Unclear how to type check in a v6 project

[brentd]

Versions

Angular CLI: 6.0.0
Node: 9.11.1
OS: darwin x64
Angular: 6.0.0
... animations, cli, common, compiler, compiler-cli, core, forms
... http, language-service, platform-browser
... platform-browser-dynamic, router

Package                           Version
-----------------------------------------------------------
@angular-devkit/architect         0.6.0
@angular-devkit/build-angular     0.6.0
@angular-devkit/build-optimizer   0.6.0
@angular-devkit/core              0.6.0
@angular-devkit/schematics        0.6.0
@ngtools/webpack                  6.0.0
@schematics/angular               0.6.0
@schematics/update                0.6.0
rxjs                              6.1.0
typescript                        2.7.2
webpack                           4.6.0

Repro steps

• Step 1

ng new myproject using the latest angular-cli

• Step 2

Make a type error in app.component.ts like

export class AppComponent {
  title: NotAType = 'app';
}

Observed behavior

The type error appears in an IDE with Typescript support.

• ng lint does not show the type error
• ng lint --type-check as mentioned in other issues I found results in an error: Architect commands with multiple targets cannot specify overrides. [...]
• ng lint myproject --type-check to appease the Architect error still does not show the type error
• tslint --type-check --project . shows the type error but mentions a deprecation warning. More info.
• tsc --noEmit shows the type error

Desired behavior

I expected ng lint to show type errors. As a new user to Angular it seems to be the one and only interface from the command line intended to answer "is there anything syntactically wrong with my project?". Not including type errors was surprising, and with no clear way to show type errors, led to frustration.

Mention any other details that might be useful (optional)

The Architect error wasn't particularly helpful when I ran ng lint --type-check. For one, I didn't know what Architect was, and the error could have offered an alternative command, e.g. ng lint myproject [args].

[clydin]

Type errors are build time errors not linting errors. The application will not build successfully if any are present. This is one of the advantages of TypeScript; types are first class members of the language.

[brentd]

Type errors are build time errors not linting errors.

I don't disagree. The point of this issue was that it's unclear how Angular users are supposed to type check their apps from the command line (for example, as a precommit hook, on CI, etc).

I'm assuming the answer is tsc --noEmit and no longer ng lint --type-check as I've seen advocated.

[clydin]

Neither. If the goal is to catch build errors then ng build would be appropriate. A type error is no different than any other build error (i.e., fatal). lint errors are stylistic in nature and are not a reflection of the executable viability of the program.

[brentd]

ng build would cover application code but not specs, so of course ng test would also be needed to verify the tests are valid.

I completely understand where you're coming from, I just personally feel that there's utility in being able to verify all project code is free of TS problems in one command, just as it's useful to lint the whole project together. So I'll be adding tsc --noEmit as an npm script.

Thanks for your time @clydin.

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