dropEmptyInitThenConcatStringsSep -> concatStringSep: diagnostics and docs

These are non-critical, so their behavior is ok to change.
Dropping empty items is not needed and usually not expected.

src/build-remote/build-remote.cc

@@ -16,6 +16,7 @@
 #include "serialise.hh"
 #include "build-result.hh"
 #include "store-api.hh"
+#include "strings.hh"
 #include "derivations.hh"
 #include "local-store.hh"
 #include "legacy.hh"
@@ -206,15 +207,15 @@ static int main_build_remote(int argc, char * * argv)
                         error
                             % drvstr
                             % neededSystem
-                            % dropEmptyInitThenConcatStringsSep<StringSet>(", ", requiredFeatures)
+                            % concatStringsSep<StringSet>(", ", requiredFeatures)
                             % machines.size();
 
                         for (auto & m : machines)
                             error
-                                % dropEmptyInitThenConcatStringsSep<StringSet>(", ", m.systemTypes)
+                                % concatStringsSep<StringSet>(", ", m.systemTypes)
                                 % m.maxJobs
-                                % dropEmptyInitThenConcatStringsSep<StringSet>(", ", m.supportedFeatures)
-                                % dropEmptyInitThenConcatStringsSep<StringSet>(", ", m.mandatoryFeatures);
+                                % concatStringsSep<StringSet>(", ", m.supportedFeatures)
+                                % concatStringsSep<StringSet>(", ", m.mandatoryFeatures);
 
                         printMsg(couldBuildLocally ? lvlChatty : lvlWarn, error.str());
 

src/libcmd/command.cc

@@ -1,3 +1,5 @@
+#include <nlohmann/json.hpp>
+
 #include "command.hh"
 #include "markdown.hh"
 #include "store-api.hh"
@@ -6,8 +8,7 @@
 #include "nixexpr.hh"
 #include "profiles.hh"
 #include "repl.hh"
-
-#include <nlohmann/json.hpp>
+#include "strings.hh"
 
 extern char * * environ __attribute__((weak));
 
@@ -42,7 +43,7 @@ void NixMultiCommand::run()
         for (auto & [name, _] : commands)
             subCommandTextLines.insert(fmt("- `%s`", name));
         std::string markdownError = fmt("`nix %s` requires a sub-command. Available sub-commands:\n\n%s\n",
-                commandName, dropEmptyInitThenConcatStringsSep("\n", subCommandTextLines));
+                commandName, concatStringsSep("\n", subCommandTextLines));
         throw UsageError(renderMarkdownToTerminal(markdownError));
     }
     command->second->run();

src/libcmd/installables.cc

@@ -27,6 +27,8 @@
 
 #include <nlohmann/json.hpp>
 
+#include "strings-inline.hh"
+
 namespace nix {
 
 void completeFlakeInputPath(
@@ -630,7 +632,7 @@ static void throwBuildErrors(
                 }
                 failedPaths.insert(failedResult->path.to_string(store));
             }
-            throw Error("build of %s failed", dropEmptyInitThenConcatStringsSep(", ", quoteStrings(failedPaths)));
+            throw Error("build of %s failed", concatStringsSep(", ", quoteStrings(failedPaths)));
         }
     }
 }

src/libcmd/repl.cc

@@ -33,6 +33,8 @@
 #include <gc/gc_cpp.h>
 #endif
 
+#include "strings.hh"
+
 namespace nix {
 
 /**
@@ -625,7 +627,7 @@ ProcessLineResult NixRepl::processLine(std::string line)
 
                 markdown +=
                     "**Synopsis:** `builtins." + (std::string) (*doc->name) + "` "
-                    + dropEmptyInitThenConcatStringsSep(" ", args) + "\n\n";
+                    + concatStringsSep(" ", args) + "\n\n";
             }
 
             markdown += stripIndentation(doc->doc);

