refactor(compiler): extract save/restore view logic to separate phase (#50008)

dylhunn · alxhub · commit f780d6f20238 · 2023-05-08T14:30:13.000-07:00
Saving and restoring the view is significant enough that it makes sense to handle it independently. This makes for easier reasoning about how view save/restore works. Co-authored-by: Alex Rickabaugh <alxhub@users.noreply.github.com> PR Close #50008
diff --git a/packages/compiler/src/template/pipeline/src/emit.ts b/packages/compiler/src/template/pipeline/src/emit.ts
@@ -27,13 +27,15 @@ import {phaseVariableOptimization} from './phases/variable_optimization';
 import {phaseChaining} from './phases/chaining';
 import {phaseMergeNextContext} from './phases/next_context_merging';
 import {phaseNgContainer} from './phases/ng_container';
+import {phaseSaveRestoreView} from './phases/save_restore_view';
 
 /**
  * Run all transformation phases in the correct order against a `ComponentCompilation`. After this
  * processing, the compilation should be in a state where it can be emitted via `emitTemplateFn`.s
  */
 export function transformTemplate(cpl: ComponentCompilation): void {
   phaseGenerateVariables(cpl);
+  phaseSaveRestoreView(cpl);
   phaseResolveNames(cpl);
   phaseResolveContexts(cpl);
   phaseLocalRefs(cpl);
diff --git a/packages/compiler/src/template/pipeline/src/phases/generate_variables.ts b/packages/compiler/src/template/pipeline/src/phases/generate_variables.ts
@@ -40,12 +40,11 @@ function recursivelyProcessView(view: ViewCompilation, parentScope: Scope|null):
   // Extract a `Scope` from this view.
   const scope = getScopeForView(view, parentScope);
 
-  // Start the view creation block with an operation to save the current view context. This may be
-  // used to restore the view context in any listeners that may be present.
-  view.create.prepend([
-    ir.createVariableOp<ir.CreateOp>(
-        view.tpl.allocateXrefId(), scope.savedViewVariable, new ir.GetCurrentViewExpr()),
-  ]);
+  // Embedded views require an operation to save/restore the view context.
+  if (view.parent !== null) {
+    // Start the view creation block with an operation to save the current view context. This may be
+    // used to restore the view context in any listeners that may be present.
+  }
 
   for (const op of view.create) {
     switch (op.kind) {
@@ -54,26 +53,8 @@ function recursivelyProcessView(view: ViewCompilation, parentScope: Scope|null):
         recursivelyProcessView(view.tpl.views.get(op.xref)!, scope);
         break;
       case ir.OpKind.Listener:
-        // Listeners get a preamble which starts with a call to restore the view.
-        const preambleOps = [
-          ir.createVariableOp<ir.UpdateOp>(
-              view.tpl.allocateXrefId(), scope.viewContextVariable,
-              new ir.RestoreViewExpr(view.xref)),
-          // And includes all variables available to this view.
-          ...generateVariablesInScopeForView(view, scope)
-        ];
-
-        op.handlerOps.prepend(preambleOps);
-
-        // The "restore view" operation in listeners requires a call to `resetView` to reset the
-        // context prior to returning from the listener operation. Find any `return` statements in
-        // the listener body and wrap them in a call to reset the view.
-        for (const handlerOp of op.handlerOps) {
-          if (handlerOp.kind === ir.OpKind.Statement &&
-              handlerOp.statement instanceof o.ReturnStatement) {
-            handlerOp.statement.value = new ir.ResetViewExpr(handlerOp.statement.value);
-          }
-        }
+        // Prepend variables to listener handler functions.
+        op.handlerOps.prepend(generateVariablesInScopeForView(view, scope));
         break;
     }
   }
@@ -94,8 +75,6 @@ interface Scope {
 
   viewContextVariable: ir.SemanticVariable;
 
-  savedViewVariable: ir.SemanticVariable;
-
   contextVariables: Map<string, ir.SemanticVariable>;
 
   /**
@@ -148,11 +127,6 @@ function getScopeForView(view: ViewCompilation, parent: Scope|null): Scope {
       name: null,
       view: view.xref,
     },
-    savedViewVariable: {
-      kind: ir.SemanticVariableKind.SavedView,
-      name: null,
-      view: view.xref,
-    },
     contextVariables: new Map<string, ir.SemanticVariable>(),
     references: [],
     parent,
diff --git a/packages/compiler/src/template/pipeline/src/phases/save_restore_view.ts b/packages/compiler/src/template/pipeline/src/phases/save_restore_view.ts
@@ -0,0 +1,56 @@
+/**
+ * @license
+ * Copyright Google LLC All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+import * as o from '../../../../output/output_ast';
+import * as ir from '../../ir';
+import type {ComponentCompilation} from '../compilation';
+
+export function phaseSaveRestoreView(cpl: ComponentCompilation): void {
+  for (const view of cpl.views.values()) {
+    if (view === cpl.root) {
+      // Save/restore operations are not necessary for the root view.
+      continue;
+    }
+
+    view.create.prepend([
+      ir.createVariableOp<ir.CreateOp>(
+          view.tpl.allocateXrefId(), {
+            kind: ir.SemanticVariableKind.SavedView,
+            name: null,
+            view: view.xref,
+          },
+          new ir.GetCurrentViewExpr()),
+    ]);
+
+    for (const op of view.create) {
+      if (op.kind !== ir.OpKind.Listener) {
+        continue;
+      }
+
+      op.handlerOps.prepend([
+        ir.createVariableOp<ir.UpdateOp>(
+            view.tpl.allocateXrefId(), {
+              kind: ir.SemanticVariableKind.Context,
+              name: null,
+              view: view.xref,
+            },
+            new ir.RestoreViewExpr(view.xref)),
+      ]);
+
+      // The "restore view" operation in listeners requires a call to `resetView` to reset the
+      // context prior to returning from the listener operation. Find any `return` statements in
+      // the listener body and wrap them in a call to reset the view.
+      for (const handlerOp of op.handlerOps) {
+        if (handlerOp.kind === ir.OpKind.Statement &&
+            handlerOp.statement instanceof o.ReturnStatement) {
+          handlerOp.statement.value = new ir.ResetViewExpr(handlerOp.statement.value);
+        }
+      }
+    }
+  }
+}
