json: verify that objects have keys [GH-128]

json/parser/parser.go

@@ -128,6 +128,12 @@ func (p *Parser) objectKey() ([]*ast.ObjectKey, error) {
 				Token: p.tok.HCLToken(),
 			})
 		case token.COLON:
+			// If we have a zero keycount it means that we never got
+			// an object key, i.e. `{ :`. This is a syntax error.
+			if keyCount == 0 {
+				return nil, fmt.Errorf("expected: STRING got: %s", p.tok.Type)
+			}
+
 			// Done
 			return keys, nil
 		case token.ILLEGAL:

json/parser/parser_test.go

@@ -311,6 +311,10 @@ func TestParse(t *testing.T) {
 			"types.json",
 			false,
 		},
+		{
+			"bad_input_128.json",
+			true,
+		},
 	}
 
 	const fixtureDir = "./test-fixtures"

json/parser/test-fixtures/bad_input_128.json

@@ -0,0 +1 @@
+{:{