How to fix Error: An argument named X is not expected here. Did you mean Y? in Terraform

Update your provider locks to the latest compatible versions. This helps identify version-specific argument changes:

terraform init -upgrade

This refreshes your .terraform.lock.hcl file and downloads the latest provider versions. After this, run terraform validate to see if the issue persists or resolves.

Terraform often suggests the correct argument name. If the error says "Did you mean X?", update your configuration to use X instead.

For example, if you see:

Error: An argument named "number_cache_clusters" is not expected here. Did you mean "num_cache_clusters"?

Update your code:

# Wrong
resource "aws_elasticache_replication_group" "example" {
  number_cache_clusters = 3
}

# Correct
resource "aws_elasticache_replication_group" "example" {
  num_cache_clusters = 3
}

If you're passing arguments to a module, ensure the child module declares them as variables:

# In your root module
module "example" {
  source = "./modules/example"

  custom_argument = "value"  # ERROR: this arg must be declared in module
}

# Fix: add to modules/example/variables.tf
variable "custom_argument" {
  type        = string
  description = "Description of the argument"
}

# Then use it in the module's main.tf
resource "some_resource" "example" {
  name = var.custom_argument
}

Visit the official provider documentation and verify the argument name and type for your provider version.

For AWS Provider:
- Go to https://registry.terraform.io/providers/hashicorp/aws/latest
- Find your resource type
- Check the "Argument Reference" section for exact names

For other providers, replace aws with your provider name at https://registry.terraform.io/

If upgrading a provider, check the changelog for breaking changes or deprecated arguments:

# View provider version info
terraform version

Update your required_providers block if needed:

terraform {
  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = "~> 5.0"  # Update to desired version
    }
  }
}

Run terraform validate to catch errors early and get detailed diagnostics:

terraform validate

For more detailed error information, enable debug logging:

TF_LOG=DEBUG terraform plan 2>&1 | head -100

The full error output often shows the exact line and resource causing the issue, making it easier to pinpoint the problem.