library/cpp/testing/common/scope.h


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#pragma once 
 
#include <util/generic/string.h> 
#include <util/generic/vector.h> 
#include <util/system/env.h> 
 
#include <utility> 
 
namespace NTesting { 
    // @brief Assigns new values to the given environment variables and restores old values upon destruction. 
    // @note if there was no env variable with given name, it will be set to empty string upon destruction IGNIETFERRO-1486 
    struct TScopedEnvironment { 
        TScopedEnvironment(const TString& name, const TString& value) 
            : PreviousState{1, {name, ::GetEnv(name)}} 
        { 
            ::SetEnv(name, value); 
        } 
 
        TScopedEnvironment(const TVector<std::pair<TString, TString>>& vars) 
            : PreviousState(Reserve(vars.size())) 
        { 
            for (const auto& [k, v] : vars) { 
                PreviousState.emplace_back(k, ::GetEnv(k)); 
                ::SetEnv(k, v); 
            } 
        } 
 
        ~TScopedEnvironment() { 
            for (const auto& [k, v] : PreviousState) { 
                ::SetEnv(k, v); 
            } 
        } 
 
        TScopedEnvironment(const TScopedEnvironment&) = delete; 
        TScopedEnvironment& operator=(const TScopedEnvironment&) = delete; 
    private: 
        TVector<std::pair<TString, TString>> PreviousState; 
    }; 
}