Module cannot apply unless VPC has a "Name" tag

[sheax0r]

Problem Description

If the input vpc_id variable refers to a VPC that does not have a Name tag, terraform plan and terraform apply fail like this:

Error: Error refreshing state: 3 error(s) occurred:

* module.redis.aws_elasticache_parameter_group.redis_parameter_group: 1 error(s) occurred:

* module.redis.aws_elasticache_parameter_group.redis_parameter_group: At column 98, line 1: map "data.aws_vpc.vpc.tags" does not have any elements so cannot determine type. in:

${replace(format("%.255s", lower(replace("tf-redis-${var.name}-${var.env}-${data.aws_vpc.vpc.tags["Name"]}", "_", "-"))), "/\\s/", "-")}
* module.redis.aws_elasticache_subnet_group.redis_subnet_group: 1 error(s) occurred:

* module.redis.aws_elasticache_subnet_group.redis_subnet_group: At column 98, line 1: map "data.aws_vpc.vpc.tags" does not have any elements so cannot determine type. in:

${replace(format("%.255s", lower(replace("tf-redis-${var.name}-${var.env}-${data.aws_vpc.vpc.tags["Name"]}", "_", "-"))), "/\\s/", "-")}
* module.redis.aws_security_group.redis_security_group: 1 error(s) occurred:

* module.redis.aws_security_group.redis_security_group: At column 56, line 1: map "data.aws_vpc.vpc.tags" does not have any elements so cannot determine type. in:

tf-sg-ec-${var.name}-${var.env}-${data.aws_vpc.vpc.tags["Name"]}

Proposed Solution

Add a local variable, local.vpc_name, and set the value of it using coalesce so that it uses the Name tag of the VPC if it exists, or a hardcoded string like redis-vpc otherwise.

[antonbabenko]

#21 Is related to this as well.