Request : Progressive support for strictNullCheck

[olamothe]

Feature Request/Suggestion

As an existing user of TypeScript, I would like to be able to gradually enable the new compiler options for strict null check in my project. As of now, the only way to do this that I'm aware of is to set the global flag strictNullCheck to true for the compiler, for the whole project.

For an already existing project with a big codebase, this becomes a monumental task to fix every single file before being able to use this feature going forward.

TypeScript Version : Currently using 2.0.3

Expected behaviour

Add support for special annotation in .ts files, a bit like Facebook's Flow annotation system.

For example, if the first line in a file contains an annotation like this :

/* @strictNullCheck */

This would tell the compiler to activate this option for this file only.

This could very well be expanded for other compiler options.

This would allow a big codebase to gradually migrate less painfully.

[RyanCavanaugh]

As outlined here #9432 (comment) , there isn't a well-defined way to determine what would or wouldn't be an error under this flag. We'd need some way of guessing at whether or not to issue an error in a particular place.

[RyanCavanaugh]

Declined in #8405