Port upstream PR #2341: -i "" launches portable instance

Distinguish between -i (no value, prints current instance and exits)
and -i "" (launches the portable instance if one exists) by switching
the option parser from std::string to boost::optional<std::string>.

Cherry-picked from upstream 49da80c.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

1 files changed, 19 insertions, 5 deletions

diff --git a/src/src/commandline.cpp b/src/src/commandline.cpp
index 4ff408e..46f9be0 100644
--- a/src/src/commandline.cpp
+++ b/src/src/commandline.cpp
@@ -13,6 +13,7 @@
 #include <QFile>
 #include <QSettings>
 #include <QTextStream>
+#include <boost/optional/optional_io.hpp>
 
 namespace cl
 {
@@ -233,8 +234,12 @@ std::optional<int> CommandLine::runEarly()
 
 std::optional<int> CommandLine::runPostApplication(MOApplication& a)
 {
-  // handle -i with no arguments
-  if (m_vm.contains("instance") && m_vm["instance"].as<std::string>().empty()) {
+  const auto instanceArg = m_vm.find("instance");
+  if (instanceArg != m_vm.end() &&
+      !instanceArg->second.as<boost::optional<std::string>>().has_value()) {
+    // handle -i with no arguments (distinct from -i "", which will launch the
+    // portable instance if it exists, hence the use of boost::optional).
+    // Upstream PR #2341.
     env::Console const c;
 
     if (auto i = InstanceManager::singleton().currentInstance()) {
@@ -326,7 +331,9 @@ void CommandLine::createOptions()
 
               ("logs", "duplicates the logs to stdout")
 
-                  ("instance,i", po::value<std::string>()->implicit_value(""),
+                  ("instance,i",
+                   po::value<boost::optional<std::string>>()->implicit_value(
+                       boost::none),
                    "use the given instance (defaults to last used)")
 
                       ("profile,p", po::value<std::string>(),
@@ -414,8 +421,15 @@ std::optional<QString> CommandLine::instance() const
 
   if (m_shortcut.isValid() && m_shortcut.hasInstance()) {
     return m_shortcut.instanceName();
-  } else if (m_vm.contains("instance")) {
-    return QString::fromStdString(m_vm["instance"].as<std::string>());
+  } else {
+    const auto instanceArg = m_vm.find("instance");
+    if (instanceArg != m_vm.end()) {
+      const auto& instanceVal =
+          instanceArg->second.as<boost::optional<std::string>>();
+      if (instanceVal.has_value()) {
+        return QString::fromStdString(instanceVal.value());
+      }
+    }
   }
 
   return {};