Improve file errors handling

docs/releasenotes/unreleased/fixes.1.rst

@@ -0,0 +1,12 @@
+Improved error handling of file related issues (#629)
+-----------------------------------------------------
+
+In case Robotidy failed to read or write to file, generic message with decode error was shown. Now it will display
+more detailed error message::
+
+    > robotidy read_only_file.robot
+    Failed to decode read_only_file.robot with an error: Opening file 'read_only_file.robot' failed:
+    PermissionError: [Errno 13] Permission denied: 'read_only_file.robot'
+    Skipping file
+
+    0 files reformatted, 1 file left unchanged.

robotidy/app.py

@@ -50,19 +50,15 @@ def transform_files(self):
                 if disabler_finder.file_disabled:
                     continue
                 diff, old_model, new_model, model = self.transform_until_stable(model, disabler_finder)
-                if diff:
-                    self.log_formatted_source(source, stdin)
-                    changed_files += 1
-                self.output_diff(model_path, old_model, new_model)
                 if stdin:
                     self.print_to_stdout(new_model)
                 elif diff:
                     self.save_model(model_path, model)
-            except DataError:
-                click.echo(
-                    f"Failed to decode {source}. Default supported encoding by Robot Framework is UTF-8. Skipping file"
-                )
-                pass
+                    self.log_formatted_source(source, stdin)
+                    self.output_diff(model_path, old_model, new_model)
+                    changed_files += 1
+            except DataError as err:
+                click.echo(f"Failed to decode {source} with an error: {err}\nSkipping file")
         return self.formatting_result(all_files, changed_files, stdin)
 
     def formatting_result(self, all_files: int, changed_files: int, stdin: bool):

tests/utest/test_cli.py

@@ -351,6 +351,12 @@ def test_check_overwrite(self, source, return_status, expected_output):
                 mock_writer.assert_not_called()
             assert result.output == expected_output
 
+    def test_read_only_file(self):
+        source = TEST_DATA_DIR / "read_only" / "test.robot"
+        # overwrite input which is read-only file
+        result = run_tidy([str(source)], overwrite_input=True)
+        assert "Permission denied" in result.output
+
     @pytest.mark.parametrize("color_flag", ["--color", "--no-color", None])
     @pytest.mark.parametrize("color_env", [True, False])
     def test_disable_coloring(self, color_flag, color_env):

tests/utest/testdata/read_only/test.robot

@@ -0,0 +1,10 @@
+*** Settings ***
+
+
+
+
+
+
+*** Test Cases ***
+Test
+    Test

tests/utest/utils.py

@@ -6,14 +6,21 @@
 from robotidy.cli import cli
 
 
-def run_tidy(args: List[str] = None, exit_code: int = 0, output: Optional[str] = None, std_in: Optional = None):
+def run_tidy(
+    args: List[str] = None,
+    exit_code: int = 0,
+    output: Optional[str] = None,
+    std_in: Optional = None,
+    overwrite_input: bool = False,
+):
     runner = CliRunner()
     arguments = args if args is not None else []
-    if output:
-        output_path = str(Path(Path(__file__).parent, "actual", output))
-    else:
-        output_path = str(Path(Path(__file__).parent, "actual", "tmp"))
-    arguments = ["--output", output_path] + arguments
+    if not overwrite_input:
+        if output:
+            output_path = str(Path(Path(__file__).parent, "actual", output))
+        else:
+            output_path = str(Path(Path(__file__).parent, "actual", "tmp"))
+        arguments = ["--output", output_path] + arguments
     result = runner.invoke(cli, arguments, input=std_in)
     if result.exit_code != exit_code:
         print(result.output)