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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.
41 lines
1.4 KiB
Go
41 lines
1.4 KiB
Go
package customdiff
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import (
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"github.com/hashicorp/terraform/helper/schema"
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)
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// ForceNewIf returns a CustomizeDiffFunc that flags the given key as
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// requiring a new resource if the given condition function returns true.
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//
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// The return value of the condition function is ignored if the old and new
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// values of the field compare equal, since no attribute diff is generated in
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// that case.
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func ForceNewIf(key string, f ResourceConditionFunc) schema.CustomizeDiffFunc {
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return func(d *schema.ResourceDiff, meta interface{}) error {
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if f(d, meta) {
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d.ForceNew(key)
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}
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return nil
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}
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}
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// ForceNewIfChange returns a CustomizeDiffFunc that flags the given key as
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// requiring a new resource if the given condition function returns true.
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//
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// The return value of the condition function is ignored if the old and new
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// values compare equal, since no attribute diff is generated in that case.
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//
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// This function is similar to ForceNewIf but provides the condition function
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// only the old and new values of the given key, which leads to more compact
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// and explicit code in the common case where the decision can be made with
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// only the specific field value.
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func ForceNewIfChange(key string, f ValueChangeConditionFunc) schema.CustomizeDiffFunc {
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return func(d *schema.ResourceDiff, meta interface{}) error {
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old, new := d.GetChange(key)
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if f(old, new, meta) {
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d.ForceNew(key)
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}
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return nil
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}
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}
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