JS: Add Function.getInferredName()

javascript/ql/src/semmle/javascript/Functions.qll

@@ -47,9 +47,43 @@ class Function extends @function, Parameterized, TypeParameterized, StmtContaine
   /** Gets the identifier specifying the name of this function, if any. */
   VarDecl getId() { result = getChildExpr(-1) }
 
-  /** Gets the name of this function, if any. */
+  /**
+   * Gets the name of this function, if it is a function declaration
+   * or named function expression.
+   */
   string getName() { result = getId().getName() }
 
+  /**
+   * Gets the name of this function if it has one, or a name inferred from its context.
+   *
+   * For named functions such as `function f() { ... }`, this is just the declared
+   * name. For functions assigned to variables or properties (including class
+   * members), this is the name of the variable or property. If no meaningful name
+   * can be inferred, there is no result.
+   */
+  string getInferredName() {
+    result = getName()
+    or
+    exists(VarDef vd | this = vd.getSource() |
+      result = vd.getTarget().(VarRef).getName()
+    )
+    or
+    exists(Property p |
+      this = p.getInit() and
+      result = p.getName()
+    )
+    or
+    exists(AssignExpr assign, DotExpr prop |
+      this = assign.getRhs().getUnderlyingValue() and
+      prop = assign.getLhs() and
+      result = prop.getPropertyName()
+    )
+    or
+    exists(ClassOrInterface c |
+      this = c.getMember(result).getInit()
+    )
+  }
+
   /** Gets the variable holding this function. */
   Variable getVariable() { result = getId().getVariable() }
 

javascript/ql/test/library-tests/ppNames/ppFnName.expected

@@ -1,3 +1,24 @@
+getInferredName
+| tst.js:1:1:1:15 | function f() {} | f |
+| tst.js:2:2:2:16 | function g() {} | g |
+| tst.js:4:9:4:22 | function () {} | h |
+| tst.js:5:9:5:14 | x => x | k |
+| tst.js:6:9:6:23 | function n() {} | n |
+| tst.js:9:6:9:18 | function() {} | p |
+| tst.js:10:6:10:20 | function f() {} | f |
+| tst.js:11:8:11:12 | () {} | x |
+| tst.js:12:8:12:13 | (v) {} | x |
+| tst.js:13:4:13:8 | () {} | m |
+| tst.js:17:14:17:18 | () {} | constructor |
+| tst.js:18:4:18:8 | () {} | n |
+| tst.js:22:17:22:16 | () {} | constructor |
+| tst.js:22:21:22:20 | (...arg ... rgs); } | constructor |
+| tst.js:25:17:25:16 | () {} | constructor |
+| tst.js:26:19:26:18 | () {} | constructor |
+| tst.js:27:8:27:12 | () {} | y |
+| tst.js:28:8:28:13 | (v) {} | y |
+| tst.js:31:9:31:21 | function() {} | foo |
+#select
 | tst.js:1:1:1:15 | function f() {} | function f |
 | tst.js:2:2:2:16 | function g() {} | function g |
 | tst.js:3:2:3:14 | function() {} | anonymous function |
@@ -17,3 +38,5 @@
 | tst.js:26:19:26:18 | () {} | default constructor of class G |
 | tst.js:27:8:27:12 | () {} | getter method for property y of class G |
 | tst.js:28:8:28:13 | (v) {} | setter method for property y of class G |
+| tst.js:31:9:31:21 | function() {} | method foo |
+| tst.js:32:12:32:24 | function() {} | anonymous function |

javascript/ql/test/library-tests/ppNames/ppFnName.ql

@@ -1,4 +1,8 @@
 import javascript
 
+query string getInferredName(Function f) {
+  result = f.getInferredName()
+}
+
 from Function f
 select f, f.describe()

javascript/ql/test/library-tests/ppNames/tst.js

@@ -27,3 +27,6 @@ const E = class {},       // "class E", "default constructor of class E"
   get y() {}              // "getter method for property y of class G"
   set y(v) {}             // "setter method for property y of class G"
 };
+
+o.foo = function() {};    // "method foo"
+o["Hey"] = function() {}; // "anonymous function"