ComputedIf deletes diff key with same prefix

[rick-masters]

SDK version

2.4.4

Relevant Provider Source Code

        CustomizeDiff: customdiff.Sequence(
            customdiff.ComputedIf("private_ips", func(_ context.Context, diff *schema.ResourceDiff, meta interface{}) bool {
                return diff.HasChange("private_ips_count")
            }),
        ),

Applied to this resource: https://github.com/hashicorp/terraform-provider-aws/blob/main/aws/resource_aws_network_interface.go

This functionality helps resolve issue hashicorp/terraform-provider-aws#9277 in the AWS provider as suggested here hashicorp/terraform-provider-aws#9277 (comment)

Terraform Configuration Files

resource "aws_network_interface" "test_iface" {
    subnet_id        = "subnet-redacted"
    private_ips_count = 4
    security_groups = ["sg-redacted"]
}

Debug Output

N/A

Expected Behavior

If private_ips_count is changed, private_ips should be computed.

Actual Behavior

If private_ips_count is changed, private_ips is computed but private_ips_count has its pending change deleted.

Steps

terraform init
terraform apply
# Change private_ips_count
terraform apply

Reference

The root cause of this problem is that clear(key string) in helper/schema/resource_diff.go is using strings.HasPrefix to delete nested keys but incorrectly finds overlapping plain keys. There is another function in resource_diff.go matching the same way.

[dd-willgan]

@rick-masters Thanks so much for detailing this, had the same issue!

[github-actions]

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