationError) as excinfo:
+        Config.from_config(config_dict=bad_config)
+
+    assert len(excinfo.value.errors()) == 1
+    error = excinfo.value.errors()[0]
+    assert error.get("loc") == ("config_dict", "foo")
+    assert error.get("msg") == "extra fields not permitted"
+    assert error.get("type") == "value_error.extra"
+
+
+def test_config_extra_bugzilla_value(good_config_dict):
+    """
+    GIVEN a dict containing a Bugjira config with an extra bugzilla setting
+    WHEN we call Config.from_config using the dict as the config_dict
+    THEN a ValidationError is raised with the appropriate error message
+    """
+    bad_config = deepcopy(good_config_dict)
+    bad_config["bugzilla"]["foo"] = "bar"
+
+    with pytest.raises(ValidationError) as excinfo:
+        Config.from_config(config_dict=bad_config)
+
+    assert len(excinfo.value.errors()) == 1
+    error = excinfo.value.errors()[0]
+    assert error.get("loc") == ("config_dict", "bugzilla", "foo")
+    assert error.get("msg") == "extra fields not permitted"
+    assert error.get("type") == "value_error.extra"
+
+
+def test_config_extra_jira_value(good_config_dict):
+    """
+    GIVEN a dict containing a Bugjira config with an extra jira setting
+    WHEN we call Config.from_config using the dict as the config_dict
+    THEN a ValidationError is raised with the appropriate error message
+    """
+    bad_config = deepcopy(good_config_dict)
+    bad_config["jira"]["foo"] = "bar"
+
+    with pytest.raises(ValidationError) as excinfo:
+        Config.from_config(config_dict=bad_config)
+
+    assert len(excinfo.value.errors()) == 1
+    error = excinfo.value.errors()[0]
+    assert error.get("loc") == ("config_dict", "jira", "foo")
+    assert error.get("msg") == "extra fields not permitted"
+    assert error.get("type") == "value_error.extra"
+
+
+def test_config_missing_value(good_config_dict):
+    """
+    GIVEN a dict containing a Bugjira config with one missing key
+    WHEN we call Config.from_config using the dict as the config_dict
+    THEN a ValidationError is raised with the appropriate error message
+    """
+    bad_config = deepcopy(good_config_dict)
+    bad_config["jira"].pop("token_auth")
+    with pytest.raises(ValidationError) as excinfo:
+        Config.from_config(config_dict=bad_config)
+
+    assert len(excinfo.value.errors()) == 1
+    error = excinfo.value.errors()[0]
+    assert error.get("loc") == ("config_dict", "jira", "token_auth")
+    assert error.get("msg") == "field required"
+    assert error.get("type") == "value_error.missing"
+
+
+def test_config_empty_value(good_config_dict):
+    """
+    GIVEN a dict containing a Bugjira config with one empty string value
+    WHEN we call Config.from_config using the dict as the config_dict
+    THEN a ValidationError is raised with the appropriate error message
+    """
+    bad_config = deepcopy(good_config_dict)
+    bad_config["jira"]["token_auth"] = ""
+    with pytest.raises(ValidationError) as excinfo:
+        Config.from_config(config_dict=bad_config)
+
+    assert len(excinfo.value.errors()) == 1
+    error = excinfo.value.errors()[0]
+    assert error.get("ctx").get("limit_value") == 1
+    assert error.get("loc") == ("config_dict", "jira", "token_auth")
+
+
+def test_config_empty_values(config_defaults):
+    """
+    GIVEN a json file containing a a Bugjira config with all empty strings for
+        values
     WHEN we call Config.from_config with the path to the file
-    THEN a ValidationError is raised
+    THEN a ValidationError is raised showing all the values were missing
     """
-    with pytest.raises(ValidationError):
+    with pytest.raises(ValidationError) as excinfo:
         Config.from_config(
             config_path=(config_defaults + "/data/config/missing_config.json")
         )
+    for error in excinfo.value.errors():
+        assert error.get("type") == "value_error.any_str.min_length"
+        assert error.get("ctx").get("limit_value") == 1
 
 
 def test_config_no_file(config_defaults):