Property 'observable' does not exist on type 'SymbolConstructor'

[PopGoesTheWza]

Since I found a solution to my problem, this issue is rather informational.

On a small mono-repo (lerna@3.20.2) project:

• node.js v12.16.1 and npm 6.14.2
• typescript@^3.8.3 as root devDependencies
• @types/node@^12.12.29 as root devDependencies
• @sindre/sorhus@^2.1.0 as package dependencies

❯ tsc --build tsconfig.json
node_modules/@sindresorhus/is/dist/index.d.ts:135:13 - error TS2339: Property 'observable' does not exist on type 'SymbolConstructor'.

135     [Symbol.observable](): ObservableLike;
                ~~~~~~~~~~

From what I could gather, observable on type SymbolConstructor is defined in @types/node@12.12.29 (which is installed in the root node_modules), but not in @types/node@13.7.7 (which ends up being installed in the package's node_module as a side effect.)

One kludgy quick-fix could be to add @types/node@^12.12.29 in the package's devDependencies

Another, arguably cleaner solution is to use lerna bootstrap --hoist so that root node_modules prevails.

[Richienb]

type-fest fixed this exact issue in sindresorhus/type-fest#21. Therefore, we just need to fix #85.