refactor(core): change node navigation step to plain const (#59469)

We change the `enum` to a plain `const` to eliminate extra bytes, as `enum` is not really required. We might not be able to switch to `const enum` due to single-file compilation restrictions.

PR Close #59469

packages/core/src/hydration/interfaces.ts

@@ -19,11 +19,15 @@ export const REFERENCE_NODE_BODY = 'b';
 /**
  * Describes navigation steps that the runtime logic need to perform,
  * starting from a given (known) element.
+ * We're not using enum `NodeNavigationStep` because it produces more code overhead;
+ * thus, using plain `const` eliminates extra bytes. We can't use `const enum` due
+ * to single-file compilation restrictions.
  */
-export enum NodeNavigationStep {
-  FirstChild = 'f',
-  NextSibling = 'n',
-}
+
+export type NodeNavigationStep = 'f' | 'n';
+
+export const NODE_NAVIGATION_STEP_FIRST_CHILD = 'f';
+export const NODE_NAVIGATION_STEP_NEXT_SIBLING = 'n';
 
 /**
  * Keys within serialized view data structure to represent various

packages/core/src/hydration/node_lookup_utils.ts

@@ -29,6 +29,8 @@ import {
 } from './error_handling';
 import {
   DehydratedView,
+  NODE_NAVIGATION_STEP_FIRST_CHILD,
+  NODE_NAVIGATION_STEP_NEXT_SIBLING,
   NodeNavigationStep,
   NODES,
   REFERENCE_NODE_BODY,
@@ -198,7 +200,7 @@ function stringifyNavigationInstructions(instructions: (number | NodeNavigationS
     const step = instructions[i];
     const repeat = instructions[i + 1] as number;
     for (let r = 0; r < repeat; r++) {
-      container.push(step === NodeNavigationStep.FirstChild ? 'firstChild' : 'nextSibling');
+      container.push(step === NODE_NAVIGATION_STEP_FIRST_CHILD ? 'firstChild' : 'nextSibling');
     }
   }
   return container.join('.');
@@ -218,10 +220,10 @@ function navigateToNode(from: Node, instructions: (number | NodeNavigationStep)[
         throw nodeNotFoundAtPathError(from, stringifyNavigationInstructions(instructions));
       }
       switch (step) {
-        case NodeNavigationStep.FirstChild:
+        case NODE_NAVIGATION_STEP_FIRST_CHILD:
           node = node.firstChild!;
           break;
-        case NodeNavigationStep.NextSibling:
+        case NODE_NAVIGATION_STEP_NEXT_SIBLING:
           node = node.nextSibling!;
           break;
       }
@@ -279,7 +281,7 @@ export function navigateBetween(start: Node, finish: Node): NodeNavigationStep[]
       // First navigate to `finish`'s parent
       ...parentPath,
       // Then to its first child.
-      NodeNavigationStep.FirstChild,
+      NODE_NAVIGATION_STEP_FIRST_CHILD,
       // And finally from that node to `finish` (maybe a no-op if we're already there).
       ...childPath,
     ];
@@ -294,7 +296,7 @@ function navigateBetweenSiblings(start: Node, finish: Node): NodeNavigationStep[
   const nav: NodeNavigationStep[] = [];
   let node: Node | null = null;
   for (node = start; node != null && node !== finish; node = node.nextSibling) {
-    nav.push(NodeNavigationStep.NextSibling);
+    nav.push(NODE_NAVIGATION_STEP_NEXT_SIBLING);
   }
   // If the `node` becomes `null` or `undefined` at the end, that means that we
   // didn't find the `end` node, thus return `null` (which would trigger serialization

packages/core/test/bundling/hydration/bundle.golden_symbols.json

@@ -100,7 +100,6 @@
   "NodeInjector",
   "NodeInjectorDestroyRef",
   "NodeInjectorFactory",
-  "NodeNavigationStep",
   "NoneEncapsulationDomRenderer",
   "NoopNgZone",
   "NullInjector",

packages/core/test/hydration/compression_spec.ts

@@ -8,6 +8,8 @@
 
 import {compressNodeLocation, decompressNodeLocation} from '../../src/hydration/compression';
 import {
+  NODE_NAVIGATION_STEP_FIRST_CHILD,
+  NODE_NAVIGATION_STEP_NEXT_SIBLING,
   NodeNavigationStep,
   REFERENCE_NODE_BODY,
   REFERENCE_NODE_HOST,
@@ -15,8 +17,8 @@ import {
 
 describe('compression of node location', () => {
   it('should handle basic cases', () => {
-    const fc = NodeNavigationStep.FirstChild;
-    const ns = NodeNavigationStep.NextSibling;
+    const fc = NODE_NAVIGATION_STEP_FIRST_CHILD;
+    const ns = NODE_NAVIGATION_STEP_NEXT_SIBLING;
     const cases = [
       [[REFERENCE_NODE_HOST, fc, 1], 'hf'],
       [[REFERENCE_NODE_BODY, fc, 1], 'bf'],