systemd: improve dbus type guessingHEADmain

The PIDs property receives integers. Since the guessing code did not
handle integers, it would fail immediately.

1 files changed, 47 insertions, 6 deletions

diff --git a/linuxnamespaces/systemd/__init__.py b/linuxnamespaces/systemd/__init__.py
index d8e7f86..84cb135 100644
--- a/linuxnamespaces/systemd/__init__.py
+++ b/linuxnamespaces/systemd/__init__.py
@@ -8,6 +8,48 @@ import sys
 import typing
 
 
+_DBUS_INTEGER_BOUNDS = (
+    ("q", 0, 1 << 16),
+    ("n", -(1 << 15), 1 << 15),
+    ("u", 0, 1 << 32),
+    ("i", -(1 << 31), 1 << 31),
+    ("t", 0, 1 << 64),
+    ("x", -(1 << 63), 1 << 63),
+)
+
+
+def _guess_dbus_type(value: typing.Any) -> typing.Iterator[str]:
+    """Guess the type of a Python value in dbus. May yield multiple candidates.
+    """
+    if isinstance(value, bool):
+        yield "b"
+    elif isinstance(value, str):
+        yield "s"
+    elif isinstance(value, int):
+        found = False
+        for guess, low, high in _DBUS_INTEGER_BOUNDS:
+            if low <= value < high:
+                found = True
+                yield guess
+        if not found:
+            raise ValueError("integer out of bounds for dbus")
+    elif isinstance(value, float):
+        yield "d"
+    elif isinstance(value, list):
+        if not value:
+            raise ValueError("cannot guess dbus type for empty list")
+        types = [list(_guess_dbus_type(v)) for v in value]
+        found = False
+        for guess in types[0]:
+            if all(guess in guesses for guesses in types):
+                found = True
+                yield "a" + guess
+        if not found:
+            raise ValueError("could not determine homogeneous type of list")
+    else:
+        raise ValueError("failed to guess dbus type")
+
+
 async def start_transient_unit(
     unitname: str,
     pids: list[int] | None = None,
@@ -20,14 +62,13 @@ async def start_transient_unit(
         pids = [os.getpid()]
     dbus_properties.append(("PIDs", ("au", pids)))
     for key, value in ({} if properties is None else properties).items():
-        if isinstance(value, bool):
-            dbus_properties.append((key, ("b", value)))
-        elif isinstance(value, str):
-            dbus_properties.append((key, ("s", value)))
-        else:
+        try:
+            guess = next(_guess_dbus_type(value))
+        except ValueError as err:
             raise ValueError(
                 f"cannot infer dbus type for property {key} value"
-            )
+            ) from err
+        dbus_properties.append((key, (guess, value)))
     if dbusdriver in ("auto", "jeepney"):
         try:
             from .jeepney import start_transient_unit as jeepney_impl