[ddc] Reset all initialized consts on hot restart

Clear local caches storing const values in each module.

Change-Id: I7766e92df6b8d1f91bad5fbb2addb8ace7763646
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/347220
Reviewed-by: Mark Zhou <markzipan@google.com>
Reviewed-by: Sigmund Cherem <sigmund@google.com>
Commit-Queue: Nicholas Shahan <nshahan@google.com>

pkg/dev_compiler/lib/src/kernel/compiler.dart

@@ -519,8 +519,15 @@ class ProgramCompiler extends ComputeOnceConstantVisitor<js_ast.Expression>
 
     moduleItems.addAll(afterClassDefItems);
     afterClassDefItems.clear();
+    // Register the local const cache for this module so it can be cleared on a
+    // hot restart.
+    if (_constTableCache.isNotEmpty) {
+      moduleItems.add(runtimeCall('moduleConstCaches.set(#, #)', [
+        js_ast.string(_options.moduleName),
+        _constTableCache.containerId
+      ]).toStatement());
+    }
     _ticker?.logMs('Added table caches');
-
     // Add all type hierarchy rules for the interface types used in this module.
     if (_options.newRuntimeTypes) {
       // TODO(nshahan) This is likely more information than the application

sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/runtime.dart

@@ -236,6 +236,13 @@ final List<Object> _cacheMaps = JS('!', '[]');
 @notNull
 final List<void Function()> resetFields = JS('', '[]');
 
+/// A map of module ids (names) to the local const value cache in that module.
+///
+/// This is populated on module load and each cache is cleared during
+/// [hotRestart].
+@notNull
+final JSArray<Object?> moduleConstCaches = JS('!', 'new Map()');
+
 /// A counter to track each time [hotRestart] is invoked. This is used to ensure
 /// that pending callbacks that were created on a previous iteration (e.g. a
 /// timer callback or a DOM callback) will not execute when they get invoked.
@@ -254,8 +261,16 @@ void hotRestart() {
   resetFields.clear();
   for (var m in _cacheMaps) JS('', '#.clear()', m);
   _cacheMaps.clear();
+  // TODO(nshahan) Verify _nullComparisonSet isn't used with the new type system
+  // and delete.
   JS('', '#.clear()', _nullComparisonSet);
+  JS('', '#.clear()', constants);
+  JS('', '#.clear()', constantLists);
+  JS('', '#.clear()', constantSets);
   JS('', '#.clear()', constantMaps);
+
+  JS('', '#.forEach((value) => value.fill(void 0))', moduleConstCaches);
+
   if (!_ddcDeferredLoading) {
     JS('', '#.clear()', deferredImports);
   }

tests/dartdevc/hot_restart_late_test.dart

@@ -27,13 +27,22 @@ main() {
   // Read this static field first to avoid interference with other reset counts.
   var weakNullSafety = hasUnsoundNullSafety;
 
-  // TODO(42495) `Expect.throws` contains the use of a const that triggers an
-  // extra field reset but consts are not correctly reset on hot restart so the
-  // extra reset only appears once. Perform an initial Expect.throws here to
-  // avoid confusion with the reset counts later.
+  // The first call of `Expect.throws` involves type tests that initialize
+  // values in the runtime type system that will read static fields. After
+  // initialization fields are never read again (even after a hot restart)
+  // so we perform the first call here before we start counting field resets.
   Expect.throws(() => throw 'foo');
 
-  var resetFieldCount = dart.resetFields.length;
+  dart.hotRestart();
+
+  // Count the number of reset fields triggered by a call to `Expect.throws`
+  // after every hot restart. This value is used as an offset in expectations
+  // below.
+  Expect.throws(() => throw 'foo');
+  var expectThrowsResetFieldCount = dart.resetFields.length;
+  Expect.equals(1, expectThrowsResetFieldCount);
+
+  dart.hotRestart();
 
   // Set uninitialized static late fields. Avoid calling getters for these
   // statics to ensure they are reset even if they are never accessed.
@@ -62,12 +71,10 @@ main() {
   // Sound Null Safety - 6 total field resets:
   //  - 3 write/resets for the actual uninitialized field writes.
   //  - 3 reads/resets for the actual initialized field reads.
-  var expectedResets =
-      weakNullSafety ? resetFieldCount + 12 : resetFieldCount + 6;
+  var expectedResets = weakNullSafety ? 12 : 6;
   Expect.equals(expectedResets, dart.resetFields.length);
 
   dart.hotRestart();
-  resetFieldCount = dart.resetFields.length;
 
   // Late statics should throw on get when not initialized.
   Expect.throws(() => noInitializer);
@@ -95,12 +102,13 @@ main() {
   // Sound Null Safety - 6 total field resets:
   //  - 3 write/resets for the actual uninitialized field writes.
   //  - 3 reads/resets for the actual initialized field reads.
-  expectedResets = weakNullSafety ? resetFieldCount + 12 : resetFieldCount + 6;
+  expectedResets = weakNullSafety
+      ? expectThrowsResetFieldCount + 12
+      : expectThrowsResetFieldCount + 6;
   Expect.equals(expectedResets, dart.resetFields.length);
 
   dart.hotRestart();
   dart.hotRestart();
-  resetFieldCount = dart.resetFields.length;
 
   // Late statics should throw on get when not initialized.
   Expect.throws(() => noInitializer);
@@ -120,6 +128,8 @@ main() {
   // Sound Null Safety - 6 total field resets:
   //  - 3 reads/resets for actual uninitialized field reads.
   //  - 3 reads/resets for the actual initialized field reads.
-  expectedResets = weakNullSafety ? resetFieldCount + 9 : resetFieldCount + 6;
+  expectedResets = weakNullSafety
+      ? expectThrowsResetFieldCount + 9
+      : expectThrowsResetFieldCount + 6;
   Expect.equals(expectedResets, dart.resetFields.length);
 }