add a ql/path-problem-query query

Author: erik-krogh

ql/ql/src/codeql_ql/ast/internal/Module.qll

@@ -20,7 +20,18 @@ private class TFileOrModule = TFile or TModule;
 
 /** A file or a module. */
 class FileOrModule extends TFileOrModule, ContainerOrModule {
-  abstract File getFile();
+  /** Gets the module for this imported module. */
+  Module asModule() { this = TModule(result) }
+
+  /** Gets the file for this file. */
+  File asFile() { this = TFile(result) }
+
+  /** Gets the file that contains this module/file. */
+  File getFile() {
+    result = this.asFile()
+    or
+    result = this.asModule().getLocation().getFile()
+  }
 }
 
 private class File_ extends FileOrModule, TFile {
@@ -43,8 +54,6 @@ private class File_ extends FileOrModule, TFile {
     endline = 0 and
     endcolumn = 0
   }
-
-  override File getFile() { result = f }
 }
 
 private class Folder_ extends ContainerOrModule, TFolder {
@@ -94,8 +103,6 @@ class Module_ extends FileOrModule, TModule {
   ) {
     m.getLocation().hasLocationInfo(filepath, startline, startcolumn, endline, endcolumn)
   }
-
-  override File getFile() { result = m.getLocation().getFile() }
 }
 
 private predicate resolveQualifiedName(Import imp, ContainerOrModule m, int i) {

ql/ql/src/queries/bugs/PathProblemQuery.ql

@@ -0,0 +1,66 @@
+/**
+ * @name Missing edges query predicate in path-problem
+ * @description A path-problem query should have a edges relation, and a problem query should not.
+ * @kind problem
+ * @problem.severity warning
+ * @id ql/path-problem-query
+ * @tags correctness
+ *       maintainability
+ * @precision medium
+ */
+
+import ql
+import codeql_ql.ast.internal.Module
+
+FileOrModule hasEdgesRelation(ClasslessPredicate pred) {
+  pred.getName() = "edges" and
+  pred.hasAnnotation("query") and
+  (
+    result.asModule().getAMember() = pred
+    or
+    any(TopLevel top | top.getLocation().getFile() = result.asFile()).getAMember() = pred
+  )
+}
+
+FileOrModule importsEdges(ClasslessPredicate pred) {
+  result = hasEdgesRelation(pred)
+  or
+  exists(Import i |
+    not (i.hasAnnotation("private") and i.getLocation().getFile().getExtension() = "qll") and
+    importsEdges(pred) = i.getResolvedModule()
+  |
+    i = result.asModule().getAMember()
+    or
+    i = any(TopLevel top | top.getLocation().getFile() = result.asFile()).getAMember()
+  )
+}
+
+class Query extends File {
+  Query() { this.getExtension() = "ql" }
+
+  predicate isPathProblem() {
+    exists(QLDoc doc | doc.getLocation().getFile() = this |
+      doc.getContents().matches("%@kind path-problem%")
+    )
+  }
+
+  predicate isProblem() {
+    exists(QLDoc doc | doc.getLocation().getFile() = this |
+      doc.getContents().matches("%@kind problem%")
+    )
+  }
+
+  predicate hasEdgesRelation(ClasslessPredicate pred) { importsEdges(pred).asFile() = this }
+}
+
+from Query query, string msg, AstNode pred
+where
+  query.isPathProblem() and
+  not query.hasEdgesRelation(_) and
+  pred = any(TopLevel top | top.getLocation().getFile() = query) and // <- dummy value
+  msg = "A path-problem query should have a edges relation."
+  or
+  query.isProblem() and
+  query.hasEdgesRelation(pred) and
+  msg = "A problem query should not have a $@."
+select query, msg, pred, "edges relation"