hcl/json/parser/flatten.go
Mitchell Hashimoto c03d57b578
json/parser: empty list value should not flatten
Fixes https://github.com/hashicorp/terraform/issues/8886

While parsing JSON, an empty list value would be assumed to be a
non-existent list of objects, and would be removed from the result. This
may have never been the correct behavior but always worked okay because
we previously didn't support lists as first class types.

With the support of lists, we need to actually return the empty list as
the type. If we return nothing, then projects like Terraform will think
that the value was never set, which is false.
2016-10-25 10:44:39 -07:00

118 lines
3.0 KiB
Go

package parser
import "github.com/hashicorp/hcl/hcl/ast"
// flattenObjects takes an AST node, walks it, and flattens
func flattenObjects(node ast.Node) {
ast.Walk(node, func(n ast.Node) (ast.Node, bool) {
// We only care about lists, because this is what we modify
list, ok := n.(*ast.ObjectList)
if !ok {
return n, true
}
// Rebuild the item list
items := make([]*ast.ObjectItem, 0, len(list.Items))
frontier := make([]*ast.ObjectItem, len(list.Items))
copy(frontier, list.Items)
for len(frontier) > 0 {
// Pop the current item
n := len(frontier)
item := frontier[n-1]
frontier = frontier[:n-1]
switch v := item.Val.(type) {
case *ast.ObjectType:
items, frontier = flattenObjectType(v, item, items, frontier)
case *ast.ListType:
items, frontier = flattenListType(v, item, items, frontier)
default:
items = append(items, item)
}
}
// Reverse the list since the frontier model runs things backwards
for i := len(items)/2 - 1; i >= 0; i-- {
opp := len(items) - 1 - i
items[i], items[opp] = items[opp], items[i]
}
// Done! Set the original items
list.Items = items
return n, true
})
}
func flattenListType(
ot *ast.ListType,
item *ast.ObjectItem,
items []*ast.ObjectItem,
frontier []*ast.ObjectItem) ([]*ast.ObjectItem, []*ast.ObjectItem) {
// If the list is empty, keep the original list
if len(ot.List) == 0 {
items = append(items, item)
return items, frontier
}
// All the elements of this object must also be objects!
for _, subitem := range ot.List {
if _, ok := subitem.(*ast.ObjectType); !ok {
items = append(items, item)
return items, frontier
}
}
// Great! We have a match go through all the items and flatten
for _, elem := range ot.List {
// Add it to the frontier so that we can recurse
frontier = append(frontier, &ast.ObjectItem{
Keys: item.Keys,
Assign: item.Assign,
Val: elem,
LeadComment: item.LeadComment,
LineComment: item.LineComment,
})
}
return items, frontier
}
func flattenObjectType(
ot *ast.ObjectType,
item *ast.ObjectItem,
items []*ast.ObjectItem,
frontier []*ast.ObjectItem) ([]*ast.ObjectItem, []*ast.ObjectItem) {
// If the list has no items we do not have to flatten anything
if ot.List.Items == nil {
items = append(items, item)
return items, frontier
}
// All the elements of this object must also be objects!
for _, subitem := range ot.List.Items {
if _, ok := subitem.Val.(*ast.ObjectType); !ok {
items = append(items, item)
return items, frontier
}
}
// Great! We have a match go through all the items and flatten
for _, subitem := range ot.List.Items {
// Copy the new key
keys := make([]*ast.ObjectKey, len(item.Keys)+len(subitem.Keys))
copy(keys, item.Keys)
copy(keys[len(item.Keys):], subitem.Keys)
// Add it to the frontier so that we can recurse
frontier = append(frontier, &ast.ObjectItem{
Keys: keys,
Assign: item.Assign,
Val: subitem.Val,
LeadComment: item.LeadComment,
LineComment: item.LineComment,
})
}
return items, frontier
}