src/libflake/flake/lockfile.cc

@@ -9,6 +9,8 @@
 #include <iterator>
 #include <nlohmann/json.hpp>
 
+#include "strings.hh"
+
 namespace nix::flake {
 
 static FlakeRef getFlakeRef(
@@ -61,7 +63,7 @@ static std::shared_ptr<Node> doFind(const ref<Node>& root, const InputPath & pat
         std::vector<std::string> cycle;
         std::transform(found, visited.cend(), std::back_inserter(cycle), printInputPath);
         cycle.push_back(printInputPath(path));
-        throw Error("follow cycle detected: [%s]", dropEmptyInitThenConcatStringsSep(" -> ", cycle));
+        throw Error("follow cycle detected: [%s]", concatStringsSep(" -> ", cycle));
     }
     visited.push_back(path);
 
@@ -367,7 +369,7 @@ void check();
 
 std::string printInputPath(const InputPath & path)
 {
-    return dropEmptyInitThenConcatStringsSep("/", path);
+    return concatStringsSep("/", path);
 }
 
 }

src/libmain/shared.cc

@@ -23,6 +23,7 @@
 #include <openssl/crypto.h>
 
 #include "exit.hh"
+#include "strings.hh"
 
 namespace nix {
 
@@ -301,11 +302,11 @@ void printVersion(const std::string & programName)
 #endif
         cfg.push_back("signed-caches");
         std::cout << "System type: " << settings.thisSystem << "\n";
-        std::cout << "Additional system types: " << dropEmptyInitThenConcatStringsSep(", ", settings.extraPlatforms.get()) << "\n";
-        std::cout << "Features: " << dropEmptyInitThenConcatStringsSep(", ", cfg) << "\n";
+        std::cout << "Additional system types: " << concatStringsSep(", ", settings.extraPlatforms.get()) << "\n";
+        std::cout << "Features: " << concatStringsSep(", ", cfg) << "\n";
         std::cout << "System configuration file: " << settings.nixConfDir + "/nix.conf" << "\n";
         std::cout << "User configuration files: " <<
-            dropEmptyInitThenConcatStringsSep(":", settings.nixUserConfFiles)
+            concatStringsSep(":", settings.nixUserConfFiles)
             << "\n";
         std::cout << "Store directory: " << settings.nixStore << "\n";
         std::cout << "State directory: " << settings.nixStateDir << "\n";

src/libstore/build/entry-points.cc

@@ -4,6 +4,7 @@
 #  include "derivation-goal.hh"
 #endif
 #include "local-store.hh"
+#include "strings.hh"
 
 namespace nix {
 
@@ -42,7 +43,7 @@ void Store::buildPaths(const std::vector<DerivedPath> & reqs, BuildMode buildMod
         throw std::move(*ex);
     } else if (!failed.empty()) {
         if (ex) logError(ex->info());
-        throw Error(worker.failingExitStatus(), "build of %s failed", dropEmptyInitThenConcatStringsSep(", ", quoteStrings(failed)));
+        throw Error(worker.failingExitStatus(), "build of %s failed", concatStringsSep(", ", quoteStrings(failed)));
     }
 }
 

src/libstore/misc.cc

@@ -10,6 +10,7 @@
 #include "callback.hh"
 #include "closure.hh"
 #include "filetransfer.hh"
+#include "strings.hh"
 
 namespace nix {
 

src/libstore/unix/build/hook-instance.cc

@@ -3,12 +3,13 @@
 #include "hook-instance.hh"
 #include "file-system.hh"
 #include "child.hh"
+#include "strings.hh"
 
 namespace nix {
 
 HookInstance::HookInstance()
 {
-    debug("starting build hook '%s'", dropEmptyInitThenConcatStringsSep(" ", settings.buildHook.get()));
+    debug("starting build hook '%s'", concatStringsSep(" ", settings.buildHook.get()));
 
     auto buildHookArgs = settings.buildHook.get();