Add AlertSuppression.ql

ql/src/AlertSuppression.ql

@@ -0,0 +1,82 @@
+/**
+ * @name Alert suppression
+ * @description Generates information about alert suppressions.
+ * @kind alert-suppression
+ * @id rb/alert-suppression
+ */
+
+import ruby
+import codeql.ruby.ast.internal.TreeSitter
+
+/**
+ * An alert suppression comment.
+ */
+class SuppressionComment extends Ruby::Comment {
+  string annotation;
+
+  SuppressionComment() {
+    // suppression comments must be single-line
+    this.getLocation().getStartLine() = this.getLocation().getEndLine() and
+    exists(string text | text = commentText(this) |
+      // match `lgtm[...]` anywhere in the comment
+      annotation = text.regexpFind("(?i)\\blgtm\\s*\\[[^\\]]*\\]", _, _)
+      or
+      // match `lgtm` at the start of the comment and after semicolon
+      annotation = text.regexpFind("(?i)(?<=^|;)\\s*lgtm(?!\\B|\\s*\\[)", _, _).trim()
+    )
+  }
+
+  /**
+   * Gets the text of this suppression comment.
+   */
+  string getText() { result = commentText(this) }
+
+  /** Gets the suppression annotation in this comment. */
+  string getAnnotation() { result = annotation }
+
+  /**
+   * Holds if this comment applies to the range from column `startcolumn` of line `startline`
+   * to column `endcolumn` of line `endline` in file `filepath`.
+   */
+  predicate covers(string filepath, int startline, int startcolumn, int endline, int endcolumn) {
+    this.getLocation().hasLocationInfo(filepath, startline, _, endline, endcolumn) and
+    startcolumn = 1
+  }
+
+  /** Gets the scope of this suppression. */
+  SuppressionScope getScope() { this = result.getSuppressionComment() }
+}
+
+private string commentText(Ruby::Comment comment) { result = comment.getValue().suffix(1) }
+
+/**
+ * The scope of an alert suppression comment.
+ */
+class SuppressionScope extends @ruby_token_comment {
+  SuppressionScope() { this instanceof SuppressionComment }
+
+  /** Gets a suppression comment with this scope. */
+  SuppressionComment getSuppressionComment() { result = this }
+
+  /**
+   * Holds if this element is at the specified location.
+   * The location spans column `startcolumn` of line `startline` to
+   * column `endcolumn` of line `endline` in file `filepath`.
+   * For more information, see
+   * [Locations](https://help.semmle.com/QL/learn-ql/ql/locations.html).
+   */
+  predicate hasLocationInfo(
+    string filepath, int startline, int startcolumn, int endline, int endcolumn
+  ) {
+    this.(SuppressionComment).covers(filepath, startline, startcolumn, endline, endcolumn)
+  }
+
+  /** Gets a textual representation of this element. */
+  string toString() { result = "suppression range" }
+}
+
+from SuppressionComment c
+select c, // suppression comment
+  c.getText(), // text of suppression comment (excluding delimiters)
+  c.getAnnotation(), // text of suppression annotation
+  c.getScope() // scope of suppression