Add channel-aware release tooling and updater recovery

ptlinux/system_identity.py

@@ -0,0 +1,83 @@
+"""Identify the host OS without losing the launcher's execution runtime."""
+
+from __future__ import annotations
+
+from dataclasses import dataclass
+from pathlib import Path
+import re
+
+
+EXECUTION_OS_RELEASE = Path("/etc/os-release")
+CONTAINER_HOST_OS_RELEASE = Path("/run/host/os-release")
+STEAM_RUNTIME_OS_ID = "steamrt"
+
+
+@dataclass(frozen=True)
+class SystemIdentity:
+	"""OS releases visible to the launcher process and its container host."""
+
+	execution_release: dict[str, str]
+	host_release: dict[str, str] | None
+
+	@property
+	def operating_system_release(self) -> dict[str, str]:
+		return self.host_release or self.execution_release
+
+	@property
+	def running_inside_steam_runtime(self) -> bool:
+		return (
+			self.execution_release.get("ID", "").strip().casefold()
+			== STEAM_RUNTIME_OS_ID
+		)
+
+
+def detect_system_identity(
+	*,
+	execution_os_release: Path = EXECUTION_OS_RELEASE,
+	host_os_release: Path = CONTAINER_HOST_OS_RELEASE,
+) -> SystemIdentity:
+	"""Read the runtime OS and the standard container-host identity, if present."""
+
+	execution = read_os_release(execution_os_release)
+	host: dict[str, str] | None = None
+	if execution.get("ID", "").strip().casefold() == STEAM_RUNTIME_OS_ID:
+		candidate = read_os_release(host_os_release)
+		candidate_id = candidate.get("ID", "").strip().casefold()
+		if candidate_id and candidate_id != STEAM_RUNTIME_OS_ID:
+			host = candidate
+	return SystemIdentity(execution_release=execution, host_release=host)
+
+
+def detect_distribution_id() -> str:
+	"""Return the host distribution ID when a container exposes it."""
+
+	release = detect_system_identity().operating_system_release
+	return release.get("ID", "").strip().casefold()
+
+
+def is_running_inside_steam_runtime() -> bool:
+	"""Return whether the launcher process itself is inside Steam Runtime."""
+
+	return detect_system_identity().running_inside_steam_runtime
+
+
+def read_os_release(path: Path) -> dict[str, str]:
+	"""Read bounded freedesktop os-release fields without invoking host tools."""
+
+	try:
+		lines = path.read_text(encoding="utf-8", errors="replace").splitlines()
+	except OSError:
+		return {}
+	result: dict[str, str] = {}
+	for line in lines:
+		if not line or line.startswith("#") or "=" not in line:
+			continue
+		key, raw = line.split("=", 1)
+		if not re.fullmatch(r"[A-Z][A-Z0-9_]*", key):
+			continue
+		value = raw.strip()
+		if len(value) >= 2 and value[0] == value[-1] and value[0] in {"'", '"'}:
+			value = value[1:-1]
+		value = value.replace(r"\n", " ").replace(r"\"", '"').replace(r"\\", "\\")
+		result[key] = value[:255]
+	return result