address conflict btw list-type attributes and ignore_changes

[br0ch0n]

fixes #9043

[Jonnymcc]

This fixes the issue in #9043 but introduces another artifact. Not only does it fix my security groups but it also lists the ebs_block_device as changing even though it is not.

 ebs_block_device.#:                                "1" => "1"
    ebs_block_device.3133358816.delete_on_termination: "true" => "true"
    ebs_block_device.3133358816.device_name:           "xvdb" => "xvdb"
    ebs_block_device.3133358816.encrypted:             "true" => "true"
    ebs_block_device.3133358816.volume_size:           "50" => "50"
    ebs_block_device.3133358816.volume_type:           "gp2" => "gp2"
    vpc_security_group_ids.#:                          "2" => "3"
    vpc_security_group_ids.2422803500:                 "sg-7656d80b" => "sg-7656d80b"
    vpc_security_group_ids.408308980:                  "sg-f175848e" => "sg-f175848e"
    vpc_security_group_ids.988224174:                  "" => "sg-75a779d"

I noticed this while debugging...
[INFO] atrrs Checking ebs_block_device.3133358816.iops, &{150 %!s(bool=true) %!s(bool=false) <nil> %!s(bool=false) %!s(bool=false) %!s(terraform.DiffAttrType=0)}, 150,

Here is the debug code,

changingSiblings := make(map[string]bool)
	for k, v := range diff.CopyAttributes() {
		log.Printf("[INFO] atrrs Checking %s, %s, %s, %s", k, v, v.Old, v.New)
		if listTypeAttrKeys[strings.Split(k, ".")[0]] && v.Old != v.New {
			changingSiblings[strings.Split(k, ".")[0]] = true
		}
	}

My guess is that since I am not specifying a number of iops it is detecting it as a change from "150" => "". Setting the iops in my TF template to 150 actually makes the reported change disappear. Should find a solution that doesn't require settings iops though.

Also, I experienced this issue by spinning up instances referencing user_data resources and later removing those resources and setting lifecyle
ignore_changes = ["user_data"]

In the meantime while waiting for this fix my workaround is to revert the changed that removed the user_data resources, that way I can remove the lifecyle changes and, as expected, I do not have the issue adding security groups anymore.

[br0ch0n]

by chance did you see if it was going to (or did) actually change your block device? Or was it purely screen spam?

[Jonnymcc]

With Terraform plan it shows as if it would modify the attribute. I did not test if it actually did.

[Jonnymcc]

It actually shows as the only change to other instances. Which leads me to believe that Terraform would always think there is a change to apply even when there is none.

[br0ch0n]

OK cool, thanks for testing! I'll try and reproduce and see what I can do.

[josephholsten]

I wonder if this is necessary after #12897

[br0ch0n]

Yaa, I should close this since it's supposedly fixed. I haven't tested personally tho.

[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.

If you have found a problem that seems similar to this, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.