Broaden safe read text caught exception scope (#3705)

## Changes
Broaden safe read text exception scope to be more safe when reading a
text file. Also the tests are extended.

### Linked issues

Relates to #3703
Relates to #3704

### Functionality

- [x] Changes in the code linting parts

### Tests

- [x] added unit tests

Author: JCZuurmond

src/databricks/labs/ucx/source_code/base.py

@@ -408,7 +408,7 @@ def safe_read_text(path: Path, size: int = -1) -> str | None:
     """
     try:
         return read_text(path, size=size)
-    except (FileNotFoundError, UnicodeDecodeError, PermissionError) as e:
+    except (OSError, UnicodeError) as e:
         logger.warning(f"Could not read file: {path}", exc_info=e)
         return None
 

tests/unit/source_code/test_base.py

@@ -16,6 +16,7 @@
     back_up_path,
     revert_back_up_path,
     safe_write_text,
+    safe_read_text,
     write_text,
 )
 from databricks.labs.ucx.source_code.linters.base import Fixer
@@ -109,6 +110,46 @@ def apply(self, code) -> str:
     assert not fixer.is_supported("other-code")
 
 
+def test_safe_read_text(tmp_path) -> None:
+    """Should read the contents of a file."""
+    path = tmp_path / "file.txt"
+    path.write_text("contents")
+
+    contents = safe_read_text(path)
+
+    assert contents == "contents"
+
+
+def test_safe_read_text_handles_non_existing_file() -> None:
+    """Should return None when the file does not exist."""
+    contents = safe_read_text(Path("non-existing-file.txt"))
+    assert contents is None
+
+
+def test_safe_read_text_handles_directory(tmp_path) -> None:
+    """Should return None when the path is a directory."""
+    contents = safe_read_text(tmp_path)
+    assert contents is None
+
+
+@pytest.mark.parametrize(
+    "os_error",
+    [
+        PermissionError("Permission denied"),
+        FileNotFoundError("File not found"),
+        UnicodeDecodeError("utf-8", b"\x80\x81\x82", 0, 1, "invalid start byte"),
+    ],
+)
+def test_safe_read_text_handles_os_errors(os_error: OSError) -> None:
+    """Should return None when an OSError occurs."""
+    path = create_autospec(Path)
+    path.open.side_effect = os_error
+
+    contents = safe_read_text(path)
+
+    assert contents is None
+
+
 def test_write_text_to_non_existing_file(tmp_path) -> None:
     path = tmp_path / "file.txt"