1 files changed, 68 insertions, 0 deletions

diff --git a/vendor/github.com/hashicorp/hcl2/hcl/expr_unwrap.go b/vendor/github.com/hashicorp/hcl2/hcl/expr_unwrap.go
new file mode 100644
index 0000000..6d5d205
--- /dev/null
+++ b/vendor/github.com/hashicorp/hcl2/hcl/expr_unwrap.go
@@ -0,0 +1,68 @@
+package hcl
+
+type unwrapExpression interface {
+        UnwrapExpression() Expression
+}
+
+// UnwrapExpression removes any "wrapper" expressions from the given expression,
+// to recover the representation of the physical expression given in source
+// code.
+//
+// Sometimes wrapping expressions are used to modify expression behavior, e.g.
+// in extensions that need to make some local variables available to certain
+// sub-trees of the configuration. This can make it difficult to reliably
+// type-assert on the physical AST types used by the underlying syntax.
+//
+// Unwrapping an expression may modify its behavior by stripping away any
+// additional constraints or capabilities being applied to the Value and
+// Variables methods, so this function should generally only be used prior
+// to operations that concern themselves with the static syntax of the input
+// configuration, and not with the effective value of the expression.
+//
+// Wrapper expression types must support unwrapping by implementing a method
+// called UnwrapExpression that takes no arguments and returns the embedded
+// Expression. Implementations of this method should peel away only one level
+// of wrapping, if multiple are present. This method may return nil to
+// indicate _dynamically_ that no wrapped expression is available, for
+// expression types that might only behave as wrappers in certain cases.
+func UnwrapExpression(expr Expression) Expression {
+        for {
+                unwrap, wrapped := expr.(unwrapExpression)
+                if !wrapped {
+                        return expr
+                }
+                innerExpr := unwrap.UnwrapExpression()
+                if innerExpr == nil {
+                        return expr
+                }
+                expr = innerExpr
+        }
+}
+
+// UnwrapExpressionUntil is similar to UnwrapExpression except it gives the
+// caller an opportunity to test each level of unwrapping to see each a
+// particular expression is accepted.
+//
+// This could be used, for example, to unwrap until a particular other
+// interface is satisfied, regardless of wrap wrapping level it is satisfied
+// at.
+//
+// The given callback function must return false to continue wrapping, or
+// true to accept and return the proposed expression given. If the callback
+// function rejects even the final, physical expression then the result of
+// this function is nil.
+func UnwrapExpressionUntil(expr Expression, until func(Expression) bool) Expression {
+        for {
+                if until(expr) {
+                        return expr
+                }
+                unwrap, wrapped := expr.(unwrapExpression)
+                if !wrapped {
+                        return nil
+                }
+                expr = unwrap.UnwrapExpression()
+                if expr == nil {
+                        return nil
+                }
+        }
+}