Make template_render only load gen_kw export if it exists

python/res/fm/templating/template_render.py

@@ -78,7 +78,11 @@ def render_template(input_files, template_file, output_file):
     if isinstance(input_files, str) and input_files:
         input_files = (input_files,)
 
-    all_input_files = (DEFAULT_GEN_KW_EXPORT_NAME + ".json",)
+    all_input_files = ()
+
+    gen_kw_export_path = DEFAULT_GEN_KW_EXPORT_NAME + ".json"
+    if os.path.isfile(gen_kw_export_path):
+        all_input_files += (gen_kw_export_path,)
 
     if input_files:
         all_input_files += tuple(input_files)

tests/res/fm/test_templating.py

@@ -31,6 +31,13 @@ class TemplatingTest(ResTest):
         + "OTH_TEST {{third.key1.subkey1}}"
     )
 
+    mulitple_input_template_no_param = (
+        "FILENAME\n"
+        + "F1 {{not_the_standard_parameters.key1.subkey1}}\n"
+        + "OTH {{second.key1.subkey2}}\n"
+        + "OTH_TEST {{third.key1.subkey1}}"
+    )
+
     default_parameters = {
         "key1": {"subkey1": 1999.22, "subkey2": 200},
         "key2": {"subkey1": 300},
@@ -139,6 +146,38 @@ def test_template_multiple_input(self):
 
             self.assertEqual(parameter_file.read(), expected_output)
 
+    @tmpdir()
+    def test_no_parameters_json(self):
+        with open("template", "w") as template_file:
+            template_file.write(self.mulitple_input_template_no_param)
+
+        with open("not_the_standard_parameters.json", "w") as json_file:
+            json_file.write(json.dumps(self.default_parameters))
+
+        with open("second.json", "w") as json_file:
+            parameters = {"key1": {"subkey2": 1400}}
+            json.dump(parameters, json_file)
+        with open("third.json", "w") as json_file:
+            parameters = {
+                "key1": {
+                    "subkey1": 3000.22,
+                }
+            }
+            json.dump(parameters, json_file)
+
+        render_template(
+            ["second.json", "third.json", "not_the_standard_parameters.json"],
+            "template",
+            "out_file",
+        )
+
+        with open("out_file", "r") as parameter_file:
+            expected_output = (
+                "FILENAME\n" + "F1 1999.22\n" + "OTH 1400\n" + "OTH_TEST 3000.22"
+            )
+
+            self.assertEqual(parameter_file.read(), expected_output)
+
     @tmpdir()
     def test_template_executable(self):
         with TestAreaContext("templating") as tac: