fix(core): improve the "missing $localize" error message (angular#3…

…2491)

We need to be clearer to developers who upgrade to v9 (next) and get this
error, why they have a problem and what they have to do about it.

Once we have a better CLI schematics story, where this import will be
included by default in new applications and a CLI migration will add it
when upgrading apps to v9, we could simplify or remove this error message.

PR Close angular#32491

integration/side-effects/snapshots/core/esm2015.js

@@ -13,5 +13,5 @@ const __global = "undefined" !== typeof global && global;
 const _global = __globalThis || __global || __window || __self;
 
 if (ngDevMode) _global.$localize = _global.$localize || function() {
-    throw new Error("The global function `$localize` is missing. Please add `import '@angular/localize';` to your polyfills.ts file.");
+    throw new Error("It looks like your application or one of its dependencies is using i18n.\n" + "Angular 9 introduced a global `$localize()` function that needs to be loaded.\n" + "Please add `import '@angular/localize';` to your polyfills.ts file.");
 };

integration/side-effects/snapshots/core/esm5.js

@@ -15,5 +15,5 @@ var __global = "undefined" !== typeof global && global;
 var _global = __globalThis || __global || __window || __self;
 
 if (ngDevMode) _global.$localize = _global.$localize || function() {
-    throw new Error("The global function `$localize` is missing. Please add `import '@angular/localize';` to your polyfills.ts file.");
+    throw new Error("It looks like your application or one of its dependencies is using i18n.\n" + "Angular 9 introduced a global `$localize()` function that needs to be loaded.\n" + "Please add `import '@angular/localize';` to your polyfills.ts file.");
 };

packages/core/src/core.ts

@@ -45,6 +45,8 @@ if (ngDevMode) {
   // tslint:disable-next-line: no-toplevel-property-access
   global.$localize = global.$localize || function() {
     throw new Error(
-        'The global function `$localize` is missing. Please add `import \'@angular/localize\';` to your polyfills.ts file.');
+        'It looks like your application or one of its dependencies is using i18n.\n' +
+        'Angular 9 introduced a global `$localize()` function that needs to be loaded.\n' +
+        'Please add `import \'@angular/localize\';` to your polyfills.ts file.');
   };
 }