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Please describe how to make add-on development more efficent (e.g. reloading)
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Description

Problem

No clear documentation on how to setup an efficient development environment and reload an add-on during development, leading to slow and frustrating experiences by newer add-on developers.

Explanation

Imagine being a new add-on developer who just finished the Add-on Tutorial (https://docs.blender.org/manual/en/dev/advanced/scripting/addon_tutorial.html#intended-audience). You wrote a .py file and wonder, do I really need to add every .py file through Preferences ‣ Add-ons ‣ Install…?

  • Please mention that you can set a default script location with: Edit ‣ Preferences ‣ File Paths ‣ Data ‣ Scripts.

Next, we realize you rather write "create blocks" as "Create Blockies", but wait, or add-on is already loaded. How do I reload the add-on? Do I really have to close Blender every time? With your Google skills (https://blender.stackexchange.com/questions/2691/is-there-a-way-to-restart-a-modified-addon) you find that F8 should reload all add-ons... except it doesn't, because that's for 2.79. Luckily you read through the comments and realize you have to go through the painful process of searching for F3 -> reload scripts -> enter every time we need to reload a change. In the other answer you find bpy.ops.wm.addon_enable(module='your_module_name') for in the Blender terminal, which might be slightly faster (just arrow-up -> enter). You continue for a while and started to make a multi-file add-on. Suddenly your code shortcut doesn't reload every change you make? After some experimenting you find out that only changes in __init__.py are noticed, so you go to (https://blender.chat/channel/python) and ask what is wrong (https://blender.chat/channel/python?msg=fGEyJtjNZqfpApxQ5). Which doesn't solve your issue, so you dive in the code of `bpy.ops.wm.addon_enable() and make an issue about it (https://developer.blender.org/T66924). There, someone points out that actually bpy.ops.script.reload() is the right code command, not bpy.ops.wm.addon_enable(module='your_module_name')

  • Please mention that you can reload ALL add-ons with F3 -> reload scripts -> enter or the correct code line bpy.ops.script.reload().

You hear you can set a keyboard shortcut for reload, so you find an image about it (https://devtalk.blender.org/t/reload-button-in-2-8/1708). The image there doesn't tell you how to set the keyboard shortcut and Preferences -> Keymap -> Search -> "reload script" doesn't show up anything. So you Google now: "Blender 2.8 how to add a new shortcut", which shows only "Blender 2.8 changed these shortcuts!", so you add "your own", only to find this page saying it has not been implemented yet (https://blender.stackexchange.com/questions/124475/blender-2-8-how-to-add-a-new-shortcut). Then in a 2.79 YouTube video you find you first have to collapse a line (e.g. Screen -> Global where a button Add New shows up.

  • Please include in the docs how to set a keyboard shortcut for add-on reloading: Preferences -> Keymap -> Screen -> Screen (Global) -> Add New -> collapse -> see image.

  • Please also include (a link to) how to setup an IDE to develop your add-ons with.

Add-on reloading

Please also include that the beginning of your file needs a structure like this if you want to reload add-ons:

# Check if this add-on is being reloaded
if "bpy" in locals():
    # reloading .py files
    import importlib
    # from . blendzmq_props import ZMQSocketProperties
    # importlib.reload(ZMQSocketProperties)
    # from . blendzmq_panel import BLENDZMQ_PT_zmqConnector
    # importlib.reload(BLENDZMQ_PT_zmqConnector)

    from . import addon_props  # addon_props.py (properties are created here)
    importlib.reload(addon_props)  # does this file need a def register() / def unregister() for the classes inside?
    from . import addon_panel  # addon_panel.py (panel interface classes are created here)
    importlib.reload(addon_panel)
# or if this is the first load of this add-on
else:
    print("importing .py files")
    import bpy
    from . import addon_props
    from . import addon_panel

Request

By reading this, you might have noticed that getting into efficient Blender add-on development is quite frustrating with the current documentation. Please make an extra page about how to setup you add-on development environment, using the bullet points above, here: https://docs.blender.org/manual/en/dev/advanced/scripting/addon_tutorial.html#intended-audience

Event Timeline

Iemand Iets (NumesSanguis) renamed this task from Please describe how to make add-on development more efficent to Please describe how to make add-on development more efficent (e.g. reloading).Jul 21 2019, 4:35 PM

Just a quick note, addon reloading can also be done differently. This Visual Studio code extension does the reloading automatically: https://marketplace.visualstudio.com/items?itemName=JacquesLucke.blender-development

Personally, I'm not really a big fan of the reloading code you mention, but yeah, it is used in many addons...

Aaron Carlisle (Blendify) lowered the priority of this task from 90 to Normal.Dec 21 2019, 2:40 AM

The reload code is incorrect. The return value of importlib.reload() should be assigned to the local name of the reloaded module, or addon_props and addon_panel will still refer to the old module.

This style of addon reloading code fixes that, and as an added benefit it is also compatible with MyPy type checking:

import bpy

# Check if this add-on is being reloaded
if "addon_props" not in locals():
    from . import addon_props, addon_panel
else:
    import importlib

    addon_props = importlib.reload(addon_props)
    addon_panel = importlib.reload(addon_panel)

By not checking the name "bpy" but one of the addon's imported modules, it's also possible to just import bpy like any other module, and have the PEP 8 suggested order of "standard library", "third party", "own code" in the imports.

The MyPy compatibility comes from having the import first, and the reload later. This makes it possible to parse the file top-to-bottom. I suspect that some IDEs may also prefer this order.

This comment was removed by -- (zgorg).

I have the same gripes. To make matters worse, running bpy.ops.script.reload() causes blender to crash for me. I'll keep looking for that better workflow as well. Hang in there!