ID 434540 - Custom soft effects do not inherit certain metadata values, unless it is specifically named "BurnIn"

Problem summary
Custom soft effect do not inherit certain metadata values, unless it is specifically named "BurnIn".

The "hiero/project", "hiero/sequence" and "hiero/sequence/timecode" appear to be the values which are not inherited.

Customer reported version
N/A

Customer reported platform
N/A

Steps to reproduce

1) Download the attached .gizmo file and save it to ~/.nuke directory

The gizmo contains the following nodes - it is the same as the standard BurnIn, just with an extra Text node (which doesn't call any metadata) just so you can easily tell the difference between it and the standard BurnIn: 

# custom_soft_effect.py - Example of registering a custom Soft Effect from hiero.ui import registerActionfrom PySide2.QtGui import QIconfrom PySide2.QtWidgets import QAction# This creates an action with an icon and effect named 'Awesome OCIO'action = QAction(QIcon("icons:LUT.png"), "Custom BurnIn", None)# Soft effect actions can be found by prefixing the QAction's objectName with: 'foundry.timeline.effect'action.setObjectName("foundry.timeline.effect.Custom_BurnIn")# You can optionally set a tooltip for this actionaction.setToolTip("This BurnIn won't display all metadata values")# Setting of Data here will point to the Nuke node class name.# Here, we assume there is a plugin with a Class name 'AwesomeOCIO'# Note: for soft effects to work, the Nuke node must use a gpuEngine implementation.action.setData("Custom_BurnIn")# This registers your custom action with the Effects MenuregisterAction(action)

3) Open Nuke Studio.

4) Import some footage (File > Import File(s)...) and drag the clip on to the Timeline.

5) Right click > Effects > Custom BurnIn. Notice that not all of the metadata is displayed in the Viewer.

If you repeat the above steps but name the Gizmo "BurnIn" (which will override the standard Nuke Studio BurnIn soft effect), all of the metadata will be displayed.

Expected behaviour
All of the metadata should be displayed.

Actual behaviour
The "hiero/project", "hiero/sequence" and "hiero/sequence/timecode" metadata values are not displayed. 

Workaround
Set the following environment variable:
FN_TIMELINE_DISABLE_METADATA_PRUNING=1

Using this environment variable should not make any difference, unless you are trying to share timeline disk cached frames between sequences and/or projects, or you do not want the disk cache to be invalidated if you change the sequence's frame rate or timecode.

Reproduced by support
This bug has been reproduced in:
Nuke Studio 12.1v2 - Windows 10 - Linux CentOS 7 - macOS 10.14 (Mojave)
Nuke Studio 12.0v1 - Windows 10
Nuke Studio 11.0v1 - Windows 10 - Linux CentOS 7 - macOS 10.14 (Mojave) - Regression

Unable to reproduce bug in:
Nuke Studio 10.5v8 - Windows 10 - Linux CentOS 7 - macOS 10.14 (Mojave)

Earliest version tested
Nuke Studio 10.5v8
- This issue doesn't appear in this version and has regressed