Terraform - how to modify a existing S3 bucket that was created from module?

Question

I already have my S3 bucket called foo-name created and existing with terraform. I want to modify the existing s3 bucket and a policy. But when I do this it seems to want to add a new s3 bucket instead. I imagine s3_website in resource "aws_s3_bucket" "s3_bucket" is incorrect. But I don't know what I would use in place of that because of the way the S3 bucket was corrected.

How do I get it to modify my existing S3 bucket that was created in module s3_website {}?

provider "aws" {
  alias = "east1"
  region = "us-east-1"
}

module "acm_cert" {
  source = "foo-git"

  cluster = var.cluster

  domain      = var.website_domain
  dns_zone    = var.zone_name

  tags       = var.tags
  extra_tags = var.extra_tags

   providers = {
    aws = aws.east1
  }
}

module s3_website {
  source = "foo-git"

  cluster        = var.cluster
  env            = var.tags.Environment
  app            = var.tags.Application
  website_domain = var.website_domain
  s3_prefix      = var.s3_prefix

  certificate_arn = module.acm_cert.certificate_arn
  error_document = "index.html"
  index_document = "index.html"

  custom_error_response = [
    {
        "error_code"         = 404
        "response_code"      = 200
        "response_page_path" = "/index.html"
    },
    {
        "error_code"         = 403
        "response_code"      = 200
        "response_page_path" = "/index.html"
    },
  ]

  tags = var.tags
}

data "aws_route53_zone" "base" {
  name = var.zone_name
}

resource "aws_route53_record" "this" {
  zone_id = data.aws_route53_zone.base.zone_id
  name    = var.website_domain
  type    = "A"

  alias {
    name                   = module.s3_website.domain_name
    zone_id                = module.s3_website.zone_id
    evaluate_target_health = false
  }
}

resource "aws_s3_bucket" "s3_website" {
  bucket = "foo-name"
  policy = <<POLICY
{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "PublicReadGetObject",
      "Effect": "Allow",
      "Principal": "*",
      "Action": "s3:GETObject",
      "Resource": "arn:aws:s3:::foo-name/*"
    }
  ]
}
POLICY
}

Answer 1

You'll have to modify the underlying module to make changes here.

Be sure you're aware of the impact this will have on other modules using your s3_website module. You might want to start using module source versioning.

Answer 2

If you already have your S3 bucket recognized by Terraform and it was created by the code you pasted, you schould not be having any diffculties if the operation could be done in place.

There are a few important MUST KNOW things about how TF handle resources. MUST KNOW because in the end of the day it's infrastructure :) Some of the parameters are immutable, although it might not seem that intuitive changing the resource identifier would trigger delete/create scenario.

Could you paste your TF plan output ?