From a739eb0763d3c56608a9e9974422e48d1133c5fe Mon Sep 17 00:00:00 2001
From: Jan Lindemann <jan@janware.com>
Date: Mon, 15 Jun 2026 07:30:17 +0200
Subject: [PATCH] lib.Result: Initialize with status = None

Define default parameter values for Result's constructor, namely None
for exit status, stdout and stderr.

Instantiating a Result object without parameters signifies "this
object doesn't contain data from a real process's exit event". Up to
now, similar meaning has been hand-crafted by ExecContext's run() and
friends by using an error exit status (1) to make sure it wasn't
mistaken for success. This commit formalizes that into the Result
structure itself, but uses None instead for the exit status.

Controlling default values in Result itself also means that the
Result class gets better awareness of what it contains, and its log
messages and stdin / stdout can be more fitting:

 - If a real process failed, make stdout return at least b''
 - If a real process succeeded, make stdout return at least b''

Returning something from .stdout on success fixes a real bug: An
attempt to access what "rpm -U somepackage.rpm" returns, namely
nothing, raises a bogus exception, because stdout is None.

Signed-off-by: Jan Lindemann <jan@janware.com>
---
 src/python/jw/pkg/lib/ExecContext.py |  8 ++++----
 src/python/jw/pkg/lib/Result.py      | 24 ++++++++++++++++--------
 2 files changed, 20 insertions(+), 12 deletions(-)

diff --git a/src/python/jw/pkg/lib/ExecContext.py b/src/python/jw/pkg/lib/ExecContext.py
index d354cf13..398a5d9a 100644
--- a/src/python/jw/pkg/lib/ExecContext.py
+++ b/src/python/jw/pkg/lib/ExecContext.py
@@ -313,7 +313,7 @@ class ExecContext(Base):
         await self.open()
 
         try:
-            ret = Result(None, None, 1)
+            ret = Result()
             with self.CallContext(
                     self,
                     title = title,
@@ -421,7 +421,7 @@ class ExecContext(Base):
         # be returned by CallContext and is very much allowed
         assert cmd_input is not None, 'Invalid: cmd_input is None'
 
-        ret = Result(None, None, 1)
+        ret = Result()
         with self.CallContext(
                 self,
                 title = title,
@@ -454,7 +454,7 @@ class ExecContext(Base):
     async def _get(
         self, path: str, wd: str | None, throw: bool, verbose: bool | None, title: str
     ) -> Result:
-        ret = Result(None, None, 1)
+        ret = Result()
         if wd is not None:
             path = wd + '/' + path
         with self.CallContext(
@@ -508,7 +508,7 @@ class ExecContext(Base):
         ) -> Result:
             return await self.run(cmd, cmd_input = cmd_input, **kwargs)
 
-        ret = Result(None, None, 1)
+        ret = Result()
         try:
 
             class RemoteCmd(NamedTuple):
diff --git a/src/python/jw/pkg/lib/Result.py b/src/python/jw/pkg/lib/Result.py
index d7353739..7a72ff59 100644
--- a/src/python/jw/pkg/lib/Result.py
+++ b/src/python/jw/pkg/lib/Result.py
@@ -4,9 +4,9 @@ class Result:
 
     def __init__(
         self,
-        stdout: bytes | None,
-        stderr: bytes | None,
-        status: int,
+        stdout: bytes | None = None,
+        stderr: bytes | None = None,
+        status: int | None = None,  # Command has not yet exited
         encoding: str = 'UTF-8',
         strip: bool = True,
         cmd: list[str] | None = None,
@@ -56,10 +56,11 @@ class Result:
 
     def __repr__(self) -> str:
         ret = f'{self.__status}:'
-        if self.status != 0:
-            ret += f' err: {self.stderr_str_or_none}'
-        else:
-            ret += f' out: {self.__stdout_footprint(quote=True)}'
+        if self.__status is not None:
+            if self.status != 0:
+                ret += f' err: {self.stderr_str_or_none}'
+            else:
+                ret += f' out: {self.__stdout_footprint(quote=True)}'
         return ret
 
     @property
@@ -104,7 +105,10 @@ class Result:
             if wd is None:
                 wd = self.__wd
             call = f'"{pretty_cmd(cmd, wd)}" '
-        ret = f'Command {call}has exited with status {self.__status}'
+        ret = (
+            f'Command {call}has not yet exited' if self.__status is None else
+            f'Command {call}has exited with status {self.__status}'
+        )
         call = pretty_cmd(cmd, wd)
         if self.status != 0:
             ret += f' -> stderr="{self.__stderr!r}"'
@@ -125,6 +129,8 @@ class Result:
     @property
     def stdout(self) -> bytes:
         if self.__stdout is None:
+            if self.__status == 0:
+                return b''
             raise Exception(f'Result has no standard output stream: {self.summary}')
         return self.__stdout
 
@@ -143,6 +149,8 @@ class Result:
     @property
     def stderr(self) -> bytes:
         if self.__stderr is None:
+            if isinstance(self.__status, int) and self.__status != 0:
+                return b''
             raise Exception(f'Result has no standard error stream: {self.summary}')
         return self.__stderr
 
-- 
2.54.0