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

[Václav H. <wi...@us...>]

- **labels**:  --> properties
- Description has changed:

Diff:

~~~~

--- old
+++ new
@@ -1,31 +1,38 @@
-Unfortunately fShadowEnvironment doesn't go nice together with fAllowEmptyVars.
+Unfortunately `fShadowEnvironment` doesn't go nice together with `fAllowEmptyVars`.
 Here is the case. My config file contains the line:
+
+```properties
 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
-${ProgramData} is an environment variable I don't touch in the code
+
+- `${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).
+1. use `fShadowEnvironment`
 
-c) fShadowEnvironment | fAllowEmptyVars
-Which also doesn't work. As it will never read system variables.
+    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`
 
-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.
+2. `fAllowEmptyVars`
+    It will try to read every thing from System (will skip all custom variables).
 
+3. `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 found neither in properties nor in system variables.
+
+```cpp
             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 ()))
@@ -48,4 +55,4 @@
                // Nothing has been subtituted, just move beyond the
                 // unexpanded variable.
                 i = var_end + DELIM_STOP_LEN;
-~~~
+```

~~~~

- **assigned_to**: Václav Haisman



---

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

**Status:** open
**Group:** v1.1.3
**Labels:** properties 
**Created:** Tue Jun 20, 2017 06:57 PM UTC by Jan Vogelgesang
**Last Updated:** Wed Jun 21, 2017 10:22 AM UTC
**Owner:** Václav Haisman


Unfortunately `fShadowEnvironment` doesn't go nice together with `fAllowEmptyVars`.
Here is the case. My config file contains the line:

```properties
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:

1. 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`

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

3. `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 found neither in properties nor in system variables.

```cpp
            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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