IPM Update Resource Conflict

[isc-jlechtne]

Describe the bug

This is similar in concept to the issue #1119 except with resources instead of dependency versions. This comes up in a case where a resource is moved from one module to another.

ERROR! Resource 'MyClass.CLS' is explicitly part of module 'module-b', and cannot also be in module 'module-c'

To Reproduce

Using the same module setup as in #1119, but adding a resource MyClass.CLS to the scenario:

1. Have modules A, B, & C. Module A depends on B which in turn depends on C
2. Pre update setup:

• Module A (2.0.0)
• Module B, has resource MyClass.CLS
• Module C

3. Post update versions

• Module A (2.1.0+snapshot)
• Module B
• Module C, has resource MyClass.CLS

4. Run zpm "install <Module A> 2.0.0"
5. Run zpm "update <Module A> 2.1.0+snapshot" (this should error)

Expected behavior

Expected behavior is for Module A and all of its dependencies to successfully update as MyClass.CLS is only a part of module-c in the post-update environment (no longer with module-b).

[isc-jlechtne]

Did some investigation on ordering of modules with update as some succeed while others fail. Takeaway was that this error is only present in cases where the module the resource is moved to has it's update module.xml loaded prior to the module where the resource is pre-update. This makes sense as that's where there would be a moment in the process where the resource exists in the respective version of both modules.

The ordering of loading the module documents goes as: 1) base module the update is called on followed by 2) dependencies in reverse order of depth (furthest transient to direct dependencies). For the setup in this issue's description this goes A > C > B. So, if instead MyClass.CLS moved from C to B, we wouldn't encounter this issue. We instead would have a moment where MyClass.CLS is not associated with any module in the environment.