refactor: RAII logger suspension

src/libutil/logging.cc

@@ -43,6 +43,19 @@ void Logger::writeToStdout(std::string_view s)
     writeFull(standard_out, "\n");
 }
 
+Logger::Suspension Logger::suspend()
+{
+    pause();
+    return Suspension { ._finalize = {[this](){this->resume();}} };
+}
+
+std::optional<Logger::Suspension> Logger::suspendIf(bool cond)
+{
+    if (cond)
+        return suspend();
+    return {};
+}
+
 class SimpleLogger : public Logger
 {
 public:

src/libutil/logging.hh

@@ -4,6 +4,7 @@
 #include "error.hh"
 #include "config.hh"
 #include "file-descriptor.hh"
+#include "finally.hh"
 
 #include <nlohmann/json_fwd.hpp>
 
@@ -75,6 +76,17 @@ public:
 
     virtual void stop() { };
 
+    /**
+     * Guard object to resume the logger when done.
+     */
+    struct Suspension {
+        Finally<std::function<void()>> _finalize;
+    };
+
+    Suspension suspend();
+
+    std::optional<Suspension> suspendIf(bool cond);
+
     virtual void pause() { };
     virtual void resume() { };
 

src/libutil/unix/processes.cc

@@ -306,15 +306,7 @@ void runProgram2(const RunOptions & options)
     // case), so we can't use it if we alter the environment
     processOptions.allowVfork = !options.environment;
 
-    std::optional<Finally<std::function<void()>>> resumeLoggerDefer;
-    if (options.isInteractive) {
-        logger->pause();
-        resumeLoggerDefer.emplace(
-            []() {
-                logger->resume();
-            }
-        );
-    }
+    auto suspension = logger->suspendIf(options.isInteractive);
 
     /* Fork. */
     Pid pid = startProcess([&] {

src/libutil/windows/processes.cc

@@ -312,11 +312,7 @@ void runProgram2(const RunOptions & options)
     // TODO: Implement shebang / program interpreter lookup on Windows
     auto interpreter = getProgramInterpreter(realProgram);
 
-    std::optional<Finally<std::function<void()>>> resumeLoggerDefer;
-    if (options.isInteractive) {
-        logger->pause();
-        resumeLoggerDefer.emplace([]() { logger->resume(); });
-    }
+    auto suspension = logger->suspendIf(options.isInteractive);
 
     Pid pid = spawnProcess(interpreter.has_value() ? *interpreter : realProgram, options, out, in);