Angular 9 Upgrade updates to tsconfig.app.json are undocumented.

📚 Docs or angular.io bug report

Description

The Angular 9 upgrade updated the tsconfig.app.json and tsconfig-es5.app.json as follows (the project uses the differential loading workaround from the angular 8 upgrade to allow ng serve to support IE):

tsconfig.app.json
Old:
{
  "extends": "../tsconfig.json",
  "compilerOptions": {
    "outDir": "../out-tsc/app",
    "types": []
  },
  "exclude": [
    "src/test.ts",
    "**/*.spec.ts"
  ]
}
New:
{
  "extends": "../tsconfig.json",
  "compilerOptions": {
    "outDir": "../out-tsc/app",
    "types": []
  },
  "files": [
    "main.ts",
    "polyfills.ts"
  ],
  "include": [
    "src/**/*.d.ts"
  ]
}

(i.e.) ‘exclude’ was removed and ‘files’ and ‘include’ were added.

tsconfig-es5.app.json
Old:
{
    "extends": "./tsconfig.app.json",
    "compilerOptions": {
        "target": "es5"
     }
}
New:
{
    "extends": "./tsconfig.app.json",
    "compilerOptions": {
        "target": "es5"
     }
   ,  "include": [
    "src/**/*.d.ts"
  ]
}

Checking the tsconfig.app.json for a default CLI Angular 8 project upgraded to 9 the file is:

{
  "extends": "./tsconfig.json",
  "compilerOptions": {
    "outDir": "./out-tsc/app",
    "types": []
  },
  "files": [
    "src/main.ts",
    "src/polyfills.ts"
  ],
  "include": [
    "src/**/*.ts"
  ],
  "exclude": [
    "src/test.ts",
    "src/**/*.spec.ts"
  ]
}

This seems to be the only information about this in the upgrade documentation: We have updated the tsconfig.app.json to limit the files compiled. If you rely on other files being included in the compilation, such as a typings.d.ts file, you need to manually add it to the compilation.

I think the addition of the include statement may be related to: https://github.com/angular/angular-cli/issues/16923.

And the addition of files may be related to: https://github.com/angular/angular-cli/issues/17066

Why were these changes made? Why was the ‘exclude’ statement removed? Why are the changes different for the es5 file?

Please update the upgrade documentation to include information about why these the upgrader is makes these changes.

What’s the affected URL?**

https://update.angular.io/#8.0:9.0l3 https://angular.io/guide/updating-to-version-9

[tdkehoe]

What does the “d” mean in “src/**/*.d.ts”? It includes files that don’t have a “d” and excludes other files. And what’s the difference between “files” and “include”? Which files or paths go where?

[roopeshreddy]

I referred this question on Enterprise slack group and @mgechev confirmed me my assumption was correct! As @devin5885 explained, we may need to explicitly include the additional files to be compiled.

IMO this change is for simplification, but unfortunately, it’s not documented anywhere!

I just shared this information, so that, if anyone is looking for this, it may be helpful!