Ruby: Split basic blocks around constant conditionals

Author: hvitved

ruby/ql/lib/codeql/ruby/controlflow/BasicBlocks.qll

@@ -252,6 +252,30 @@ private module Cached {
     cfn.isJoin()
     or
     cfn.getAPredecessor().isBranch()
+    or
+    /*
+     * In cases such as
+     *
+     * ```rb
+     * if x or y
+     *     foo
+     * else
+     *     bar
+     * ```
+     *
+     * we have a CFG that looks like
+     *
+     * x --false--> [false] x or y --false--> bar
+     * \                    |
+     *  --true--> y --false--
+     *            \
+     *             --true--> [true] x or y --true--> foo
+     *
+     * and we want to ensure that both `foo` and `bar` start a new basic block,
+     * in order to get a `ConditionalBlock` out of the disjunction.
+     */
+
+    exists(cfn.getAPredecessor(any(SuccessorTypes::ConditionalSuccessor s)))
   }
 
   /**

ruby/ql/test/library-tests/dataflow/barrier-guards/barrier-guards.expected

@@ -49,4 +49,8 @@ controls
 | barrier-guards.rb:100:4:100:21 | call to include? | barrier-guards.rb:103:5:103:7 | foo | false |
 | barrier-guards.rb:106:4:106:4 | call to x | barrier-guards.rb:106:4:106:9 | [false] ... or ... | false |
 | barrier-guards.rb:106:4:106:4 | call to x | barrier-guards.rb:106:9:106:9 | self | false |
+| barrier-guards.rb:106:4:106:4 | call to x | barrier-guards.rb:109:5:109:7 | foo | false |
+| barrier-guards.rb:106:4:106:9 | [false] ... or ... | barrier-guards.rb:109:5:109:7 | foo | false |
+| barrier-guards.rb:106:4:106:9 | [true] ... or ... | barrier-guards.rb:107:5:107:7 | foo | true |
 | barrier-guards.rb:106:9:106:9 | call to y | barrier-guards.rb:106:4:106:9 | [false] ... or ... | false |
+| barrier-guards.rb:106:9:106:9 | call to y | barrier-guards.rb:109:5:109:7 | foo | false |