[libcalamares] Refactor Python target_env calls

This is why the whole refactoring started: to get the process output
and exit code in one spot so we can attach the process output
to the (Python exception) CalledProcessError in all the code
paths, not just those that are explicitly looking for output.

src/libcalamares/PythonJobApi.cpp

@@ -37,21 +37,21 @@
 namespace bp = boost::python;
 
 static int
-_handle_check_target_env_call_error( int ec, const QString& cmd, const QString& output = QString() )
+_handle_check_target_env_call_error( const CalamaresUtils::ProcessResult& ec, const QString& cmd )
 {
-    if ( !ec )
-        return ec;
+    if ( !ec.first )
+        return ec.first;
 
     QString raise = QString( "import subprocess\n"
                              "e = subprocess.CalledProcessError(%1,\"%2\")\n" )
-                    .arg( ec )
+                    .arg( ec.first )
                     .arg( cmd );
-    if ( !output.isEmpty() )
-        raise.append( QStringLiteral("e.output = \"\"\"%1\"\"\"\n").arg( output ) );
+    if ( !ec.second.isEmpty() )
+        raise.append( QStringLiteral("e.output = \"\"\"%1\"\"\"\n").arg( ec.second ) );
     raise.append("raise e");
     bp::exec( raise.toStdString().c_str() );
     bp::throw_error_already_set();
-    return ec;
+    return ec.first;
 }
 
 namespace CalamaresPython
@@ -83,29 +83,36 @@ _bp_list_to_qstringlist( const bp::list& args )
     return list;
 }
 
-int
-target_env_call( const std::string& command,
-                 const std::string& stdin,
-                 int timeout )
+static inline CalamaresUtils::ProcessResult
+_target_env_command(
+    const QStringList& args,
+    const std::string& stdin,
+    int timeout )
 {
     return CalamaresUtils::System::instance()->
-           targetEnvCall( QString::fromStdString( command ),
+        targetEnvCommand( args,
                           QString(),
                           QString::fromStdString( stdin ),
                           timeout );
 }
 
+int
+target_env_call( const std::string& command,
+                 const std::string& stdin,
+                 int timeout )
+{
+    return _target_env_command(
+        QStringList{ QString::fromStdString( command ) }, stdin, timeout ).first;
+}
+
 
 int
 target_env_call( const bp::list& args,
                  const std::string& stdin,
                  int timeout )
 {
-    return CalamaresUtils::System::instance()->
-           targetEnvCall( _bp_list_to_qstringlist( args ),
-                          QString(),
-                          QString::fromStdString( stdin ),
-                          timeout );
+    return _target_env_command(
+        _bp_list_to_qstringlist( args ), stdin, timeout ).first;
 }
 
 
@@ -114,7 +121,8 @@ check_target_env_call( const std::string& command,
                        const std::string& stdin,
                        int timeout )
 {
-    int ec = target_env_call( command, stdin, timeout );
+    auto ec = _target_env_command(
+        QStringList{ QString::fromStdString( command ) }, stdin, timeout );
     return _handle_check_target_env_call_error( ec, QString::fromStdString( command ) );
 }
 
@@ -124,9 +132,9 @@ check_target_env_call( const bp::list& args,
                        const std::string& stdin,
                        int timeout )
 {
-    int ec = target_env_call( args, stdin, timeout );
-    if ( !ec )
-        return ec;
+    auto ec = _target_env_command( _bp_list_to_qstringlist( args ), stdin, timeout );
+    if ( !ec.first )
+        return ec.first;
 
     QStringList failedCmdList = _bp_list_to_qstringlist( args );
     return _handle_check_target_env_call_error( ec, failedCmdList.join( ' ' ) );
@@ -138,15 +146,10 @@ check_target_env_output( const std::string& command,
                          const std::string& stdin,
                          int timeout )
 {
-    QString output;
-    int ec = CalamaresUtils::System::instance()->
-             targetEnvOutput( QString::fromStdString( command ),
-                              output,
-                              QString(),
-                              QString::fromStdString( stdin ),
-                              timeout );
+    auto ec = _target_env_command(
+        QStringList{ QString::fromStdString( command ) }, stdin, timeout );
     _handle_check_target_env_call_error( ec, QString::fromStdString( command ) );
-    return output.toStdString();
+    return ec.second.toStdString();
 }
 
 
@@ -155,16 +158,11 @@ check_target_env_output( const bp::list& args,
                          const std::string& stdin,
                          int timeout )
 {
-    QString output;
     QStringList list = _bp_list_to_qstringlist( args );
-    int ec = CalamaresUtils::System::instance()->
-             targetEnvOutput( list,
-                              output,
-                              QString(),
-                              QString::fromStdString( stdin ),
-                              timeout );
+    auto ec = _target_env_command(
+        list, stdin, timeout );
     _handle_check_target_env_call_error( ec, list.join( ' ' ) );
-    return output.toStdString();
+    return ec.second.toStdString();
 }
 
 void