Load app metadata from companion app_<target>.json file for Rust binaries

Author: fbeutin-ledger

CHANGELOG.md

@@ -5,6 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [0.15.0] - 2025-12-23
+
+### Added
+
+- Load app metadata from companion app_<target>.json file for rust binaries
+
 ## [0.14.0] - 2025-12-03
 
 ### Added

src/ledgered/binary.py

@@ -1,10 +1,12 @@
+import json
 import logging
 from argparse import ArgumentParser
 from dataclasses import asdict, dataclass
 from elftools.elf.elffile import ELFFile
 from pathlib import Path
 from typing import Optional, Union
 
+from ledgered.devices import Devices
 from ledgered.serializers import Jsonable
 
 LEDGER_PREFIX = "ledger."
@@ -46,10 +48,122 @@ def __init__(self, binary_path: Union[str, Path]):
             }
         self._sections = Sections(**sections)
 
+        # Rust apps store app_name/app_version/app_flags in companion JSON file
+        if self.is_rust_app:
+            self._load_metadata_from_json()
+
+    def _load_metadata_from_json(self) -> None:
+        """Load app metadata from companion app_<target>.json file.
+
+        Rust applications don't embed app_name, app_version, and app_flags in the ELF.
+        Instead, these are stored in a JSON file named app_<target>.json in the same directory.
+        This method is called only for Rust applications.
+
+        Note: The target name in the ELF may differ from the JSON filename.
+        For example, nanos2 -> nanosplus, nanos+ -> nanosplus.
+        """
+        target = self._sections.target
+        if not target:
+            logging.warning(
+                "Rust app detected but no target found, cannot locate companion JSON file"
+            )
+            return
+
+        # Try multiple naming patterns to find the JSON file
+        json_path = self._find_json_file(target)
+        if not json_path:
+            logging.warning(
+                "Rust app detected but companion JSON file not found for target '%s' in %s",
+                target,
+                self._path.parent,
+            )
+            return
+
+        try:
+            logging.info("Loading Rust app metadata from %s", json_path)
+            with json_path.open("r") as f:
+                data = json.load(f)
+
+            if "name" in data:
+                self._sections.app_name = data["name"]
+                logging.debug("Loaded app_name: %s", self._sections.app_name)
+
+            if "version" in data:
+                self._sections.app_version = data["version"]
+                logging.debug("Loaded app_version: %s", self._sections.app_version)
+
+            if "flags" in data:
+                self._sections.app_flags = data["flags"]
+                logging.debug("Loaded app_flags: %s", self._sections.app_flags)
+
+        except (json.JSONDecodeError, OSError) as e:
+            logging.error("Failed to load companion JSON file %s: %s", json_path, e)
+
+    def _find_json_file(self, target: str) -> Optional[Path]:
+        """Find the companion JSON file using multiple naming patterns.
+
+        Tries different naming conventions:
+        1. Exact target name (e.g., nanos2 -> app_nanos2.json)
+        2. Canonical device name (e.g., nanos2 -> app_nanosp.json)
+        3. All device aliases (e.g., nanos+, nanosplus for NanoS+)
+
+        Args:
+            target: The target name from the ELF binary
+
+        Returns:
+            Path to the JSON file if found, None otherwise
+        """
+        candidates = [target]  # Start with exact target name
+
+        try:
+            device = Devices.get_by_name(target)
+            # Add canonical device name
+            candidates.append(device.name)
+            # Add all known aliases
+            candidates.extend(device.names)
+        except KeyError:
+            logging.debug("Unknown device '%s', trying exact name only", target)
+
+        # Try all candidates
+        for candidate in candidates:
+            json_path = self._path.parent / f"app_{candidate}.json"
+            if json_path.exists():
+                logging.debug("Found JSON file with pattern '%s': %s", candidate, json_path)
+                return json_path
+
+        return None
+
+    def _normalize_target_name(self, target: str) -> str:
+        """Normalize target name to match JSON filename conventions.
+
+        Device names can vary (e.g., nanos2, nanos+, nanosplus all refer to the same device).
+        The JSON files use a canonical naming (nanosplus, flex, stax, etc.).
+
+        Args:
+            target: The target name from the ELF binary
+
+        Returns:
+            The normalized target name for JSON file lookup
+        """
+        try:
+            device = Devices.get_by_name(target)
+            return device.name
+        except KeyError:
+            # If device is unknown, return the original target name
+            logging.debug("Unknown device '%s', using target name as-is", target)
+            return target
+
     @property
     def sections(self) -> Sections:
         return self._sections
 
+    @property
+    def is_rust_app(self) -> bool:
+        """Returns True if this is a Rust application."""
+        return (
+            self._sections.rust_sdk_name is not None or self._sections.rust_sdk_version is not None
+        )
+
 
 def set_parser() -> ArgumentParser:
     parser = ArgumentParser(