Add debug tools for SSZ deserialization (#4729)

Author: jtraglia

tests/core/pyspec/eth2spec/debug/tools.py

@@ -0,0 +1,71 @@
+"""
+Helper functions to get SSZ objects from files and output them.
+"""
+
+from pathlib import Path
+from typing import TypeVar
+
+import snappy
+from ruamel.yaml import YAML
+
+from eth2spec.debug.encode import encode
+from eth2spec.utils.ssz.ssz_impl import deserialize
+
+SSZObject = TypeVar("SSZObject")
+
+
+def get_ssz_object_from_ssz_encoded(file_path: Path, typ: SSZObject) -> SSZObject:
+    """
+    Get the SSZObject from an SSZ-encoded file.
+
+    Automatically detects whether the file is snappy-compressed based on the file extension:
+    - .ssz_snappy: snappy-compressed
+    - .ssz: uncompressed
+
+    Args:
+        file_path: Path to the SSZ file (.ssz or .ssz_snappy)
+        typ: The SSZ type to deserialize into
+
+    Returns:
+        The deserialized SSZ object
+
+    Raises:
+        ValueError: If the file extension is not .ssz or .ssz_snappy
+    """
+    with open(file_path, "rb") as f:
+        data = f.read()
+
+    # Determine if snappy-compressed based on file extension
+    if file_path.suffix == ".ssz_snappy" or file_path.name.endswith(".ssz_snappy"):
+        data = snappy.decompress(data)
+    elif file_path.suffix == ".ssz":
+        pass  # No decompression needed
+    else:
+        raise ValueError(
+            f"Unsupported file extension: {file_path.suffix}. Expected .ssz or .ssz_snappy"
+        )
+
+    return deserialize(typ, data)
+
+
+def output_ssz_to_file(
+    output_path: Path, obj: SSZObject, include_hash_tree_roots: bool = False
+) -> None:
+    """
+    Output an SSZ object to a YAML file.
+
+    Args:
+        output_path: Path where to save the YAML file
+        obj: The SSZ object to encode
+        include_hash_tree_roots: Whether to include hash tree roots in the output
+    """
+    yaml = YAML()
+    yaml.default_flow_style = False
+    yaml.indent(mapping=2, sequence=2, offset=0)
+    yaml.width = 4096
+
+    encoded = encode(obj, include_hash_tree_roots)
+
+    output_path.parent.mkdir(parents=True, exist_ok=True)
+    with open(output_path, "w") as f:
+        yaml.dump(encoded, f)