Understand why TestRegress1504 does not refresh cleanly

[t0yv0]

What happened?

Introducing a test with SkipRefresh https://github.com/pulumi/pulumi-aws/compare/t0yv0/fix-1504 because refresh has changes. This is typically benign but might be interesting to investigate. This is a LaunchTemplate resource.

Example

import * as aws from "@pulumi/aws";
const ltemplate = new aws.ec2.LaunchTemplate(
    "my-launch-template",
    {
        imageId: "ami-0c55b159cbfafe1f0",
        instanceType:"t2.micro",
        keyName: 'key1',
        tags: {"Name": 'tag2'},
        updateDefaultVersion: true,
    });

Refresh diff says no changes but if pressed for details provides some:

No resources will be modified as part of this refresh; just your stack's state will be.
 details
  pulumi:pulumi:Stack: (same)
    [urn=urn:pulumi:dev::aws-3686::pulumi:pulumi:Stack::aws-3686-dev]
    ~ aws:ec2/launchTemplate:LaunchTemplate: (update)
        [id=lt-047219347b109768c]
        [urn=urn:pulumi:dev::aws-3686::aws:ec2/launchTemplate:LaunchTemplate::my-launch-template]
        [provider=urn:pulumi:dev::aws-3686::pulumi:providers:aws::default_6_32_0::1866b374-0cd7-4789-8430-daadd9035888]
        --outputs:--
      + securityGroupNames               : []
      + vpcSecurityGroupIds              : []

This fails (which is also why we noticed this in ProgramTest):

pulumi refresh --expect-no-changes --yes                                                                                                 ~/bugs/aws-3686
Previewing refresh (dev)

View in Browser (Ctrl+O): https://app.pulumi.com/anton-pulumi-corp/aws-3686/dev/previews/d5d294f9-a1c4-462b-8f5c-95a4782d45a4

     Type                       Name                Plan       Info
     pulumi:pulumi:Stack        aws-3686-dev                   
 ~   └─ aws:ec2:LaunchTemplate  my-launch-template  update     [diff: +securityGroupNames,vpcSecurityGroupIds]

Resources:
    ~ 1 to update
    1 unchanged

Refreshing (dev)

View in Browser (Ctrl+O): https://app.pulumi.com/anton-pulumi-corp/aws-3686/dev/updates/6

     Type                       Name                Status              Info
     pulumi:pulumi:Stack        aws-3686-dev                            
 ~   └─ aws:ec2:LaunchTemplate  my-launch-template  updated (0.71s)     [diff: +securityGroupNames,vpcSecurityGroupIds]

Resources:
    ~ 1 updated
    1 unchanged

Duration: 2s

error: error: no changes were expected but changes occurred

If I do pulumi up --refresh then the program corrects itself; notably it does not show any changes.

If I do pulumi --refresh --yes this also fixes itself subsequently.

Output of pulumi about

N/A

Additional context

N/A

Contributing

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[t0yv0]

In TF this program also has state changes upon refresh, but since TF implies refresh on apply, this quickly auto-corrects itself:

resource "aws_launch_template" "lt" {
  image_id = "ami-0c55b159cbfafe1f0"
  instance_type = "t2.micro"
  key_name = "key1"
  update_default_version = true
}

First state:

# aws_launch_template.lt:
resource "aws_launch_template" "lt" {
    arn                     = "arn:aws:ec2:us-east-1:616138583583:launch-template/lt-034fd5d51ac15a63c"
    default_version         = 1
    disable_api_stop        = false
    disable_api_termination = false
    id                      = "lt-034fd5d51ac15a63c"
    image_id                = "ami-0c55b159cbfafe1f0"
    instance_type           = "t2.micro"
    key_name                = "key1"
    latest_version          = 1
    name                    = "terraform-20240424222151918500000001"
    name_prefix             = "terraform-"
    tags_all                = {}
    update_default_version  = true
}

second state:

# aws_launch_template.lt:
resource "aws_launch_template" "lt" {
    arn                     = "arn:aws:ec2:us-east-1:616138583583:launch-template/lt-034fd5d51ac15a63c"
    default_version         = 1
    disable_api_stop        = false
    disable_api_termination = false
    id                      = "lt-034fd5d51ac15a63c"
    image_id                = "ami-0c55b159cbfafe1f0"
    instance_type           = "t2.micro"
    key_name                = "key1"
    latest_version          = 1
    name                    = "terraform-20240424222151918500000001"
    name_prefix             = "terraform-"
    security_group_names    = []
    tags                    = {}
    tags_all                = {}
    update_default_version  = true
    vpc_security_group_ids  = []
}