TSLint has detected an error: the name 'Observable' has been shadowed

Question

TSLint has detected an error: the name 'Observable' has been shadowed

When I run tslint, I am encountering an error that was not present before. It reads as follows:

ERROR: C:/...path..to../observable-debug-operator.ts[27, 13]: Shadowed name: 'Observable'

I recently implemented a debug operator to my Observable by following this tutorial. The debug operator is functioning correctly, but I keep receiving this lint error. Oddly enough, I have been using the debug operator for some time without experiencing any lint errors, so I'm unsure why it's happening now.

The issue seems to be with the code on line 27 where I extended the type definition with the debug method:

declare module 'rxjs/Observable' {
  interface Observable<T> { // line 27
    debug: (...any) => Observable<T>;
  }
}

If anyone has insights on how I can resolve this lint error, I would greatly appreciate it. Thank you!

angular typescript rxjs observable tslint

Answer 1

Answer №1

Here's a simple illustration of variable shadowing to highlight the concept.

var x = 4;

function example() {
    var x = 5; // The inner scope is shadowing the outer scope's x variable
}

If you're adding to an interface (e.g. both instances of Observable share a common root), it's not technically shadowing. However, having multiple levels of Observable can lead to ambiguity in reference.

You can disable shadowing warnings with this setting:

"no-shadowed-variable": [
  true,
  {
    "class": true,
    "enum": true,
    "function": true,
    "interface": false,
    "namespace": true,
    "typeAlias": false,
    "typeParameter": false
  }
]

Is interface shadowing problematic in TypeScript?

Generally, no - since declaring an interface within a function would already raise compiler errors if there were issues. Additionally, interfaces are removed during compilation, ensuring clarity even when used in JavaScript environments.

I'm open to revising my stance if presented with a practical scenario where interface shadowing could potentially pose problems.

Answer 2

Here's a simple illustration of variable shadowing to highlight the concept.

var x = 4;

function example() {
    var x = 5; // The inner scope is shadowing the outer scope's x variable
}

If you're adding to an interface (e.g. both instances of Observable share a common root), it's not technically shadowing. However, having multiple levels of Observable can lead to ambiguity in reference.

You can disable shadowing warnings with this setting:

"no-shadowed-variable": [
  true,
  {
    "class": true,
    "enum": true,
    "function": true,
    "interface": false,
    "namespace": true,
    "typeAlias": false,
    "typeParameter": false
  }
]

Is interface shadowing problematic in TypeScript?

Generally, no - since declaring an interface within a function would already raise compiler errors if there were issues. Additionally, interfaces are removed during compilation, ensuring clarity even when used in JavaScript environments.

I'm open to revising my stance if presented with a practical scenario where interface shadowing could potentially pose problems.

Answer 3

Answer №2

Essentially, the concept of shadowing in programming is well illustrated by Fenton. Shadowing occurs when there are naming collisions.

Instead of using 'x' as the name for nested variables/parameters, why not choose a different name? ;)

Here's an example to demonstrate this:

...
.retryWhen(error => {
  return error
    .mergeMap((error: any) => {
      if (error.status === 500) {
...

In this code snippet, you can see multiple instances of the variable being named 'error'.

Answer 4

Essentially, the concept of shadowing in programming is well illustrated by Fenton. Shadowing occurs when there are naming collisions.

Instead of using 'x' as the name for nested variables/parameters, why not choose a different name? ;)

Here's an example to demonstrate this:

...
.retryWhen(error => {
  return error
    .mergeMap((error: any) => {
      if (error.status === 500) {
...

In this code snippet, you can see multiple instances of the variable being named 'error'.

Answer 5

Answer №3

After re-installing all my package dependencies, including tslint, the error I was experiencing seems to be fixed. Thank you for your assistance and support in resolving this issue :)

Answer 6

After re-installing all my package dependencies, including tslint, the error I was experiencing seems to be fixed. Thank you for your assistance and support in resolving this issue :)

TSLint has detected an error: the name 'Observable' has been shadowed

Answer №1

Answer №2

Answer №3

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