[Bug]: Cognito User Pool: cannot modify or remove schema items

[leventyalcin]

Terraform Core Version

1.8.3

AWS Provider Version

5.54.1

Affected Resource(s)

aws_cognito_user_pool

Expected Behavior

According to this issue and the this PR, the expected behaviour of Terraform plan/apply output after the first time, updates on schema should be ignored if string_attribute_constraints is present.

Actual Behavior

I am still seeing those triggers updates on aws_cognito_user_pool and it fails with the following output error message.

Plan Output

      - schema {
          - attribute_data_type      = "String" -> null
          - developer_only_attribute = false -> null
          - mutable                  = true -> null
          - name                     = "name" -> null
          - required                 = true -> null

          - string_attribute_constraints {
              - max_length = "512" -> null
              - min_length = "1" -> null
            }
        }
      + schema {
          + attribute_data_type = "String"
          + mutable             = true
          + name                = "name"
          + required            = true

          + string_attribute_constraints {
              + max_length = "512"
              + min_length = "1"
            }
        }

Apply result

Error: updating Cognito User Pool (REGION_xxxxxxxxx): cannot modify or remove schema items

Relevant Error/Panic Output Snippet

No response

Terraform Configuration Files

resource "aws_cognito_user_pool" "pool" {
  name                = "test"
  mfa_configuration   = "OFF"
  username_attributes = ["email"]

  user_pool_add_ons {
    advanced_security_mode = "AUDIT"
  }

  schema {
    name                = "email"
    attribute_data_type = "String"
    mutable             = true
    required            = true
    string_attribute_constraints {
      min_length = 1
      max_length = 512
    }
  }

  schema {
    name                = "name"
    attribute_data_type = "String"
    mutable             = true
    required            = true
    string_attribute_constraints {
      min_length = 1
      max_length = 512
    }
  }
}

Steps to Reproduce

Terraform apply for a template contains schemas like above twice. The second apply always fail.

Debug Output

No response

Panic Output

No response

Important Factoids

No response

References

No response

Would you like to implement a fix?

None

[github-actions]

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[bannarisoftwares]

Hi @leventyalcin

Add

string_attribute_constraints {
max_length = "2048"
min_length = "0"
}
on each schema to avoid this issue

Example:

schema {
name = "scope"
attribute_data_type = "String"
mutable = true
required = false
string_attribute_constraints {
max_length = "2048"
min_length = "0"
}
}

When defining an attribute_data_type of String or Number, the respective attribute constraints configuration block (e.g string_attribute_constraints or number_attribute_constraints) is required to prevent recreation of the Terraform resource. This requirement is true for both standard (e.g., name, email) and custom schema attributes.

registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/cognito_user_pool#schema

[ewbankkit]

Relates #38096.