temp local copy of userfunc

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

util/userfunc/public.go

@@ -0,0 +1,42 @@
+package userfunc
+
+import (
+	"github.com/hashicorp/hcl/v2"
+	"github.com/zclconf/go-cty/cty/function"
+)
+
+// A ContextFunc is a callback used to produce the base EvalContext for
+// running a particular set of functions.
+//
+// This is a function rather than an EvalContext directly to allow functions
+// to be decoded before their context is complete. This will be true, for
+// example, for applications that wish to allow functions to refer to themselves.
+//
+// The simplest use of a ContextFunc is to give user functions access to the
+// same global variables and functions available elsewhere in an application's
+// configuration language, but more complex applications may use different
+// contexts to support lexical scoping depending on where in a configuration
+// structure a function declaration is found, etc.
+type ContextFunc func() *hcl.EvalContext
+
+// DecodeUserFunctions looks for blocks of the given type in the given body
+// and, for each one found, interprets it as a custom function definition.
+//
+// On success, the result is a mapping of function names to implementations,
+// along with a new body that represents the remaining content of the given
+// body which can be used for further processing.
+//
+// The result expression of each function is parsed during decoding but not
+// evaluated until the function is called.
+//
+// If the given ContextFunc is non-nil, it will be called to obtain the
+// context in which the function result expressions will be evaluated. If nil,
+// or if it returns nil, the result expression will have access only to
+// variables named after the declared parameters. A non-nil context turns
+// the returned functions into closures, bound to the given context.
+//
+// If the returned diagnostics set has errors then the function map and
+// remain body may be nil or incomplete.
+func DecodeUserFunctions(body hcl.Body, blockType string, context ContextFunc) (funcs map[string]function.Function, remain hcl.Body, diags hcl.Diagnostics) {
+	return decodeUserFunctions(body, blockType, context)
+}