Merge pull request #12483 from DeterminateSystems/json-logger

JSONLogger: Log to a file descriptor instead of another Logger

src/build-remote/build-remote.cc

@@ -51,7 +51,7 @@ static bool allSupportedLocally(Store & store, const std::set<std::string>& requ
 static int main_build_remote(int argc, char * * argv)
 {
     {
-        logger = makeJSONLogger(*logger);
+        logger = makeJSONLogger(getStandardError());
 
         /* Ensure we don't get any SSH passphrase or host key popups. */
         unsetenv("DISPLAY");

src/libmain/loggers.cc

@@ -27,7 +27,7 @@ Logger * makeDefaultLogger() {
     case LogFormat::rawWithLogs:
         return makeSimpleLogger(true);
     case LogFormat::internalJSON:
-        return makeJSONLogger(*makeSimpleLogger(true));
+        return makeJSONLogger(getStandardError());
     case LogFormat::bar:
         return makeProgressBar();
     case LogFormat::barWithLogs: {

src/libstore/unix/build/local-derivation-goal.cc

@@ -2225,7 +2225,7 @@ void LocalDerivationGoal::runChild()
         /* Execute the program.  This should not return. */
         if (drv->isBuiltin()) {
             try {
-                logger = makeJSONLogger(*logger);
+                logger = makeJSONLogger(getStandardError());
 
                 std::map<std::string, Path> outputs;
                 for (auto & e : drv->outputs)

src/libutil/logging.cc

@@ -167,9 +167,9 @@ void to_json(nlohmann::json & json, std::shared_ptr<Pos> pos)
 }
 
 struct JSONLogger : Logger {
-    Logger & prevLogger;
+    Descriptor fd;
 
-    JSONLogger(Logger & prevLogger) : prevLogger(prevLogger) { }
+    JSONLogger(Descriptor fd) : fd(fd) { }
 
     bool isVerbose() override {
         return true;
@@ -190,7 +190,7 @@ struct JSONLogger : Logger {
 
     void write(const nlohmann::json & json)
     {
-        prevLogger.log(lvlError, "@nix " + json.dump(-1, ' ', false, nlohmann::json::error_handler_t::replace));
+        writeLine(fd, "@nix " + json.dump(-1, ' ', false, nlohmann::json::error_handler_t::replace));
     }
 
     void log(Verbosity lvl, std::string_view s) override
@@ -262,9 +262,9 @@ struct JSONLogger : Logger {
     }
 };
 
-Logger * makeJSONLogger(Logger & prevLogger)
+Logger * makeJSONLogger(Descriptor fd)
 {
-    return new JSONLogger(prevLogger);
+    return new JSONLogger(fd);
 }
 
 static Logger::Fields getFields(nlohmann::json & json)

src/libutil/logging.hh

@@ -3,6 +3,7 @@
 
 #include "error.hh"
 #include "config.hh"
+#include "file-descriptor.hh"
 
 #include <nlohmann/json_fwd.hpp>
 
@@ -183,7 +184,7 @@ extern Logger * logger;
 
 Logger * makeSimpleLogger(bool printBuildLogs = true);
 
-Logger * makeJSONLogger(Logger & prevLogger);
+Logger * makeJSONLogger(Descriptor fd);
 
 /**
  * @param source A noun phrase describing the source of the message, e.g. "the builder".