aws_elasticache_cluster maintenance_window always wants to reapply if value is not lowercase

[abevoelker]

I have this in my main.tf:

resource "aws_elasticache_cluster" "foo" {
    // ...
    maintenance_window = "Tue:09:00-Tue:10:00"
}

which causes terraform plan to always want to change it every time I run it:

~ aws_elasticache_cluster.foo
    maintenance_window: "tue:09:00-tue:10:00" => "Tue:09:00-Tue:10:00"

When I change the value in main.tf to be lowercase (maintenance_window = "tue:09:00-tue:10:00") the problem is resolved.

The aws_elasticache_cluster docs do use a lowercase example for maintenance_window, however the aws_db_instance (RDS) example does not (which is what I had implemented first so I cribbed from that). However, this issue doesn't occur with aws_db_instance; that seems to be because it was fixed in #2719.

[stack72]

@jen20 @abevoelker fixed in #4020

[ghost]

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