[MSHADE-156] shade plugin is transforming also strings that are not supposed to be transformed

**[Neeme Praks](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=neeme)** opened **[MSHADE-156](https://issues.apache.org/jira/browse/MSHADE-156?redirect=false)** and commented

I'm shading several third party libraries into a single JAR. In the context of this issue, there are two important libraries:

1. com.nothome:javaxdelta:2.0.1 - this library is in "at.spardat.xma.xdelta" package.
2. ch.qos.logback:logback-classic:1.0.11 - in this library, in class ch.qos.logback.classic.spi.StackTraceElementProxy, there is a method to convert stack trace elements into strings:

```
public String getSTEAsString() {
if (steAsString == null) {
steAsString = "at " + ste.toString();
}
return steAsString;
}
```

I use "org.myorgname.appname.shaded" package for shading.

During shading, the constant "at " is replaced with "org.myorgname.appname.shaded.at" -- shade plugin thinks that the "at" in the beginning of that string is a package name and shades it.

This results in an unfortunate side-effect: all logged stack traces now look like this:

```
Caused by: java.util.zip.ZipException: error in opening zip file
org.myorgname.appname.shaded.at java.util.zip.ZipFile.open(Native Method) ~[na:1.6.0_19]
org.myorgname.appname.shaded.at java.util.zip.ZipFile.(ZipFile.java:114) ~[na:1.6.0_19]
org.myorgname.appname.shaded.at java.util.zip.ZipFile.(ZipFile.java:131) ~[na:1.6.0_19]
```

Possible fixes:
* instead of just checking the first part of the package (at), check for the full package (at.spardat.xma.xdelta).
* allow to configure shade plugin to ignore certain string constants in certain classes (this would solve also some other issues we have with shade plugin being too eager).
* both of the above.

---

**Affects:** 2.1

**Issue Links:**
- [SLING-8092](https://issues.apache.org/jira/browse/SLING-8092) Relocation in Content Extension too bold
(_**"causes"**_)
- [FLINK-13044](https://issues.apache.org/jira/browse/FLINK-13044) Shading of AWS SDK in flink-s3-fs-hadoop results in ClassNotFoundExceptions
(_**"breaks"**_)

**Remote Links:**
- [GitHub Pull Request #249
](https://github.com/apache/maven-shade-plugin/pull/249)

9 votes, 15 watchers

Start by tracing the Maven Shade Plugin's handling of string constants during package relocation, using the reported StackTraceElementProxy.getSTEAsString example as the reproduction case. Compare the proposed full-package matching and configurable exclusions, then verify that ordinary stack-trace strings are unchanged while legitimate package references still relocate.

Written by the indexing model from the issue text.