Java: Add PrintAst

java/ql/src/printAst.ql

@@ -0,0 +1,28 @@
+/**
+ * @name Print AST
+ * @description Outputs a representation of a file's Abstract Syntax Tree. This
+ *              query is used by the VS Code extension.
+ * @id java/print-ast
+ * @kind graph
+ * @tags ide-contextual-queries/print-ast
+ */
+
+import java
+import semmle.code.java.PrintAst
+import definitions
+
+/**
+ * The source file to generate an AST from.
+ */
+external string selectedSourceFile();
+
+class PrintAstConfigurationOverride extends PrintAstConfiguration {
+  /**
+   * Holds if the location matches the selected file in the VS Code extension and
+   * the element is `fromSource`.
+   */
+  override predicate shouldPrint(Element e, Location l) {
+    super.shouldPrint(e, l) and
+    l.getFile() = getEncodedFile(selectedSourceFile())
+  }
+}

java/ql/src/semmle/code/Location.qll

@@ -86,6 +86,19 @@ class Top extends @top {
   /** Gets a textual representation of this element. */
   cached
   string toString() { hasName(this, result) }
+
+  /**
+   * Gets the name of a primary CodeQL class to which this element belongs.
+   *
+   * For most elements, this is simply the most precise syntactic category to
+   * which they belong; for example, `AddExpr` is a primary class, but
+   * `BinaryExpr` is not.
+   *
+   * This predicate always has a result. If no primary class can be
+   * determined, the result is `"???"`. If multiple primary classes match,
+   * this predicate can have multiple results.
+   */
+  string getAPrimaryQlClass() { result = "???" }
 }
 
 /** A location maps language elements to positions in source files. */

java/ql/src/semmle/code/java/Annotation.qll

@@ -72,6 +72,8 @@ class Annotation extends @annotation, Expr {
       if value instanceof ArrayInit then result = value.(ArrayInit).getAnInit() else result = value
     )
   }
+
+  override string getAPrimaryQlClass() { result = "Annotation" }
 }
 
 /** An `Annotation` that applies to a declaration. */

java/ql/src/semmle/code/java/CompilationUnit.qll

@@ -30,4 +30,6 @@ class CompilationUnit extends Element, File {
    * Gets the module associated with this compilation unit, if any.
    */
   Module getModule() { cumodule(this, result) }
+
+  override string getAPrimaryQlClass() { result = "CompilationUnit" }
 }