QL: Add support for YAML comments.

Author: MathiasVP

ql/ql/src/codeql_ql/ast/Ast.qll

@@ -2737,6 +2737,12 @@ module YAML {
     class ParseErrorBase extends LocatableBase, @yaml_error {
       string getMessage() { yaml_errors(this, result) }
     }
+
+    class CommentBase extends LocatableBase, @yaml_comment {
+      string getText() { yaml_comments(this, result, _) }
+
+      override string toString() { yaml_comments(this, _, result) }
+    }
   }
 
   import LibYaml::Make<YamlSig>

ql/ql/src/codeql_ql/ast/Yaml.qll

@@ -46,6 +46,12 @@ private module YamlSig implements LibYaml::InputSig {
   class ParseErrorBase extends LocatableBase, @yaml_error {
     string getMessage() { yaml_errors(this, result) }
   }
+
+  class CommentBase extends LocatableBase, @yaml_comment {
+    string getText() { yaml_comments(this, result, _) }
+
+    override string toString() { yaml_comments(this, _, result) }
+  }
 }
 
 import LibYaml::Make<YamlSig>

ql/ql/src/ql.dbscheme

@@ -101,13 +101,17 @@ yaml_scalars (unique int scalar: @yaml_scalar_node ref,
               int style: int ref,
               string value: string ref);
 
+yaml_comments (unique int id: @yaml_comment,
+               string text: string ref,
+               string tostring: string ref);
+
 yaml_errors (unique int id: @yaml_error,
              string message: string ref);
 
 yaml_locations(unique int locatable: @yaml_locatable ref,
              int location: @location_default ref);
 
-@yaml_locatable = @yaml_node | @yaml_error;
+@yaml_locatable = @yaml_node | @yaml_error | @yaml_comment;
 
 /*- Database metadata -*/