feat(gateway): safe type converter (1879 BUG-1/BUG-2)

ingestor/converters.py

@@ -0,0 +1,42 @@
+"""Safe coercion of JSON-transported values into typed OPC write values.
+
+Fixes 1879 BUG-1 (bool('false') is True in Python) and BUG-2 (uncaught
+TypeError/ValueError from int/float on bad input).
+"""
+
+_FALSE_STRINGS = {'false', '0', 'no', 'off', ''}
+
+
+class ConversionError(ValueError):
+    """Raised when a raw value cannot be coerced to the requested type."""
+
+
+def _to_bool(raw) -> bool:
+    if isinstance(raw, bool):
+        return raw
+    if isinstance(raw, (int, float)):
+        return bool(raw)
+    return str(raw).strip().lower() not in _FALSE_STRINGS
+
+
+def to_typed_value(raw, data_type: str):
+    """Coerce raw (often a JSON string) to the given data_type.
+
+    data_type: 'boolean' | 'int' | 'float' | 'double' | 'string'.
+    Raises ConversionError on any invalid input (never a bare TypeError).
+    """
+    dtype = data_type.strip().lower()
+    try:
+        if dtype in ('bool', 'boolean'):
+            return _to_bool(raw)
+        if dtype in ('int', 'integer'):
+            if isinstance(raw, str) and ('.' in raw or raw.strip() == ''):
+                raise ConversionError(f'invalid int: {raw!r}')
+            return int(raw)
+        if dtype in ('float', 'double', 'real'):
+            return float(raw)
+        if dtype in ('str', 'string'):
+            return str(raw)
+    except (TypeError, ValueError) as e:
+        raise ConversionError(f'cannot convert {raw!r} to {data_type}: {e}') from e
+    raise ConversionError(f'unknown data_type: {data_type!r}')

tests/unit/test_converters.py

@@ -0,0 +1,24 @@
+import pytest
+
+from ingestor.converters import ConversionError, to_typed_value
+
+
+@pytest.mark.parametrize('raw,expected', [
+    ('false', False), ('False', False), ('0', False), ('no', False),
+    ('off', False), ('', False), ('true', True), ('1', True), (True, True),
+])
+def test_bool_from_json_string(raw, expected):
+    assert to_typed_value(raw, 'boolean') is expected
+
+
+def test_float_and_int():
+    assert to_typed_value('42.5', 'float') == 42.5
+    assert to_typed_value('7', 'int') == 7
+
+
+@pytest.mark.parametrize('raw,dtype', [
+    (None, 'int'), ('abc', 'float'), ('123.123', 'int'), (None, 'float'),
+])
+def test_invalid_raises_conversion_error(raw, dtype):
+    with pytest.raises(ConversionError):
+        to_typed_value(raw, dtype)