tidy up Diagnostics library

ql/src/codeql_ruby/Diagnostics.qll

@@ -2,30 +2,54 @@ private import codeql.Locations
 
 /** A diagnostic emitted during extraction, such as a parse error */
 class Diagnostic extends @diagnostic {
+  int severity;
+  string tag;
+  string message;
+  string fullMessage;
+  Location location;
+
+  Diagnostic() { diagnostics(this, severity, tag, message, fullMessage, location) }
+
   /**
    * Gets the numerical severity level associated with this diagnostic.
    */
-  int getSeverity() { diagnostics(this, result, _, _, _, _) }
+  int getSeverity() { result = severity }
+
+  /** Gets a string representation of the severity of this diagnostic. */
+  string getSeverityText() {
+    severity = 0 and result = "Hidden"
+    or
+    severity = 1 and result = "Info"
+    or
+    severity = 2 and result = "Warning"
+    or
+    severity = 3 and result = "Error"
+  }
 
   /** Gets the error code associated with this diagnostic, e.g. parse_error. */
-  string getTag() { diagnostics(this, _, result, _, _, _) }
+  string getTag() { result = tag }
 
   /**
    * Gets the error message text associated with this diagnostic.
    */
-  string getMessage() { diagnostics(this, _, _, result, _, _) }
+  string getMessage() { result = message }
 
   /**
    * Gets the full error message text associated with this diagnostic.
    */
-  string getFullMessage() { diagnostics(this, _, _, _, result, _) }
+  string getFullMessage() { result = fullMessage }
 
   /** Gets the source location of this diagnostic. */
-  Location getLocation() { diagnostics(this, _, _, _, _, result) }
+  Location getLocation() { result = location }
 
+  /** Gets a textual representation of this diagnostic. */
   string toString() { result = this.getMessage() }
 }
 
+/** A diagnostic relating to a particular error in extracting a file. */
 class ExtractionError extends Diagnostic {
-  ExtractionError() { this.getTag() = "parse_error" }
-}
+  ExtractionError() {
+    this.getSeverity() = 3 and
+    this.getTag() = "parse_error"
+  }
+}