ng add @angular/material 失败并显示“无法读取 null 的属性‘endTag’”？

Question

我正在尝试将 Angular Material 添加到我的 Angular 9 项目中，以便我可以使用自动完成功能。不幸的是，在遵循安装指南时，我无法完成安装 Angular Material 模块的第一步。我尝试按照此stackoverflow 帖子中列出的步骤解决该问题。这是我采取的步骤，下面是我的 package.json 供参考。

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1. npm install --save @angular/material @angular/cdk @angular/animations
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2. ng add @angular/material
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这些命令的输出如下：

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chantelle@penny:~/projects/nereus_bos/2020-bos-frontend/bos-frontend$ npm install @angular/material --save\nnpm WARN @aws-amplify/datastore@2.1.0 requires a peer of @react-native-community/netinfo@^5.5.0 but none is installed. You must install peer dependencies yourself.\nnpm WARN @aws-amplify/core@2.3.0 requires a peer of @react-native-community/netinfo@^5.5.0 but none is installed. You must install peer dependencies yourself.\nnpm WARN optional SKIPPING OPTIONAL DEPENDENCY: fsevents@2.1.3 (node_modules/fsevents):\nnpm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for fsevents@2.1.3: wanted {"os":"darwin","arch":"any"} (current: {"os":"linux","arch":"x64"})\nnpm WARN optional SKIPPING OPTIONAL DEPENDENCY: fsevents@1.2.13 (node_modules/watchpack-chokidar2/node_modules/fsevents):\nnpm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for fsevents@1.2.13: wanted {"os":"darwin","arch":"any"} (current: {"os":"linux","arch":"x64"})\nnpm WARN optional SKIPPING OPTIONAL DEPENDENCY: fsevents@1.2.13 (node_modules/webpack-dev-server/node_modules/fsevents):\nnpm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for fsevents@1.2.13: wanted {"os":"darwin","arch":"any"} (current: {"os":"linux","arch":"x64"})\n\n+ @angular/material@9.2.4\nupdated 1 package and audited 1729 packages in 10.141s\n\n54 packages are looking for funding\n  run `npm fund` for details\n\nfound 1 low severity vulnerability\n  run `npm audit fix` to fix them, or `npm audit` for details\n\nchantelle@penny:~/projects/nereus_bos/2020-bos-frontend/bos-frontend$ ng add @angular/material\nSkipping installation: Package already installed\n? Choose a prebuilt theme name, or "custom" for a custom theme: Deep Purple/Amber  [ Preview: https://material.angular.io?theme=deepp\nurple-amber ]\n? Set up global Angular Material typography styles? No\n? Set up browser animations for Angular Material? Yes\nUPDATE package.json (1563 bytes)\n\xe2\x9c\x94 Packages installed successfully.\nCannot read property \'endTag\' of null\n

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我的package.json：

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{\n  "name": "bos-frontend",\n  "version": "0.0.0",\n  "scripts": {\n    "ng": "ng",\n    "start": "ng serve",\n    "build": "ng build",\n    "test": "ng test",\n    "lint": "ng lint",\n    "e2e": "ng e2e"\n  },\n  "private": true,\n  "dependencies": {\n    "@angular/animations": "^9.1.9",\n    "@angular/cdk": "^9.2.4",\n    "@angular/common": "~9.1.9",\n    "@angular/compiler": "~9.1.9",\n    "@angular/core": "~9.1.9",\n    "@angular/forms": "~9.1.9",\n    "@angular/localize": "~9.1.7",\n    "@angular/material": "^9.2.4",\n    "@angular/platform-browser": "~9.1.9",\n    "@angular/platform-browser-dynamic": "~9.1.9",\n    "@angular/router": "~9.1.9",\n    "@aws-amplify/pubsub": "^2.1.1",\n    "@ng-bootstrap/ng-bootstrap": "^6.1.0",\n    "aws-amplify": "^3.0.11",\n    "bootstrap": "^4.5.0",\n    "jquery": "^3.5.1",\n    "ngx-spinner": "^9.0.2",\n    "popper.js": "^1.16.1",\n    "rxjs": "~6.5.4",\n    "tslib": "^1.10.0",\n    "zone.js": "~0.10.2"\n  },\n  "devDependencies": {\n    "@angular-devkit/build-angular": "~0.901.7",\n    "@angular/cli": "~9.1.7",\n    "@angular/compiler-cli": "~9.1.9",\n    "@types/node": "^12.11.1",\n    "@types/jasmine": "~3.5.0",\n    "@types/jasminewd2": "~2.0.3",\n    "codelyzer": "^5.1.2",\n    "jasmine-core": "~3.5.0",\n    "jasmine-spec-reporter": "~4.2.1",\n    "karma": "~5.0.0",\n    "karma-chrome-launcher": "~3.1.0",\n    "karma-coverage-istanbul-reporter": "~2.1.0",\n    "karma-jasmine": "~3.0.1",\n    "karma-jasmine-html-reporter": "^1.4.2",\n    "protractor": "~5.4.3",\n    "ts-node": "~8.3.0",\n    "tslint": "~6.1.0",\n    "typescript": "~3.8.3"\n  }\n}\n

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Answer 1

该错误可能是由重复的结束标记引起的。

检查您的 .html 文件，删除重复的结束标记，例如</html>,</body>.