Unable to compile with typescript 2.4.2 and "strictNullChecks": true,

Hello,

I’m using popper.js with typescript (being imported from @blueprintjs/labs node module) and when I have "strictNullChecks": true, I get the error below. If I change my setting to "strictNullChecks": false, then everything compiles. Let me know if I should report this to blueprintjs but figured I would start here for now. @giladgray might know what’s up. I did a full rm -rf node_modules and yarn install before seeing this error.

yarn build v0.27.5
$ react-scripts-ts build
Creating an optimized production build...
ts-loader: Using typescript@2.4.2 and /Users/dennison/projects/echelon/echelon-web/tsconfig.json
Failed to compile.

/Users/dennison/projects/echelon/echelon-web/node_modules/popper.js/index.d.ts
(38,5): error TS2411: Property 'shift' of type 'BaseModifier | undefined' is not assignable to string index type 'BaseModifier & Record<string, any>'.

/Users/dennison/projects/echelon/echelon-web/node_modules/popper.js/index.d.ts
(39,5): error TS2411: Property 'offset' of type '(BaseModifier & { offset?: string | number | undefined; }) | undefined' is not assignable to string index type 'BaseModifier & Record<string, any>'.

/Users/dennison/projects/echelon/echelon-web/node_modules/popper.js/index.d.ts
(42,5): error TS2411: Property 'preventOverflow' of type '(BaseModifier & { priority?: ("bottom" | "top" | "left" | "right")[] | undefined; padding?: numbe...' is not assignable to string index type 'BaseModifier & Record<string, any>'.

/Users/dennison/projects/echelon/echelon-web/node_modules/popper.js/index.d.ts
(47,5): error TS2411: Property 'keepTogether' of type 'BaseModifier | undefined' is not assignable to string index type 'BaseModifier & Record<string, any>'.

/Users/dennison/projects/echelon/echelon-web/node_modules/popper.js/index.d.ts
(48,5): error TS2411: Property 'arrow' of type '(BaseModifier & { element?: string | Element | undefined; }) | undefined' is not assignable to string index type 'BaseModifier & Record<string, any>'.

/Users/dennison/projects/echelon/echelon-web/node_modules/popper.js/index.d.ts
(51,5): error TS2411: Property 'flip' of type '(BaseModifier & { behavior?: ("bottom" | "top" | "left" | "right")[] | "flip" | "clockwise" | "co...' is not assignable to string index type 'BaseModifier & Record<string, any>'.

/Users/dennison/projects/echelon/echelon-web/node_modules/popper.js/index.d.ts
(56,5): error TS2411: Property 'inner' of type 'BaseModifier | undefined' is not assignable to string index type 'BaseModifier & Record<string, any>'.

/Users/dennison/projects/echelon/echelon-web/node_modules/popper.js/index.d.ts
(57,5): error TS2411: Property 'hide' of type 'BaseModifier | undefined' is not assignable to string index type 'BaseModifier & Record<string, any>'.

/Users/dennison/projects/echelon/echelon-web/node_modules/popper.js/index.d.ts
(58,5): error TS2411: Property 'applyStyle' of type '(BaseModifier & { onLoad?: Function | undefined; gpuAcceleration?: boolean | undefined; }) | unde...' is not assignable to string index type 'BaseModifier & Record<string, any>'.

[DrewDennison]

Thanks @MrFrankel "skipLibCheck": true, did the trick. TIL

[MrFrankel]

@FezVrasta, no, it will simply not check them for internal errors, obviously libraries that support types should not have errors in them, but as consumers we cant have our build’s fail due to a TS error