dart2js using self when it should (likely) use globalThis

[kevmoo]

These docs: https://api.dart.dev/dart-js_interop/globalContext.html

Say globalContext can be treated like JS's globalThis.

But when compiling, self is used, which blows up in Node.

Replacing self with globalThis in the output fixes issues.

Seeing this both in the use of globalContext from js_interop and with the code generated with createJSInteropWrapper

diff --git a/out.js b/out.js
index 0c4c10f..fe9f8d3 100644
--- a/out.js
+++ b/out.js
@@ -2636,7 +2636,7 @@
     },
     main() {
       A.print("Hello World!");
-      type$.JSObject._as(self).exportValue = new A.main_closure(new A.Export()).call$0();
+      type$.JSObject._as(globalThis).exportValue = new A.main_closure(new A.Export()).call$0();
     },
     main_closure: function main_closure(t0) {
       this.thing = t0;
@@ -3146,7 +3146,7 @@
     call$0() {
       var result,
         t1 = type$.JSObject,
-        t2 = t1._as(t1._as(self).Object),
+        t2 = t1._as(t1._as(globalThis).Object),
         _jsExporter = t1._as(t2.create.apply(t2, [null]));
       t2 = this.thing.get$printMessage();
       if (typeof t2 == "function")

[kevmoo]

CC @srujzs and @rakudrama

[dart-github-bot]

Summary: dart2js uses self instead of globalThis in generated JS code, causing errors in Node.js environments. Replacing self with globalThis resolves the issue.

[srujzs]

There are subtle differences depending on the compiler, but in general, globalContext can be treated like JavaScript's globalThis.

Unfortunately, you came across the subtle differences. :D Historically, package:js used self and dart.global in dart2js and ddc. When some users migrated to dart:js_interop, they saw failures in older browsers that didn't support globalThis. So, to make the migration easier, the global context that's used in every compiler is slightly different.

[sigmundch]

For context, we made the intentional change to use self here: https://dart-review.googlesource.com/c/sdk/+/319301