fixes for linting modules without an input

nf_core/components/nfcore_component.py

@@ -184,6 +184,7 @@ def get_inputs_from_main_nf(self) -> None:
         # don't match anything inside comments or after "output:"
         if "input:" not in data:
             log.debug(f"Could not find any inputs in {self.main_nf}")
+            return
         input_data = data.split("input:")[1].split("output:")[0]
         for line in input_data.split("\n"):
             channel_elements: list[dict[str, dict[str, str]]] = []

nf_core/modules/lint/__init__.py

@@ -288,7 +288,7 @@ def update_meta_yml_file(self, mod):
         if "output" in meta_yml:
             correct_outputs, meta_outputs = self.obtain_correct_and_specified_outputs(mod, meta_yml)
 
-        if correct_inputs != meta_inputs:
+        if "input" in meta_yml and correct_inputs != meta_inputs:
             log.debug(
                 f"Correct inputs: '{correct_inputs}' differ from current inputs: '{meta_inputs}' in '{mod.meta_yml}'"
             )
@@ -319,7 +319,7 @@ def update_meta_yml_file(self, mod):
                                             ][feature]
                                     break
 
-        if correct_outputs != meta_outputs:
+        if "output" in meta_yml and correct_outputs != meta_outputs:
             log.debug(
                 f"Correct outputs: '{correct_outputs}' differ from current outputs: '{meta_outputs}' in '{mod.meta_yml}'"
             )