hclpack: fix hclpack decoding nested body

Fixes an issue where a nested block would be decoded incorrectly, the
body of the last decoded block overwrites the previously decoded ones.

This was caused by the block being assigned on the stack in the for
loop; when the block is converted to a *hcl.Block, the pointer to Body
will always point to the same block. This caused decoding a new block to
overwrite the bodies of any previously decoded blocks.

hclpack/structure.go

@@ -114,6 +114,10 @@ func (b *Body) content(schema *hcl.BodySchema, remain *Body) (*hcl.BodyContent,
 
 	var blocks []*hcl.Block
 	for _, block := range b.ChildBlocks {
+		// Redeclare block on stack so the pointer to the body is set on the
+		// correct block. https://github.com/hashicorp/hcl2/issues/72
+		block := block
+
 		blockTy := block.Type
 		blockS, wanted := blocksWanted[blockTy]
 		if !wanted {

hclpack/structure_test.go

@@ -75,6 +75,73 @@ func TestBodyContent(t *testing.T) {
 				},
 			},
 		},
+		"block attributes": {
+			&Body{
+				ChildBlocks: []Block{
+					{
+						Type: "foo",
+						Body: Body{
+							Attributes: map[string]Attribute{
+								"bar": {
+									Expr: Expression{
+										Source:     []byte(`"hello"`),
+										SourceType: ExprNative,
+									},
+								},
+							},
+						},
+					},
+					{
+						Type: "foo",
+						Body: Body{
+							Attributes: map[string]Attribute{
+								"bar": {
+									Expr: Expression{
+										Source:     []byte(`"world"`),
+										SourceType: ExprNative,
+									},
+								},
+							},
+						},
+					},
+				},
+			},
+			&hcl.BodySchema{
+				Blocks: []hcl.BlockHeaderSchema{
+					{Type: "foo"},
+				},
+			},
+			&hcl.BodyContent{
+				Blocks: hcl.Blocks{
+					{
+						Type: "foo",
+						Body: &Body{
+							Attributes: map[string]Attribute{
+								"bar": {
+									Expr: Expression{
+										Source:     []byte(`"hello"`),
+										SourceType: ExprNative,
+									},
+								},
+							},
+						},
+					},
+					{
+						Type: "foo",
+						Body: &Body{
+							Attributes: map[string]Attribute{
+								"bar": {
+									Expr: Expression{
+										Source:     []byte(`"world"`),
+										SourceType: ExprNative,
+									},
+								},
+							},
+						},
+					},
+				},
+			},
+		},
 	}
 
 	for name, test := range tests {
@@ -85,7 +152,13 @@ func TestBodyContent(t *testing.T) {
 			}
 
 			if !cmp.Equal(test.Want, got) {
-				t.Errorf("wrong result\n%s", cmp.Diff(test.Want, got))
+				bytesAsString := func(s []byte) string {
+					return string(s)
+				}
+				t.Errorf("wrong result\n%s", cmp.Diff(
+					test.Want, got,
+					cmp.Transformer("bytesAsString", bytesAsString),
+				))
 			}
 		})
 	}