Explore safey of YamlWireOut#sb re-use

[nicktindall]

I ignored the warning that indicates potentially unsafe re-use but there's a lot of them

They're not necessarily unsafe, it just indicates where sb is use in an outer scope then again in an inner scope. It could be that the outer scope doesn't care that the buffer gets trashed. Or it could be an issue like we've seen.

There are probably lots of "problematic" re-use patterns that look like this:

void doSomething() {
    //...
   try (ScopedResource<StringBuilder> sbR = acquireStringBuilder()) {
      StringBuilder sb = sbR.get();
      readFieldName(sb);
      if (sb.contentEquals("something")) {
         doSomethingElse():
      }
   }
}

void doSomethingElse() {
   try (ScopedResource<StringBuilder> sbR = acquireStringBuilder()) {
      StringBuilder sb = sbR.get();
      //...
   }
}

Which is actually not problematic, it's a false-positive to say that the above represents unsafe re-use. The way to solve that is to tighten up the outer scope e.g.

void doSomething() {
   //...
   if (fieldNameIs("something")) {
      doSomethingElse():
   }
}

void doSomethingElse() {
   try (ScopedResource<StringBuilder> sbR = acquireStringBuilder()) {
      StringBuilder sb = sbR.get();
      //...
   }
}

boolean fieldNameIs(String fieldName) {
   try (ScopedResource<StringBuilder> sbR = acquireStringBuilder()) {
      StringBuilder sb = sbR.get();
      readFieldName(sb);
      return sb.contentEquals(fieldName);
   }
}

[nicktindall]

Get rid of this ignore to see where we might have an issue

[nicktindall]

Note that this probably doesn't need to be a thread-local given that YamlWireOut is single-threaded anyway. Making a single-threaded implementation of ScopedResourcePool is trivial.

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
88.7% Coverage on New Code
5.4% Duplication on New Code

See analysis details on SonarCloud