ZDoom

class HG_DoorBlocker : SwitchableDecoration
{
	HG_DoorBase door;
	bool doorWasBlocked;

	Default
	{
			radius 40;
			height 80;
	
			RenderStyle "None";
	
			+SOLID
			+NOGRAVITY
			
			
			Activation THINGSPEC_MonsterTrigger | THINGSPEC_Switch;
			+BUMPSPECIAL
			//+USESPECIAL
	}
	
	override bool cancollidewith (actor other, bool passive)
	{
		if(passive == true && other != null)
		{
			if(other.health > 0 && other.bSOLID == true && (PlayerPawn(other) != null || other.bISMONSTER == true))
			{
				if(door != null)
				{
					door.blocked = true;
					if(door.isOpen == false || door.closing == true)
					{
						door.Activate(other);
					}
				}
				
			}
		}
		
		return false;
	}
	
	int doorBlockTimer;
	
	override void Tick()
	{
		Super.Tick();
		if(door != null)
		{
			if(door.blocked == true)
			{
				if(doorBlockTimer < 4)
				{
					doorBlockTimer++;
					if(doorBlockTimer >= 4)
					{
						door.blocked = false;
						doorBlockTimer = 0;
					}
				}
				
			}
		}
	}
	
	/*
	override void Tick()
	{
		Super.Tick();
		if(master)
		{
			HG_DoorBase door = HG_DoorBase(master);
			if(door.isOpen == true)
			{
				//RadiusGive?
				if(CheckProximity("PlayerPawn", 45.0, 1, CPXF_ANCESTOR))
				{
					door.blocked = true;
					//A_Log("blocked");
				}
				else {
					door.blocked = false;
					//A_Log("not blocked");
				}
			}
		}
	}
	*/
	
	override void Activate(Actor activator)
	{
		if(activator != null)
		{
			if(abs(activator.pos.z - self.pos.z) > 80)
			{
				return;
			}
		}
		if(master)
		{
			master.Activate(activator);
		}
	}
	
	override void Deactivate(Actor activator)
	{
		Activate(activator);
	}

	States
	{
		Spawn:	
		FRAM A 1;
		Loop;
	}
}

It's certainly possible, I created a door like this for my Hired Guns TC. The door consists of the door itself, which is an actor, and a "blocker", which is the door's child and handles activation. So, when a player of monster collides with the blocker, the blocker will either reset the door's closing timer if it's open, or start the opening process (or reverse the closing process). There may be problems with hitscan attacks, I can't remember to be honest.

Here is the door blocker code.

[code]class HG_DoorBlocker : SwitchableDecoration
{
HG_DoorBase door;
bool doorWasBlocked;

Default
{
radius 40;
height 80;

RenderStyle "None";

+SOLID
+NOGRAVITY


Activation THINGSPEC_MonsterTrigger | THINGSPEC_Switch;
+BUMPSPECIAL
//+USESPECIAL
}

override bool cancollidewith (actor other, bool passive)
{
if(passive == true && other != null)
{
if(other.health > 0 && other.bSOLID == true && (PlayerPawn(other) != null || other.bISMONSTER == true))
{
if(door != null)
{
door.blocked = true;
if(door.isOpen == false || door.closing == true)
{
door.Activate(other);
}
}

}
}

return false;
}

int doorBlockTimer;

override void Tick()
{
Super.Tick();
if(door != null)
{
if(door.blocked == true)
{
if(doorBlockTimer < 4)
{
doorBlockTimer++;
if(doorBlockTimer >= 4)
{
door.blocked = false;
doorBlockTimer = 0;
}
}

}
}
}

/*
override void Tick()
{
Super.Tick();
if(master)
{
HG_DoorBase door = HG_DoorBase(master);
if(door.isOpen == true)
{
//RadiusGive?
if(CheckProximity("PlayerPawn", 45.0, 1, CPXF_ANCESTOR))
{
door.blocked = true;
//A_Log("blocked");
}
else {
door.blocked = false;
//A_Log("not blocked");
}
}
}
}
*/

override void Activate(Actor activator)
{
if(activator != null)
{
if(abs(activator.pos.z - self.pos.z) > 80)
{
return;
}
}
if(master)
{
master.Activate(activator);
}
}

override void Deactivate(Actor activator)
{
Activate(activator);
}

States
{
Spawn:
FRAM A 1;
Loop;
}
}[/code]

I'm attempting to do something with CheckProcimity to see if the player is nearby I thought I used it wrong until I found this thread. The example provided by TheSeventh works flawlessly when I run his example.wad but if I rebuild his level or use his script in my level it always returns false for the proximity check. Running latest nightly GZDoom build.

#include "zcommon.acs"

Script "AutomaticDoor" Enter
{
	if (CheckProximity(2,"DoomPlayer",256.0, 1) )//The 2 here is the mapspot
		{
		Door_Open(1, 60);//Open the door
		}
	else
	 	{
	 	Door_Close(1, 60);//And close it when the player isn't there.
	 	}
	delay(35);
	restart;
}

I just threw this together with an edit to the CheckProximity example from the wiki. I'm sure you could use A_LookEx and state jumps which trigger ACS_NamedExecute but I figured since you would have to resort to ACS anyway to alter the map I thought it was better to start there instead.

Tag 1 is the door sector and Tag 2 is the MapSpot which I placed in the doorframe but you could easily place it anywhere else and it should function appropriately.
[code]
#include "zcommon.acs"

Script "AutomaticDoor" Enter
{
if (CheckProximity(2,"DoomPlayer",256.0, 1) )//The 2 here is the mapspot
{
Door_Open(1, 60);//Open the door
}
else
{
Door_Close(1, 60);//And close it when the player isn't there.
}
delay(35);
restart;
}
[/code]

I'm not sure if it's good practice to reference "DoomPlayer" here or if it would be better to look for "PlayerPawn" or something like that but for vanilla doom this works and you could probably use a modded playerpawn name instead if you were using one.

The .zip is an example map I threw together to demonstrate the script.

Yes, good thinking. How to realize this actor?

I wonder if some sort of "motion sensor" actor could be possible? i.e. an invisible actor placed near the door that looks for the player; if the player is within a certain distance of the actor, it opens the door (via ACS or ZScript (if that can be done)), if the player moves out of that distance, the door can close.

Hey! How to realize smart door opening/closing like in Doom 3? When player in range of door it must open and check player's presence in door's range. Door must close only after player is out of range and open again if player in door's range while it closing. I was trying using simple open/close lines, but thing is player can out of door's range while door is opening/closing.
old example:
https://imgur.com/a/bhWERd8
p.s.: sorry for terrible English