c647b22d97
The CustomizeDiff functionality in helper/schema is powerful, but directly
writing single CustomizeDiff functions can obscure the intent when a
number of different, orthogonal diff-customization behaviors are required.
This new library provides some building blocks that aim to allow a more
declarative form of CustomizeDiff implementation, by composing a number of
smaller operations. For example:
&schema.Resource{
// ...
CustomizeDiff: customdiff.All(
customdiff.ValidateChange("size", func (old, new, meta interface{}) error {
// If we are increasing "size" then the new value must be
// a multiple of the old value.
if new.(int) <= old.(int) {
return nil
}
if (new.(int) % old.(int)) != 0 {
return fmt.Errorf("new size value must be an integer multiple of old value %d", old.(int))
}
return nil
}),
customdiff.ForceNewIfChange("size", func (old, new, meta interface{}) bool {
// "size" can only increase in-place, so we must create a new resource
// if it is decreased.
return new.(int) < old.(int)
}),
customdiff.ComputedIf("version_id", func (d *schema.ResourceDiff, meta interface{}) bool {
// Any change to "content" causes a new "version_id" to be allocated.
return d.HasChange("content")
}),
),
}
The goal is to allow the various separate operations to be quickly seen
and to ensure that each of them runs independently of the others. These
functions all create closures on the call parameters, so the result is
still just a normal CustomizeDiffFunc and so the helpers in this package
can be combined with hand-written functions as needed.
As we get more experience writing CustomizeDiff functions we may wish to
expand the repertoire of functions here in future; this initial set
attempts to cover some common cases we've seen so far. We may also
investigate some helper functions that are entirely declarative and so
don't take callback functions at all, but want to learn what the relevant
use-cases are before going in too deep here.
|
||
|---|---|---|
| .. | ||
| acctest | ||
| config | ||
| copy | ||
| customdiff | ||
| didyoumean | ||
| diff | ||
| encryption | ||
| experiment | ||
| hashcode | ||
| hilmapstructure | ||
| logging | ||
| mutexkv | ||
| pathorcontents | ||
| resource | ||
| schema | ||
| shadow | ||
| signalwrapper | ||
| slowmessage | ||
| structure | ||
| validation | ||
| variables | ||
| wrappedreadline | ||
| wrappedstreams | ||
| README.md | ||
README.md
Helper Libraries
This folder contains helper libraries for Terraform plugins. A running joke is that this is "Terraform standard library" for plugins. The goal of the packages in this directory are to provide high-level helpers to make it easier to implement the various aspects of writing a plugin for Terraform.