feat(ivy): ngcc - support ngcc "migrations" (#31544)

This commit implements support for the ngcc migrations
as designed in https://hackmd.io/KhyrFV1VQHmeQsgfJq6AyQ

PR Close #31544

packages/compiler-cli/ngcc/src/analysis/migration_host.ts

@@ -0,0 +1,81 @@
+/**
+ * @license
+ * Copyright Google Inc. 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 ts from 'typescript';
+import {ErrorCode, FatalDiagnosticError} from '../../../src/ngtsc/diagnostics';
+import {MetadataReader} from '../../../src/ngtsc/metadata';
+import {PartialEvaluator} from '../../../src/ngtsc/partial_evaluator';
+import {ClassDeclaration, Decorator} from '../../../src/ngtsc/reflection';
+import {DecoratorHandler} from '../../../src/ngtsc/transform';
+import {NgccReflectionHost} from '../host/ngcc_host';
+import {MigrationHost} from '../migrations/migration';
+import {AnalyzedClass, AnalyzedFile} from './types';
+import {analyzeDecorators} from './util';
+
+/**
+ * The standard implementation of `MigrationHost`, which is created by the
+ * `DecorationAnalyzer`.
+ */
+export class DefaultMigrationHost implements MigrationHost {
+  constructor(
+      readonly reflectionHost: NgccReflectionHost, readonly metadata: MetadataReader,
+      readonly evaluator: PartialEvaluator, private handlers: DecoratorHandler<any, any>[],
+      private analyzedFiles: AnalyzedFile[]) {}
+
+  injectSyntheticDecorator(clazz: ClassDeclaration, decorator: Decorator): void {
+    const classSymbol = this.reflectionHost.getClassSymbol(clazz) !;
+    const newAnalyzedClass = analyzeDecorators(classSymbol, [decorator], this.handlers);
+    if (newAnalyzedClass === null) {
+      return;
+    }
+
+    const analyzedFile = getOrCreateAnalyzedFile(this.analyzedFiles, clazz.getSourceFile());
+    const oldAnalyzedClass = analyzedFile.analyzedClasses.find(c => c.declaration === clazz);
+    if (oldAnalyzedClass === undefined) {
+      analyzedFile.analyzedClasses.push(newAnalyzedClass);
+    } else {
+      mergeAnalyzedClasses(oldAnalyzedClass, newAnalyzedClass);
+    }
+  }
+}
+
+function getOrCreateAnalyzedFile(
+    analyzedFiles: AnalyzedFile[], sourceFile: ts.SourceFile): AnalyzedFile {
+  const analyzedFile = analyzedFiles.find(file => file.sourceFile === sourceFile);
+  if (analyzedFile !== undefined) {
+    return analyzedFile;
+  } else {
+    const newAnalyzedFile: AnalyzedFile = {sourceFile, analyzedClasses: []};
+    analyzedFiles.push(newAnalyzedFile);
+    return newAnalyzedFile;
+  }
+}
+
+function mergeAnalyzedClasses(oldClass: AnalyzedClass, newClass: AnalyzedClass) {
+  if (newClass.decorators !== null) {
+    if (oldClass.decorators === null) {
+      oldClass.decorators = newClass.decorators;
+    } else {
+      for (const newDecorator of newClass.decorators) {
+        if (oldClass.decorators.some(d => d.name === newDecorator.name)) {
+          throw new FatalDiagnosticError(
+              ErrorCode.NGCC_MIGRATION_DECORATOR_INJECTION_ERROR, newClass.declaration,
+              `Attempted to inject "${newDecorator.name}" decorator over a pre-existing decorator with the same name on the "${newClass.name}" class.`);
+        }
+      }
+      oldClass.decorators.push(...newClass.decorators);
+    }
+  }
+
+  if (newClass.diagnostics !== undefined) {
+    if (oldClass.diagnostics === undefined) {
+      oldClass.diagnostics = newClass.diagnostics;
+    } else {
+      oldClass.diagnostics.push(...newClass.diagnostics);
+    }
+  }
+}