JWT007 opened a new issue, #3172:
URL: https://github.com/apache/logging-log4j2/issues/3172
DefaultMergeStragegy (Log4j 2.24.1)
I *think* I may have encountered a potential error if using a
CompositeConfiguration.
In the `DefaultMergeStrategy#mergeConfigurations`, it does a double loop
over the source and target node's children - merging from the source into the
target.
In these loops it provides special handling for PROPERTIES, SCRIPTS,
APPENDERS, FILTERS and LOGGERS.
If the element tag name does not match one of these, the default behaviour
is to add the children of the source element to the corresponding target
element.
```
switch (toRootLowerCase(targetChildNode.getName())) {
case PROPERTIES:
case SCRIPTS:
case APPENDERS: { ... }
case LOGGERS: { ... }
default: {
targetChildNode.getChildren().addAll(sourceChildNode.getChildren());
isMerged = true;
break;
}
}
```
If however, two configurations had an `AsyncWaitStrategyFactory` element:
```
<Configuration>
<AsyncWaitStrategyFactory class="a.b.c.Foo">
</Configuration>
<Configuration>
<AsyncWaitStrategyFactory class="d.e.f.Bar">
</Configuration>
```
This element has no children, and the attributes are not merged.
The 'class' attribute after merging would be taken from the first occurrence
`a.b.c.Foo` and not from the *override* 'd.e.f.Bar`.
I'll admit I have not tested this scenario, but reviewing the code it
*logically* seems like it might cause a problem
NOTE: "Properties", "Scripts", "Appenders", "Filter" and "Loggers" are all
collection elements and have no attributes - so it makes sense that for these
no attributes are merged, but the default behavior should IMHO handle the
possiblity of attributes and perform a merge of the element's attributes
similar to that of the `DefaultMergeStrategy#mergeRootProperties` method.
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