Strict Angular

If you like to have your TypeScript type checking to be stricter, there are a few settings that can be turned on within your ts.config.

TypeScript Compiler Options

When generating a new project from the Angular CLI with the --strict flag, the following compiler options are added to tsconfig.json for you.

// tsconfig.json
{
    "noImplicitAny": true,
    "noImplicitReturns": true,
    "noImplicitThis": true,
    "noFallthroughCasesInSwitch": true,
    "strictNullChecks": true,
}

These settings do not encompass all of TypeScripts strict flag as detailed in the TypeScript compiler docs, just a subset.

// tsconfig.json
{
    "noImplicitReturns": true,
    "noFallthroughCasesInSwitch": true,
}

Are options that TypeScript would not turn on with its strict flag.

If you would like to make your Angular project fully strict, replace the provided options like so:

// tsconfig.json
{
    "strict": true,
    "noImplicitReturns": true,
    "noFallthroughCasesInSwitch": true,
}

Angular Compiler Options

Angular compiler options are added within tsconfig.json. For projects built with the Angular CLI fullTemplateTypeCheck will be defaulted on.

{
    "angularCompilerOptions": {
        "fullTemplateTypeCheck": true,
    }
}

Although defaulted off, it is recommended within the Angular documentation that strictInjectionParameters is turned on.

{
    "angularCompilerOptions": {
        "strictInjectionParameters": true,
    }
}

As of Angular 9, with Ivy turned on we can also turn on Strict mode for template checking.

{
    "angularCompilerOptions": {
        "strictTemplates": true
    }
}

This is a superset of fullTemplateTypeCheck so when strictTemplates is turn on you can remove the config for fullTemplateTypeCheck, ending up with something like this:

{
    "angularCompilerOptions": {
        "strictInjectionParameters": true,
        "strictTemplates": true
    }
}