``It seems that TypeScript is not adhering to standard logic

Question

``It seems that TypeScript is not adhering to standard logic

const PACT_TAGS: string[] = [];

const CI_BRANCH: string | undefined = process.env.CI_BRANCH;
const CI_USER: string | undefined = process.env.CI_USER;
const CI_COMMIT: string | undefined = process.env.CI_COMMIT;

const isCiPipeline = CI_BRANCH !== undefined && CI_USER !== undefined && CI_COMMIT !== undefined;

if (isCiPipeline) {
    PACT_TAGS.push(CI_COMMIT); // <- error
    PACT_TAGS.push(CI_BRANCH); // <- error
    PACT_TAGS.push(CI_USER); // <- error
}

An issue has been encountered:

const CI_COMMIT: string | undefined
Argument of type 'string | undefined' is not assignable to parameter of type 'string'.
  Type 'undefined' is not assignable to type 'string'.ts(2345)

The intention here is clear. The lines within the if clause are only meant to be executed if the specified variables are strings. While I could explicitly cast them as <string>, doing so would defeat the purpose of using TypeScript.

typescript

Answer 1

Answer №1

Following the suggestion of @jonrsharpe, it's important to note that isCiPipeline is a boolean value and doesn't assist in narrowing down the types of your constants so that TypeScript only recognizes them as string, rather than string | undefined.

One recommendation is to eliminate the undefined checks by incorporating them directly into the code:

if (CI_BRANCH !== undefined && CI_USER !== undefined && CI_COMMIT !== undefined) {
  PACT_TAGS.push(CI_COMMIT);
  PACT_TAGS.push(CI_BRANCH);
  PACT_TAGS.push(CI_USER);
}

By doing this, TypeScript can deduce from the if statement that none of the constants could be of type undefined, confirming them as strictly string.

Alternatively, if you're certain about your implementation, you have the option to explicitly declare to TypeScript that the constants are not undefined using the non-null assertion operator:

if (isCiPipeline) {
  PACT_TAGS.push(CI_COMMIT!);
  PACT_TAGS.push(CI_BRANCH!);
  PACT_TAGS.push(CI_USER!);
}

Answer 2

Following the suggestion of @jonrsharpe, it's important to note that isCiPipeline is a boolean value and doesn't assist in narrowing down the types of your constants so that TypeScript only recognizes them as string, rather than string | undefined.

One recommendation is to eliminate the undefined checks by incorporating them directly into the code:

if (CI_BRANCH !== undefined && CI_USER !== undefined && CI_COMMIT !== undefined) {
  PACT_TAGS.push(CI_COMMIT);
  PACT_TAGS.push(CI_BRANCH);
  PACT_TAGS.push(CI_USER);
}

By doing this, TypeScript can deduce from the if statement that none of the constants could be of type undefined, confirming them as strictly string.

Alternatively, if you're certain about your implementation, you have the option to explicitly declare to TypeScript that the constants are not undefined using the non-null assertion operator:

if (isCiPipeline) {
  PACT_TAGS.push(CI_COMMIT!);
  PACT_TAGS.push(CI_BRANCH!);
  PACT_TAGS.push(CI_USER!);
}

``It seems that TypeScript is not adhering to standard logic

Answer №1

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