Namespaces and variables type checking | TypeScript Community | Page 1

sick warren May 28, 2023, 7:59 AM

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Hello, I am using a code-generation library and had trouble wrapping my mind around some issue. Take a look at the following piece of code:

export namespace components {
  export const component2 = {
    component1Flag: components['component1'].flag
  }
  export const component1 = {
    flag: true
  }
}

On a strict type level, this works. Typescript sees no type issue in the previous code. However, at runtime this piece of code fails with the error components['component1'] is undefined on line 3.

Why is this code authorized at the type level while it doesn't run?

Thank you

royal kiln May 28, 2023, 11:29 AM

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@sick warren because a module simply declares different objects

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and the order those objects are declared in is kinda lost in the process

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but the order matters at runtime ofc

royal kiln May 28, 2023, 11:30 AM

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royal kiln and the order those objects are declared in is kinda lost in the process

the same way whan you'd declare a module and export a bunch of objects

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the order the objects are created doesn't for the consumers of the module, only within the module itself

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it's the same reason recursive import loops also exist

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declaring objects is one thing

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instantiating them and giving them a value in the right order is another

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tldr. refering to the current module and accessing objects from it is a bad idea

#Namespaces and variables type checking