2d spring implementation for godot v4 gdscript, simply assign a and b RigidBody2D, script doesn't have to be attached to rigidbodys, just needs to be in the scene

spring.gd

extends Node2D

@export
var a: RigidBody2D = null
@export
var b: RigidBody2D = null
@export
var a_affected: bool = false
@export
var b_affected: bool = false
@export
var stiffness = 10
@export
var rest_length = 10
@export
var damping = 0.5

#a.position - b.position
var v_pos_diff = Vector2()
#calculated length currently at
var v_actual_length: float = 1
#normalized direction from a to b
var v_a_dir = Vector2()
#v_a_dir as euler
var v_a_angle = Vector2()

var v_b_dir = Vector2()
var v_b_angle = Vector2()
#diff of body velocities
var v_vel_diff = 0
#dot product of a-b velocity and a->b direction
var v_vel_diff_dot = 0
#current damping applied in step
var v_damp_force = 0
#spring to resting length force
var v_spring_force = 0
var v_total_force = 0

var v_a_force = Vector2()
var v_b_force = Vector2()

# Called when the node enters the scene tree for the first time.
func _ready():
	pass # Replace with function body.

# Called every frame. 'delta' is the elapsed time since the previous frame.
func _physics_process(delta):
	if a == null or b == null:
		return
	
	#doesn't create a new vec, just fyi
	v_pos_diff = b.position - a.position
	
	v_actual_length = v_pos_diff.length()
	
	v_a_dir = v_pos_diff.normalized()
	v_a_angle = v_a_dir.angle()
	
	v_b_dir = -v_a_dir
	v_b_angle = v_b_dir.angle()
	
	v_vel_diff = b.linear_velocity - a.linear_velocity
	v_vel_diff_dot = v_vel_diff.dot(v_a_dir)
	
	#calculate damp force
	v_damp_force = v_vel_diff_dot * damping
	
	#Hooke's law spring force
	v_spring_force = (v_actual_length - rest_length) * stiffness
	v_total_force = v_spring_force + v_damp_force
	
	v_a_force = (v_a_dir * v_total_force) / a.mass
	v_b_force = (v_b_dir * v_total_force) / b.mass
	
	if not a_affected and not a.freeze:
		a.apply_central_force(v_a_force)
	if not b_affected and not b.freeze:
		b.apply_central_force(v_b_force)
	
	self.position = a.position.lerp(b.position, 0.5)
	self.rotation = v_a_angle
	self.scale.x = v_actual_length / rest_length
	
	pass

Revision 2: extends Node2D, scales self x based on a and b rigid bodies, positions self between a and b rigid bodies, rotates to align between a and b rigid bodies. You can attach a visual object as a child to the spring to represent the spring on screen and have full control of what is rendered.