fix #404

* fix #404

src/translators/factory.py

@@ -24,11 +24,21 @@ def lookup_backend(fiware_service: str) -> MaybeString:
     config = cfg_reader.from_env_file(QL_CONFIG_ENV_VAR, defaults={})
     tenant_backend = maybe_string_match(config, 'tenants', fiware_service,
                                         'backend')
-    default_backend = maybe_string_match(config, 'default-backend')
 
-    env_backend = env_reader.read(StrVar(QL_DEFAULT_DB_ENV_VAR, CRATE_BACKEND))
+    return tenant_backend or default_backend()
 
-    return tenant_backend or env_backend or default_backend
+
+def default_backend() -> MaybeString:
+    cfg_reader = YamlReader(log=log().debug)
+    env_reader = EnvReader(log=log().debug)
+
+    config = cfg_reader.from_env_file(QL_CONFIG_ENV_VAR, defaults={})
+
+    config_backend = maybe_string_match(config, 'default-backend')
+
+    env_backend = env_reader.read(StrVar(QL_DEFAULT_DB_ENV_VAR, None))
+
+    return env_backend or config_backend or CRATE_BACKEND
 
 
 def translator_for(fiware_service: str):

src/translators/tests/ql-config-timescale-default.yml

@@ -0,0 +1,8 @@
+tenants:
+  t1:
+    backend: Timescale
+  t2:
+    backend: Crate
+  T3:
+    backend: Timescale
+default-backend: Timescale

src/translators/tests/test_translator_factory.py

@@ -39,3 +39,13 @@ def test_os_env():
     os.environ['QL_DEFAULT_DB'] = 'crate'
     with translator_for(None) as t:
         assert isinstance(t, CrateTranslator)
+    os.environ['QL_DEFAULT_DB'] = ''
+
+
+def test_fix_404():
+    with translator_for(None) as t:
+        assert isinstance(t, CrateTranslator)
+    os.environ['QL_CONFIG'] = 'src/translators/tests/ql-config-timescale-default.yml'
+    with translator_for(None) as t:
+        assert isinstance(t, PostgresTranslator)
+