Bug 1584538 - Allow debug environment proxy to access aliased module variables after the module script executes, r=jonco.

Differential Revision: https://phabricator.services.mozilla.com/D50747

--HG--
extra : moz-landing-system : lando

js/src/jit-test/tests/debug/Environment-module-02.js

@@ -0,0 +1,30 @@
+// Debug environments for module environments should be able to access closed
+// over variables after the module script has executed.
+
+var g = newGlobal({newCompartment: true});
+var dbg = Debugger(g);
+
+const m = g.parseModule(`
+  var x = 42;
+  export function foo() { return x; }
+  foo();
+`);
+m.declarationInstantiation();
+
+let fooFunction;
+dbg.onEnterFrame = function (frame) {
+  fooFunction = frame.callee;
+};
+
+m.evaluation();
+assertEq(fooFunction instanceof Debugger.Object, true);
+
+dbg.onEnterFrame = function (frame) {
+  const env = frame.environment.parent;
+  assertEq(env.names().join(','), "foo,x");
+  assertEq(env.getVariable('x'), 42);
+  env.setVariable('x', 3);
+  assertEq(env.getVariable('x'), 3);
+};
+
+fooFunction.call();

js/src/vm/EnvironmentObject.cpp

@@ -1497,7 +1497,6 @@ class DebugEnvironmentProxyHandler : public BaseProxyHandler {
       } else {
         script = env->as<ModuleEnvironmentObject>().module().maybeScript();
         if (!script) {
-          *accessResult = ACCESS_LOST;
           return true;
         }
       }