TypeError 中的错误：无法读取未定义的属性“标志”

Question

当我尝试ng serve在最近创建的 Angular 项目上运行时遇到问题。我使用的版本是 9.1.4，这个错误不会发生在一个旧的 Angular 版本的项目上。

Package                           Version
-----------------------------------------------------------
@angular-devkit/architect         0.901.4
@angular-devkit/build-angular     0.901.4
@angular-devkit/build-optimizer   0.901.4
@angular-devkit/build-webpack     0.901.4
@angular-devkit/core              9.1.4
@angular-devkit/schematics        9.1.4
@angular/cli                      9.1.4
@ngtools/webpack                  9.1.4
@schematics/angular               9.1.4
@schematics/update                0.901.4
rxjs                              6.5.5
typescript                        3.8.3
webpack                           4.42.0

执行后ng serve或ng build：

chunk {main} main.js, main.js.map (main) 2 kB [initial] [rendered]<br>
chunk {polyfills} polyfills.js, polyfills.js.map (polyfills) 679 bytes [initial] [rendered]<br>
chunk {runtime} runtime.js, runtime.js.map (runtime) 6.15 kB [entry] [rendered]<br>
chunk {styles} styles.js, styles.js.map (styles) 12.4 kB [initial] [rendered]<br>
chunk {vendor} vendor.js, vendor.js.map (vendor) 339 kB [initial] [rendered]<br>
Date: 2020-05-08T02:06:46.145Z - Hash: 1a1b937f0ca2bb37634b - Time: 4087ms<br>

**ERROR in TypeError: Cannot read property 'flags' of undefined**
    at resolveAlias (C:\Cursos\Angular\ang-hello-world\node_modules\typescript\lib\typescript.js:36513:37)
    at checkAliasSymbol (C:\Cursos\Angular\ang-hello-world\node_modules\typescript\lib\typescript.js:64502:26)
    at checkImportBinding (C:\Cursos\Angular\ang-hello-world\node_modules\typescript\lib\typescript.js:64534:13)
    at checkImportDeclaration (C:\Cursos\Angular\ang-hello-world\node_modules\typescript\lib\typescript.js:64552:29)
    at checkSourceElementWorker (C:\Cursos\Angular\ang-hello-world\node_modules\typescript\lib\typescript.js:64961:28)
    at checkSourceElement (C:\Cursos\Angular\ang-hello-world\node_modules\typescript\lib\typescript.js:64800:17)
    at Object.forEach (C:\Cursos\Angular\ang-hello-world\node_modules\typescript\lib\typescript.js:317:30)
    at checkSourceFileWorker (C:\Cursos\Angular\ang-hello-world\node_modules\typescript\lib\typescript.js:65123:20)
    at checkSourceFile (C:\Cursos\Angular\ang-hello-world\node_modules\typescript\lib\typescript.js:65091:13)
    at getDiagnosticsWorker (C:\Cursos\Angular\ang-hello-world\node_modules\typescript\lib\typescript.js:65179:17)
    at Object.getDiagnostics (C:\Cursos\Angular\ang-hello-world\node_modules\typescript\lib\typescript.js:65165:24)
    at C:\Cursos\Angular\ang-hello-world\node_modules\typescript\lib\typescript.js:98703:85
    at runWithCancellationToken (C:\Cursos\Angular\ang-hello-world\node_modules\typescript\lib\typescript.js:98665:24)
    at getBindAndCheckDiagnosticsForFileNoCache (C:\Cursos\Angular\ang-hello-world\node_modules\typescript\lib\typescript.js:98691:20)
    at getAndCacheDiagnostics (C:\Cursos\Angular\ang-hello-world\node_modules\typescript\lib\typescript.js:98956:26)
    at getBindAndCheckDiagnosticsForFile (C:\Cursos\Angular\ang-hello-world\node_modules\typescript\lib\typescript.js:98688:20)

** **Angular Live Development Server is listening on localhost:4200, open your browser on http://localhost:4200/** **

运行这个项目后，我在浏览器上得到的结果是：

Cannot GET /

Answer 1

编辑

如果您使用 angular 9.1.6 现在应该没问题

npm update @angular/cli @angular/core

原帖

Angular 9.1.5 中的某些内容被破坏了 - 如果您运行以下命令，它应该可以工作：

npm install @angular/core@9.1.4 @angular/animations@9.1.4 @angular/common@9.1.4 @angular/forms@9.1.4 @angular/platform-browser@9.1.4 @angular/router@9.1.4 @angular/platform-browser-dynamic@9.1.4 @angular/compiler@9.1.4 @angular/compiler-cli@9.1.4 @angular/language-service@9.1.4

ng build

只花了大约 4-5 个小时试图自己修复它......

该问题似乎源于将 Angular CLI 9.1.4 与 Angular 9.1.5 一起使用（很可能是编译器

当你这样做时，你会看到这个问题

ng --version

如果你得到：

Angular CLI: 9.1.4
Node: 12.16.3
OS: win32 x64

Angular: 9.1.5
... animations, cli, common, compiler, compiler-cli, core, forms
... language-service, platform-browser, platform-browser-dynamic
... router
Ivy Workspace: Yes

然后你需要按照我上面列出的 npm 安装