Resolve conflict between inferred and declared CLI options

- Filter out inferred CLI options that conflict with declared ones
- Regression test for this issue
- Fixes issue #233

src/argh/assembling.py

@@ -516,6 +516,16 @@ def _merge_inferred_and_declared_args(
     #
     specs_by_func_arg_name = OrderedDict()
 
+    # eliminate inferred options that conflict with declared ones
+    for inferred in inferred_args:
+        for declared in declared_args:
+            if inferred.func_arg_name == declared.func_arg_name:
+                continue
+            inferred.cli_arg_names = [
+                name for name in inferred.cli_arg_names
+                if name not in declared.cli_arg_names
+            ]
+
     # arguments inferred from function signature
     for parser_add_argument_spec in inferred_args:
         specs_by_func_arg_name[parser_add_argument_spec.func_arg_name] = (

tests/test_regressions.py

@@ -261,3 +261,22 @@ def func(*, list_files=False):
 
     assert run(parser, "").out == "list_files=False\n"
     assert run(parser, "-l").out == "list_files=True\n"
+
+
+def test_regression_issue233():
+    """
+    Issue #233: conflict when short option does not match first letter
+    of long option
+
+    Use case: assigning short names to options
+    """
+
+    @argh.arg("-n", "--user-name")
+    @argh.arg("-N", "--note")
+    def func(*, user_name="world", note=""):
+        return f"hello, {user_name}! {note}"
+
+    parser = DebugArghParser()
+    parser.set_default_command(func)
+
+    assert run(parser, "-n Sam -N Cheers").out == "hello, Sam! Cheers\n"