API command for general Edit Mode toggling (TAB press)?

Question

I tried imitating Blender's TAB press (Edit Mode Toggle) by using object.mode_set(mode='EDIT'), but this doesn't work for grease pencil objects which require object.mode_set(mode='EDIT_GPENCIL') instead.

I checked the keymap editor but the Enum property there doesn't even match the documentation:

Am I being silly or what is going on here?

TLDR

What API command can I use to match the default behavior of TAB press (not have to worry about object types like mesh vs grease_pencil)?

EDIT: Thanks batfinger and Marcus for helping out!

Answer 1

Keymap sets a toggle.

The operator has two properties, mode and toggle

>>> bpy.ops.object.mode_set(
mode_set()
bpy.ops.object.mode_set(mode='OBJECT', toggle=False)
Sets the object interaction mode

Mesh object active

The TAB Shortcut The toggle property is set to True.

which correlates to

bpy.ops.object.mode_set(mode='EDIT', toggle=True)

GPencil object active

Why is it blank when GP is active, the keymap uses 'EDIT' as the setting, which is not available as an enum item. (See below) Appears to be some dodgy fix in place behind the scenes, replacing 'EDIT' with a startswith 'EDIT' option.

The shortcut can be emulated by emulating this.

import bpy
ob = bpy.context.object

bpy.ops.object.mode_set(
        mode = 'EDIT_GPENCIL' if ob.type == 'GPENCIL' else 'EDIT',
        toggle=True,
        )

use this in your scripts to emulate tab.

Dynamic Enum

On the "Non Matching". An enum property can be dynamic, ie items added / removed based on context. If a grease pencil object is active the options are different for if a mesh object is active, etc.

The documentation shows all possible items, of which only a subset will be valid, based on context.

EDIT

On further investigation, the shortcut is using

bpy.ops.gpencil.editmode_toggle()

this can be confirmed by pressing TAB with GP object active and in python console

>>> C.active_operator
<bpy_struct, Operator("GPENCIL_OT_editmode_toggle") at 0x7f3221be1988>

>>> C.window_manager.operator_properties_last('gpencil.editmode_toggle').back
False

when the context object is a gpencil, so without any knowledge of context, could use a try catch clause

import bpy

try:
    bpy.ops.object.mode_set(
            mode = 'EDIT',
            toggle=True,
            )
except TypeError:
    bpy.ops.gpencil.editmode_toggle()

which will still throw a runtime error if the context object is None for example.