add characteristic predicates to InputExpr and OutputExpr

Author: Alvaro Muñoz

ql/lib/codeql/actions/Ast.qll

@@ -96,11 +96,13 @@ class OutputsStmt extends Statement instanceof YamlMapping {
   }
 }
 
-// TODO: Needs a characteristic predicate otherwise anything is an output expression
-class InputExpr extends Expression instanceof YamlString { }
+class InputExpr extends Expression instanceof YamlString {
+  InputExpr() { exists(InputsStmt inputs | inputs.(YamlMapping).maps(this, _)) }
+}
 
-// TODO: Needs a characteristic predicate otherwise anything is an output expression
-class OutputExpr extends Expression instanceof YamlString { }
+class OutputExpr extends Expression instanceof YamlString {
+  OutputExpr() { exists(OutputsStmt outputs | outputs.(YamlMapping).maps(_, this)) }
+}
 
 /**
  * A Job is a collection of steps that run in an execution environment.

ql/lib/codeql/actions/controlflow/internal/Cfg.qll

@@ -35,11 +35,7 @@ module Completion {
 
     override string toString() { result = "BooleanCompletion(" + value + ")" }
 
-    override predicate isValidForSpecific(AstNode e) {
-      none()
-      // TODO: add support for conditional expressions?
-      //e = any(ConditionalExpression c).getCondition()
-    }
+    override predicate isValidForSpecific(AstNode e) { none() }
 
     override BooleanSuccessor getAMatchingSuccessorType() { result.getValue() = value }