Managed package cannot see a class from another managed package

Question

We have a following setup:

• a managed package pkg_a which provides a global virtual class Cls_A to be extended

• a managed package pkg_b which contains a global class Cls_B that extends pkg_a.Cls_A

• a static method in pkg_a's class which tries to retrieve a Type given its full name:

  public static Type findType(String fullName) {
      if (String.isBlank(fullName)) {
          return null;
      }
  
      Type foundType = Type.forName(fullName);
      if (foundType == null) {
          // now try to find it locally without package prefix
          foundType = Type.forName('', fullName);
  
          // try with package prefix
          if (foundType == null && fullName.contains('.')) {
              List<String> splitStr = fullName.split('\\.', 2);
  
              String namespace = splitStr[0];
              String className = splitStr[1];
  
              foundType = Type.forName(namespace, className);
          }
      }
      return foundType;
  }
  

When this method is called within pkg_a context:

    Type t = MyClass.findType('pkg_b.Cls_B');

it returns null for some reason. Does anyone know what are the possible reasons for this? Why wouldn't one managed package see a global class from another managed package, especially if this other class is extending package's own class?

What was checked so far:

• pkg_b.Cls_B is set to depend on the latest version of pkg_a

• Cls_B methods are public

• user running the pkg_a process which calls the findType() method has a System Adminstrator profile with access to all classes and packages, so it's unlikely that it's a permissions problem

• the most puzzling bit: this behaviour was noticed on an Enterprise edition org; on dev orgs everything works correctly

Answer 1

Well, other colleagues have run into the same issue, and found the underlying reason.

After pkg_a was installed, each package that was installed after it added a version dependency to pkg_a's classes, e.g. after pkg_b v1.23 was installed, pkg_a's classes had pkg_b v1.23 dependency added to them. After the packages were updated, however, all classes in pkg_a that weren't modified/updated didn't have their dependencies updated either. So, after pkg_b was updated to v1.25, unmodified classes from pkg_a still had a dependency on pkg_b v1.23. Cls_B was introduced in v1.25, so an unmodified class from pkg_a couldn't see it since it still had a dependency on v1.23. Changing the dependency version manually while logged on as a Subscriber didn't work, SFDC returned an error "Only code in local namespace can be changed" (or a similar message in the same vein).

The problem was solved by modifying the class in pkg_a that tries to reference classes from other packages - an empty line or two were added - and creating a patch release which was installed on the target org. This caused SFDC to see the affected class as modified, recompiling it and updating the package dependencies on it.