From 58b113d62332bb221b080af5c6d941fe5511e96f Mon Sep 17 00:00:00 2001
From: eldritch horrors <pennae@lix.systems>
Date: Mon, 17 Mar 2025 15:45:27 +0100
Subject: [PATCH] libutil: make RunningProgram more useful

make it moveable, make it killable, and add a stdout fd accessor.

Change-Id: I2387cbe8ac67b899a322cd6c7d306ef9ea7abcd0
---
 lix/libcmd/repl.cc                    |  4 ++--
 lix/libfetchers/git.cc                |  2 +-
 lix/libstore/build/derivation-goal.cc |  2 +-
 lix/libutil/processes.cc              | 19 +++++++++++++++++--
 lix/libutil/processes.hh              | 16 +++++++++++++++-
 5 files changed, 36 insertions(+), 7 deletions(-)

diff --git a/lix/libcmd/repl.cc b/lix/libcmd/repl.cc
index ae10e8eb4..2b5cfc866 100644
--- a/lix/libcmd/repl.cc
+++ b/lix/libcmd/repl.cc
@@ -254,7 +254,7 @@ void runNix(Path program, const Strings & args)
         .program = settings.nixBinDir+ "/" + program,
         .args = args,
         .environment = subprocessEnv,
-    }).wait();
+    }).waitAndCheck();
 
     return;
 }
@@ -672,7 +672,7 @@ ProcessLineResult NixRepl::processLine(std::string line)
 
         // runProgram redirects stdout to a StringSink,
         // using runProgram2 to allow editors to display their UI
-        runProgram2(RunOptions { .program = editor, .searchPath = true, .args = args }).wait();
+        runProgram2(RunOptions { .program = editor, .searchPath = true, .args = args }).waitAndCheck();
 
         // Reload right after exiting the editor if path is not in store
         // Store is immutable, so there could be no changes, so there's no need to reload
diff --git a/lix/libfetchers/git.cc b/lix/libfetchers/git.cc
index 21fa1904d..462be82ab 100644
--- a/lix/libfetchers/git.cc
+++ b/lix/libfetchers/git.cc
@@ -766,7 +766,7 @@ struct GitInputScheme : InputScheme
                 .args = { "-C", repoDir, "--git-dir", gitDir, "archive", input.getRev()->gitRev() },
                 .captureStdout = true,
             });
-            Finally const _wait([&] { proc.wait(); });
+            Finally const _wait([&] { proc.waitAndCheck(); });
 
             unpackTarfile(*proc.getStdout(), tmpDir);
         }
diff --git a/lix/libstore/build/derivation-goal.cc b/lix/libstore/build/derivation-goal.cc
index f96cec1ed..c6c971709 100644
--- a/lix/libstore/build/derivation-goal.cc
+++ b/lix/libstore/build/derivation-goal.cc
@@ -1015,7 +1015,7 @@ void runPostBuildHook(
     });
     Finally const _wait([&] {
         try {
-            proc.wait();
+            proc.waitAndCheck();
         } catch (nix::Error & e) {
             e.addTrace(nullptr,
                 "while running the post-build-hook %s for derivation %s",
diff --git a/lix/libutil/processes.cc b/lix/libutil/processes.cc
index e2cc2515b..6b24d943f 100644
--- a/lix/libutil/processes.cc
+++ b/lix/libutil/processes.cc
@@ -249,7 +249,7 @@ std::pair<int, std::string> runProgram(RunOptions && options)
 
     try {
         auto proc = runProgram2(options);
-        Finally const _wait([&] { proc.wait(); });
+        Finally const _wait([&] { proc.waitAndCheck(); });
         stdout = proc.getStdout()->drain();
     } catch (ExecError & e) {
         status = e.status;
@@ -277,7 +277,22 @@ RunningProgram::~RunningProgram()
     }
 }
 
-void RunningProgram::wait()
+std::tuple<pid_t, std::unique_ptr<Source>, int> RunningProgram::release()
+{
+    return {pid.release(), std::move(stdoutSource), stdout_.release()};
+}
+
+int RunningProgram::kill()
+{
+    return pid.kill();
+}
+
+int RunningProgram::wait()
+{
+    return pid.wait();
+}
+
+void RunningProgram::waitAndCheck()
 {
     if (std::uncaught_exceptions() == 0) {
         int status = pid.wait();
diff --git a/lix/libutil/processes.hh b/lix/libutil/processes.hh
index e9e4eb15a..01c42b9fc 100644
--- a/lix/libutil/processes.hh
+++ b/lix/libutil/processes.hh
@@ -102,9 +102,23 @@ private:
 
 public:
     RunningProgram() = default;
+    RunningProgram(RunningProgram &&) = default;
+    RunningProgram & operator=(RunningProgram &&) = default;
     ~RunningProgram();
 
-    void wait();
+    explicit operator bool() const { return bool(pid); }
+
+    std::tuple<pid_t, std::unique_ptr<Source>, int> release();
+
+    int kill();
+    [[nodiscard]]
+    int wait();
+    void waitAndCheck();
+
+    std::optional<int> getStdoutFD() const
+    {
+        return stdout_ ? std::optional(stdout_.get()) : std::nullopt;
+    }
 
     Source * getStdout() const { return stdoutSource.get(); };
 };