Include variables generated in first play of playbook - automation

Question

I have a playbook which consists of two plays:
1: Create inventory file and variables file on localhost
2: Use the variables in commands on generated inventory
Example playbook:
---
- name: Generating inventory and variables
hosts: localhost
vars_files:
- variables.yml #variables file used for automating
tasks:
- name: Creating inventory template
template:
src: hosts.j2
dest: "./inventories/{{location}}/hosts"
mode: 0777
force: yes
ignore_errors: yes
run_once: true
- meta: refresh_inventory
- name: Creating predefined variables from a template
template:
src: predefined-vars.yml.j2
dest: "./variables/predefined-vars.yml"
- name: Setting vlan to network devices
remote_user: Ansible
hosts: all
vars_files:
- variables.yml #variables file used for automating.
- variables/predefined-vars.yml
tasks:
- name: configure Junos ROUTER for vlan
include_tasks: ./roles/juniper/tasks/add_vlan_rt.yml
when:
- inventory_hostname in groups['junos_routers']
- groups['junos_routers'] | length == 1
- location == inventory_name
This gives undefined variable error (for a variable created in the first play).
Is there a way to do this? I use this for generating variables like router_port_name and so on - the variables depend on location and dedicated server, which are defined in variables.yml
Any help is really appreciated.
Thanks
EDIT: However, I have noticed that this playbook:
---
- hosts: localhost
gather_facts: false
name: 1
vars_files:
- variables.yml
tasks:
- name: Creating predefined variables from a template
template:
src: predefined-vars.yml.j2
dest: "./variables/predefined-vars.yml"
- name: Generate hosts file
hosts: all
vars_files:
- variables.yml
- ./variables/predefined-vars.yml
tasks:
- name: test
debug: msg="{{ router_interface_name }}"
show the variables created in the first play.
The difference I see is that the first playbook reads all variable files (even predefined-vars.yml <- created at first play, used at the other) used in the playbook at the start of the first play (generating inventory and creating variable file) while the second playbook reads variables.yml in first play and only at the start of the second play reads the predefined-vars.yml .
Any Ideas how to make the first playbook behave the same way?

Answer 1

So I have found the solution to the problem, based on the documentation and suggestions from other people.
What I understood about the problem:
A playbook will read all the variables (of all plays) provided into the cache for later use, so if I include my predefined-vars.yml into vars_files, then after changing it in first play, the changes will not be used by later plays because they will use cache for that.
Thus I had to create another task in second play, which would read (load into cache) my newly generated file (for that play):
- name: Include predefined vars
include_vars: ./variables/predefined-vars.yml
run_once: true
Hope this helps you!
Still have no idea why second play shows the variables...