无法在Terraform中计算“count”的值

我想创造一个 subnet route table

locals {
  aws_region = "${var.aws_regions[var.profile]}"
  base_name = "${var.product}-${local.aws_region}"
  aws_avzones = {
    pro = ["eu-west-1a", "eu-west-1b", "eu-west-1c"]
    dev = ["eu-west-2a", "eu-west-2b", "eu-west-2c"]
  }
}

# ---

# Create VPC
resource "aws_vpc" "default" {
  cidr_block = "${var.vpc_cidr_block}"

  tags = {
    Name = "${local.base_name}-vpc"
  }
}

# ---

# Create public subnets - each in a different AZ
resource "aws_subnet" "public" {
  count                   = "${length(local.aws_avzones[var.profile])}"
  vpc_id                  = "${aws_vpc.default.id}"
  cidr_block              = "${cidrsubnet(var.vpc_cidr_block, 8, count.index)}"
  availability_zone       = "${element(local.aws_avzones[var.profile], count.index)}"
  map_public_ip_on_launch = 1

  tags = {
    "Name" = "Public subnet - ${element(local.aws_avzones[var.profile], count.index)}"
  }
}

# ---

# Create Internet gateway for inbound-outbound connections
resource "aws_internet_gateway" "default" {
  vpc_id = "${aws_vpc.default.id}"

  tags = {
    "Name" = "${local.base_name}-igw"
  }
}

# ---

# Create Internet gateway routes table
resource "aws_route_table" "pub" {
  vpc_id = "${aws_vpc.default.id}"

  route {
    cidr_block = "0.0.0.0/0"
    gateway_id = "${aws_internet_gateway.default.id}"
  }

  tags = {
    Name = "${local.base_name}-rtb-igw"
  }
}

# ---

# Associate public subnets with the public route table
resource "aws_route_table_association" "pub" {
  count          = "${length(aws_subnet.public.*.id)}"
  subnet_id      = "${element(aws_subnet.public.*.id, count.index)}"
  route_table_id = "${aws_route_table.pub.id}"
}

不幸的是 terraform plan 呈现错误:

• aws\路由\表_协会.pub:aws\路由\表_协会.pub:无法计算“count”的值

为什么不能计算?Terraform并没有抱怨,当infra。当一切正常运行时,我在试图重新创建infra时,仅在销毁之后才发现此错误。

目前我的解决方法是注释掉所有 aws_route_table_association terraform apply ,取消注释,然后完成作业。显然,这离理想还很遥远。

顺便说一句,我还尝试了如下显式依赖关系声明:

resource "aws_route_table_association" "pub" {
  count          = "${length(aws_subnet.public.*.id)}"
  subnet_id      = "${element(aws_subnet.public.*.id, count.index)}"
  route_table_id = "${aws_route_table.pub.id}"

  depends_on = ["aws_subnet.public"]
}

$ terraform --version
Terraform v0.11.11
+ provider.aws v1.52.0