QL code and tests for C#/C++/JavaScript.

cpp/ql/src/Documentation/UncommentedFunction.ql

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+/**
+ * @name Poorly documented large function
+ * @description Large functions that have no or almost no comments are likely to be too complex to understand and maintain. The larger a function is, the more problematic the lack of comments.
+ * @kind problem
+ * @problem.severity warning
+ * @precision medium
+ * @id cpp/poorly-documented-function
+ * @tags maintainability
+ *       documentation
+ *       statistical
+ *       non-attributable
+ */
+import cpp
+
+from MetricFunction f, int n
+where n = f.getNumberOfLines() and n > 100 and
+      f.getCommentRatio() <= 0.02 and
+      not f.isMultiplyDefined()
+select f, "Poorly documented function: fewer than 2% comments for a function of " + n.toString() + " lines."