fix(docs): reject a directory argument without --json too

packages/skilllint/cli_docs.py

@@ -257,11 +257,11 @@ def sections(
 
     Output is written to stdout.
     """
+    if file_path.exists() and not file_path.is_file():
+        typer.echo(f"Expected a file path: {file_path}", err=True)
+        raise typer.Exit(code=2) from None
     if json_output:
         file_exists = file_path.exists()
-        if file_exists and not file_path.is_file():
-            typer.echo(f"Expected a file path: {file_path}", err=True)
-            raise typer.Exit(code=2) from None
         emit_and_exit(build_sections_response(file_path, list_sections(file_path), file_exists=file_exists))
     table = format_section_index(file_path)
     typer.echo(table)
@@ -285,11 +285,11 @@ def section(
     Exit status:
         1 when the heading is not found.
     """
+    if file_path.exists() and not file_path.is_file():
+        typer.echo(f"Expected a file path: {file_path}", err=True)
+        raise typer.Exit(code=2) from None
     if json_output:
         file_exists = file_path.exists()
-        if file_exists and not file_path.is_file():
-            typer.echo(f"Expected a file path: {file_path}", err=True)
-            raise typer.Exit(code=2) from None
         found = find_section(file_path, heading)
         emit_and_exit(
             build_section_response(file_path, heading, found, file_exists=file_exists),
@@ -322,11 +322,11 @@ def verify(
     Exit status:
         1 when MODIFIED or UNVERIFIABLE.
     """
+    if file_path.exists() and not file_path.is_file():
+        typer.echo(f"Expected a file path: {file_path}", err=True)
+        raise typer.Exit(code=2) from None
     if json_output:
         file_exists = file_path.exists()
-        if file_exists and not file_path.is_file():
-            typer.echo(f"Expected a file path: {file_path}", err=True)
-            raise typer.Exit(code=2) from None
         outcome = verify_integrity(file_path)
         emit_and_exit(
             build_verify_response(outcome, file_exists=file_exists),

packages/skilllint/tests/test_cli_docs.py

@@ -13,6 +13,7 @@
 
 from __future__ import annotations
 
+import operator
 import re
 import subprocess
 import sys
@@ -761,3 +762,17 @@ def test_file_path_forwarded_to_verify_integrity(self, cli_runner: CliRunner, mo
 
         # Assert
         mock_verify.assert_called_once_with(Path(target))
+
+
+@pytest.mark.parametrize("args", [("sections",), ("section", "Usage"), ("verify",)], ids=operator.itemgetter(0))
+def test_directory_argument_is_a_usage_error_without_json(
+    args: tuple[str, ...], cli_runner: CliRunner, tmp_path: Path
+) -> None:
+    """A directory gets the same usage error as under ``--json``, not an ``IsADirectoryError`` traceback (#315)."""
+    # Act
+    result = cli_runner.invoke(plugin_validator.app, ["docs", args[0], str(tmp_path), *args[1:]])
+
+    # Assert
+    assert result.exit_code == 2
+    assert f"Expected a file path: {tmp_path}" in result.stderr
+    assert result.exception is None or isinstance(result.exception, SystemExit)