Merge pull request #1 from johndoe6345789/copilot/enforce-strict-type-checking

Add strict type checking and annotation enforcement to _freeze_module.py

Programs/_freeze_module.py

@@ -1,4 +1,4 @@
-"""Python implementation of Programs/_freeze_module.c
+"""Python implementation of Programs/_freeze_module.c with strict type checking.
 
 The pure Python implementation uses same functions and arguments as the C
 implementation.
@@ -7,32 +7,156 @@ The generated byte code is slightly different because
 compile() sets the PyCF_SOURCE_IS_UTF8 flag and objects have a
 reference count > 1. Marshal adds the `FLAG_REF` flag and creates a
 reference `hashtable`.
+
+This version enforces strict type checking with runtime validation.
+An exception is thrown if something is not typed correctly.
+All function parameters must have type annotations.
 """
 
+import inspect
 import marshal
 import sys
+from typing import Any, Callable, TextIO, Type, TypeVar
 
-header = "/* Auto-generated by Programs/_freeze_module.py */"
+header: str = "/* Auto-generated by Programs/_freeze_module.py */"
+
+F = TypeVar('F', bound=Callable[..., Any])
 
 
+def strict_types(func: F) -> F:
+    """Decorator that enforces type annotations on all parameters.
+    
+    Raises:
+        TypeError: If any parameter lacks a type annotation
+    """
+    sig = inspect.signature(func)
+    
+    # Check that all parameters have annotations
+    for param_name, param in sig.parameters.items():
+        if param.annotation == inspect.Parameter.empty:
+            raise TypeError(
+                f"Function '{func.__name__}' parameter '{param_name}' "
+                f"must have a type annotation"
+            )
+    
+    # Check that return type is annotated
+    if sig.return_annotation == inspect.Signature.empty:
+        raise TypeError(
+            f"Function '{func.__name__}' must have a return type annotation"
+        )
+    
+    return func
+
+
+def _check_type(value: Any, expected_type: Type, param_name: str) -> None:
+    """Enforce strict type checking at runtime.
+    
+    Args:
+        value: The value to check
+        expected_type: The expected type(s)
+        param_name: Name of the parameter for error messages
+        
+    Raises:
+        TypeError: If the value doesn't match the expected type
+    """
+    if not isinstance(value, expected_type):
+        # Handle types that may not have __name__ attribute
+        type_name = getattr(expected_type, '__name__', str(expected_type))
+        raise TypeError(
+            f"Parameter '{param_name}' must be of type {type_name}, "
+            f"got {type(value).__name__}"
+        )
+
+
+@strict_types
 def read_text(inpath: str) -> bytes:
+    """Read text from a file and return as bytes.
+    
+    Args:
+        inpath: Path to the input file
+        
+    Returns:
+        The file contents as bytes
+        
+    Raises:
+        TypeError: If inpath is not a string
+    """
+    _check_type(inpath, str, "inpath")
+    
     with open(inpath, "rb") as f:
-        return f.read()
+        result: bytes = f.read()
+    
+    return result
 
 
+@strict_types
 def compile_and_marshal(name: str, text: bytes) -> bytes:
-    filename = f"<frozen {name}>"
+    """Compile Python source code and marshal it.
+    
+    Args:
+        name: Name identifier for the frozen module
+        text: Python source code as bytes
+        
+    Returns:
+        Marshalled bytecode
+        
+    Raises:
+        TypeError: If parameters are not of correct types
+    """
+    _check_type(name, str, "name")
+    _check_type(text, bytes, "text")
+    
+    filename: str = f"<frozen {name}>"
     # exec == Py_file_input
     code = compile(text, filename, "exec", optimize=0, dont_inherit=True)
-    return marshal.dumps(code)
+    result: bytes = marshal.dumps(code)
+    
+    return result
 
 
+@strict_types
 def get_varname(name: str, prefix: str) -> str:
-    return f"{prefix}{name.replace('.', '_')}"
+    """Generate a C variable name from a module name.
+    
+    Args:
+        name: Module name
+        prefix: Prefix for the variable name
+        
+    Returns:
+        C-compatible variable name
+        
+    Raises:
+        TypeError: If parameters are not strings
+    """
+    _check_type(name, str, "name")
+    _check_type(prefix, str, "prefix")
+    
+    result: str = f"{prefix}{name.replace('.', '_')}"
+    return result
 
 
-def write_code(outfile, marshalled: bytes, varname: str) -> None:
-    data_size = len(marshalled)
+@strict_types
+def write_code(outfile: TextIO, marshalled: bytes, varname: str) -> None:
+    """Write marshalled code as C array to output file.
+    
+    Args:
+        outfile: Output file object
+        marshalled: Marshalled bytecode
+        varname: C variable name for the array
+        
+    Raises:
+        TypeError: If parameters are not of correct types
+    """
+    _check_type(marshalled, bytes, "marshalled")
+    _check_type(varname, str, "varname")
+    
+    # Check that outfile has a write method (duck typing for file-like objects)
+    if not hasattr(outfile, 'write') or not callable(getattr(outfile, 'write')):
+        raise TypeError(
+            f"Parameter 'outfile' must be a file-like object with write() method"
+        )
+    
+    data_size: int = len(marshalled)
 
     outfile.write(f"const unsigned char {varname}[] = {{\n")
 
@@ -43,24 +167,50 @@ def write_code(outfile, marshalled: bytes, varname: str) -> None:
     outfile.write("};\n")
 
 
+@strict_types
 def write_frozen(outpath: str, inpath: str, name: str, marshalled: bytes) -> None:
+    """Write frozen module to output file.
+    
+    Args:
+        outpath: Path to output file
+        inpath: Path to input file (unused but kept for API compatibility)
+        name: Module name
+        marshalled: Marshalled bytecode
+        
+    Raises:
+        TypeError: If parameters are not of correct types
+    """
+    _check_type(outpath, str, "outpath")
+    _check_type(inpath, str, "inpath")
+    _check_type(name, str, "name")
+    _check_type(marshalled, bytes, "marshalled")
+    
     with open(outpath, "w") as outfile:
         outfile.write(header)
         outfile.write("\n")
-        arrayname = get_varname(name, "_Py_M__")
+        arrayname: str = get_varname(name, "_Py_M__")
         write_code(outfile, marshalled, arrayname)
 
 
-def main():
+@strict_types
+def main() -> None:
+    """Main entry point for the freeze_module program.
+    
+    Validates command-line arguments and processes the module freezing.
+    
+    Raises:
+        SystemExit: If incorrect number of arguments provided
+        TypeError: If any type validation fails
+    """
     if len(sys.argv) != 4:
         sys.exit("need to specify the name, input and output paths\n")
 
-    name = sys.argv[1]
-    inpath = sys.argv[2]
-    outpath = sys.argv[3]
+    name: str = sys.argv[1]
+    inpath: str = sys.argv[2]
+    outpath: str = sys.argv[3]
 
-    text = read_text(inpath)
-    marshalled = compile_and_marshal(name, text)
+    text: bytes = read_text(inpath)
+    marshalled: bytes = compile_and_marshal(name, text)
     write_frozen(outpath, inpath, name, marshalled)