composer update keeps overwriting parameters.yml when using custom values

I have some custom entries in my parameters.yml, every time I run a composer update, it wants to add the missing entries, which even worse overwrites my custom entries. How can I stop this?

e.g. before composer update

#parameters.yml
# Env = GLOBAL
parameters:
# DB settings - GLOBAL
database_driver: pdo_mysql
database_host: 127.0.0.1
database_port: 3306

#mailer settings
mailer_to: yo@yo.com
mailer_from: yo@site.com
mailer_transport: smtp
mailer_subject: ":-| Something is broken!"

# Framework use - GLOBAL
locale: en

after

#parameters.yml
# This file is auto-generated during the composer install
parameters:
database_driver: pdo_mysql
database_host: 127.0.0.1
database_port: 3306
mailer_transport: smtp
locale: en
database_name: 
database_user: 
database_password: 
mailer_host: 
mailer_user: 
mailer_password: 
secret:

Luckily my repo and my working file through my ide are two different files and need to be synced. after i run composer update, when i run a sync, i download all files to my IDE except for the parameters.yml, that one i push back up to overwrite the one that was just auto created.

I would like to eliminate this hassle, as I keep my db passwords on a per/env file.

EDIT: When I try to fill in the unneeded vars as dummy values by nulling them out, it backfires as well.

$ composer update
Loading composer repositories with package information
Updating dependencies (including require-dev)
Generating autoload files
Updating the "app/config/parameters.yml" file
Some parameters are missing. Please provide them.
database_name: null
database_user: null
database_password: null
mailer_host: null
mailer_user: null
mailer_password: null
secret: null

  [Symfony\Component\DependencyInjection\Exception\ParameterNotFoundException]
  You have requested a non-existent parameter "mailer_from".

Script Sensio\Bundle\DistributionBundle\Composer\ScriptHandler::clearCache handling the post-update-cmd event terminated with an exception

  [RuntimeException]
  An error occurred when executing the "'cache:clear --no-warmup'" command.

The custom param is causing problems itself as well.

So now I go to peek at my newly generated file, and it looks like this

# This file is auto-generated during the composer install
parameters:
    database_driver: pdo_mysql
    database_host: 127.0.0.1
    database_port: 3306
    mailer_transport: smtp
    locale: en
    database_name: null
    database_user: null
    database_password: null
    mailer_host: null
    mailer_user: null
    mailer_password: null
    secret: null

But what i need it to say after regenerating ideally is this

/**
* my custom comment and copyright/legal tamper warning
*/
#  Env = GLOBAL
parameters:
  # DB settings - GLOBAL
  database_driver: pdo_mysql
  database_host: 127.0.0.1
  database_port: 3306

  #mailer settings
  mail_to: me@site.com
  mail_from: site@site.com
  mail_transport: smtp
  mail_subject: ":-| Something is broken!"

  # Framework use - GLOBAL
  locale: en

The rest of my parameters are located on another parameters file, that is dynamically included depending on what env loads, and has different db creds on them each.

EDIT per @AlpineCoder answer: my latests findings why adding dummy values doesnt work

When I add this to my parameters.yml

#dummy values  to avoid regeneration
    database_name: dummyvalue
    database_user: dummyvalue
    database_password: dummyvalue
    mailer_host: dummyvalue
    mailer_user: dummyvalue
    mailer_password: dummyvalue
    secret: dummyvalue

It no longer asks me to fill in these values, thats great, however, it still regenerates the file, deleting all my custom values, leaving me with this

# This file is auto-generated during the composer install
parameters:
    database_driver: pdo_mysql
    database_host: 127.0.0.1
    database_port: 3306
    mailer_transport: smtp
    locale: en
    database_name: dummyvalue
    database_user: dummyvalue
    database_password: dummyvalue
    mailer_host: dummyvalue
    mailer_user: dummyvalue
    mailer_password: dummyvalue
    secret: dummyvalue

Solution

You have two options, either fill out your parameters.yml.dist or you can go to your composer.json file and in the post-update-cmd and post-install-cmd you should see something like:

"Incenteev\\ParameterHandler\\ScriptHandler::buildParameters",

if you remove that line, your parameters will no longer be changed when you run composer.

If you're collaborating with other people, updating your parameters.yml.dist will probably be the better way to go though as it will help remind them they need to fill out new parameters when new ones are introduced.