ppkarwasz commented on issue #2679:
URL:
https://github.com/apache/logging-log4j2/issues/2679#issuecomment-2210407353
To be more precise, the `StrLookup` parses the string
`${env:TZ:-%d{yyyy-MM-dd HH:mm:ss}{GMT+00}}` as:
1. A lookup expression (`${env:TZ:-%d{yyyy-MM-dd HH:mm:ss}`), where `env:TZ`
is the key used for the lookup and `%d{yyyy-MM-dd HH:mm:ss}` is the default
value.
2. The literal `{GMT+00}}`.
The main problem here is to have a **coherent** set of escape rules for
lookup expressions and pattern expressions.
Right now we have the following escaping rules:
* the special sequence `${` can be escaped as `$${`. This only works for the
first level of lookups. If `${foo}` expands to `bar`, then `$${foo}` is not
expanded, but `${$${foo}}` returns the expansion of `${$bar}`.
* the special sequence `:-` can be escaped as `:\-`, but if `\-` appears
anywhere else, it will give two characters.
* the pattern sequence `%d` can be escaped as `%%d`.
* there is **no** way to escape a closing brace `}` neither in a lookup nor
in the options of a pattern expression.
This resembles more the way [`cmd.exe` parses a command
line](https://stackoverflow.com/a/4095133/11748454) than the simpler `bash`
expansion.
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