`All()` combines the outputs of multiple `SchemaValidateFunc`, to reduce the usage of custom validation functions that implement standard validation functions.
Example provider usage:
```go
ValidateFunc: validation.All(
StringLenBetween(5, 42),
StringMatch(regexp.MustCompile(`[a-zA-Z0-9]+`), "value must be alphanumeric"),
),
```
`IntInSlice()` is the `int` equivalent of `StringInSlice()`
Example provider usage:
```go
ValidateFunc: validation.IntInSlice([]int{30, 60, 120})
```
Output from unit testing:
```
$ make test TEST=./helper/validation
==> Checking that code complies with gofmt requirements...
go generate ./...
2018/10/17 14:16:03 Generated command/internal_plugin_list.go
go list ./helper/validation | xargs -t -n4 go test -timeout=2m -parallel=4
go test -timeout=2m -parallel=4 github.com/hashicorp/terraform/helper/validation
ok github.com/hashicorp/terraform/helper/validation 1.106s
```
StringMatch returns a validation function that can be used to match a
string against a regular expression. This can be used for simple
substring validations or more complex validation scenarios. Optionally,
an error message can be returned so that the user is returned a better
error message other than that their field did not match a regular
expression that they might not be able to understand.
This adds NoZeroValues, a small SchemaValidateFunc that checks that a
defined value is not a zero value. It's useful for situations where you
want to keep someone from explicitly entering a zero value (ie:
literally "0", or an empty string) on a required field, and want to
catch it in the validation stage, versus during apply using GetOk.
Add the ValidateListUniqueStrings function, which is a ValidateFunc that
ensures a list has no duplicate items in it. It's useful for when a list
is needed over a set because order matters, yet the items still need to
be unique.
This adds a ValidateRegexp validation helper to check to see if a field
has a valid regular expression.
Includes test for good regexp, and test for bad regexp.
Brian Flad