refactor(core): add assertion to avoid writes to directive factories (#59980)

crisbeto · thePunderWoman · commit fa260a98623e · 2025-02-18T19:28:01.000Z
Attempting to write to directive inputs before the directive is created can lead to subtle issues that won't necessarily trigger errors. These changes add an assertion to catch such issues earlier. PR Close #59980
diff --git a/packages/core/src/render3/instructions/write_to_directive_input.ts b/packages/core/src/render3/instructions/write_to_directive_input.ts
@@ -13,6 +13,7 @@ import {InputSignalNode} from '../../authoring/input/input_signal_node';
 import {applyValueToInputField} from '../apply_value_input_field';
 import {DirectiveDef} from '../interfaces/definition';
 import {InputFlags} from '../interfaces/input_flags';
+import {isFactory} from '../interfaces/injector';
 
 export function writeToDirectiveInput<T>(
   def: DirectiveDef<T>,
@@ -22,10 +23,21 @@ export function writeToDirectiveInput<T>(
 ) {
   const prevConsumer = setActiveConsumer(null);
   try {
-    if (ngDevMode && !def.inputs.hasOwnProperty(publicName)) {
-      throw new Error(
-        `ASSERTION ERROR: Directive ${def.type.name} does not have an input with a public name of "${publicName}"`,
-      );
+    if (ngDevMode) {
+      if (!def.inputs.hasOwnProperty(publicName)) {
+        throw new Error(
+          `ASSERTION ERROR: Directive ${def.type.name} does not have an input with a public name of "${publicName}"`,
+        );
+      }
+
+      // Usually we resolve the directive instance using `LView[someIndex]` before writing to an
+      // input, however if the read happens to early, the `LView[someIndex]` might actually be a
+      // `NodeInjectorFactory`. Check for this specific case here since it can break in subtle ways.
+      if (isFactory(instance)) {
+        throw new Error(
+          `ASSERTION ERROR: Cannot write input to factory for type ${def.type.name}. Directive has not been created yet.`,
+        );
+      }
     }
 
     const [privateName, flags, transform] = def.inputs[publicName];
