[Log4cplus-devel] [log4cplus:bugs] #342 fShadowEnvironment does not allow for optional variables (which can be empty)

[Jan V. <jan...@us...>]

I think the code should be changed to something like:
            
            bool propertyExist = props.exists(key);
			if (propertyExist)
			{
				replacement = props.getProperty(key);
			}

			// if shadowing is not allowed or a property was not registered then try to look up in envrionment variables
			if (!shadow_env || !propertyExist)  
			{
				internal::get_env_var(replacement, key); 
			}
			
			// if empty values allowed or value is not empty then perform remplacement 
            if (empty_vars || !replacement.empty ())
            {
                ....
              


---

** [bugs:#342] fShadowEnvironment does not allow for optional variables (which can be empty)**

**Status:** open
**Group:** v1.1.3
**Created:** Tue Jun 20, 2017 06:57 PM UTC by Jan Vogelgesang
**Last Updated:** Tue Jun 20, 2017 07:06 PM UTC
**Owner:** nobody


Unfortunately fShadowEnvironment doesn't go nice together with fAllowEmptyVars.
Here is the case. My config file contains the line:
appender.applog.File=${ProgramData}\${logname}-${USERNAME}${optionalSuffix}.log
So I have both Environment Variables and my custom variables which I set in the code.
${OptionalSuffix} is added only if app is run from command line, otherwise I would like to have it empy. 
${UserName} I set manually in the code only when app is run as a services.
${logname} is my log name set in the code
${ProgramData} is an environment variable I don't touch in the code
I have 3 options:
a) use fShadowEnvironment
Then I will have correctly resolved all variables but when ${optionalSuffix} is empty then I will end up with the log name:
C:\ProgramData\MyLogName-janekvogel${optionalSuffix}.log

b) fAllowEmptyVars:
It will try to read every thing from System (will skip all custom variables).

c) fShadowEnvironment | fAllowEmptyVars
Which also doesn't work. As it will never read system variables.

I think the best approach would be just to remove the not resolved property. So in fShadowEnvironment ${optionalSuffix} should be replaced with empty string if optionalSuffix is not found neither in properties nor in system variables.

            else
               // Nothing has been subtituted, just move beyond the
                // unexpanded variable.
               // TODO: replace unresolved property with empty string
               i = var_end + DELIM_STOP_LEN;

~~~
       if (shadow_env)
                replacement = props.getProperty (key);
            if (! shadow_env || (! empty_vars && replacement.empty ()))
                internal::get_env_var (replacement, key);
            
            if (empty_vars || ! replacement.empty ())
            {
                // Substitute the variable with its value in place.
                pattern.replace (var_start, var_end - var_start + DELIM_STOP_LEN,
                    replacement);
                changed = true;
                if (rec_exp)
                    // Retry expansion on the same spot.
                    continue;
                else
                    // Move beyond the just substituted part.
                    i = var_start + replacement.size ();
            }
            else
               // Nothing has been subtituted, just move beyond the
                // unexpanded variable.
                i = var_end + DELIM_STOP_LEN;
~~~


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