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no-disable-strict-subset

Disallow explicitly setting individual strict-mode flags to false when strict: true is already enabled in compilerOptions.

Targeted pattern scopeโ€‹

The compilerOptions.strict field and the individual strict-mode sub-flags (strictNullChecks, strictFunctionTypes, strictBindCallApply, strictBuiltinIteratorReturn, strictPropertyInitialization, noImplicitAny, noImplicitThis, alwaysStrict, useUnknownInCatchVariables) in any tsconfig*.json file.

What this rule reportsโ€‹

This rule reports when "strict": true is present alongside any individual strict-mode sub-flag explicitly set to false. The combination is misleading: the intent of strict: true is to enable all current and future strict checks, but the explicit false overrides silently erode that guarantee.

Why this rule existsโ€‹

strict: true is a composite flag that bundles all strict checks into one declaration. When individual sub-flags are turned off the configuration becomes a maintenance hazard: a reader must mentally subtract each disabled flag from the composite, and new strict sub-flags added by TypeScript in future versions may be inadvertently disabled too.

If a specific check is legitimately too strict for a codebase, the correct approach is to disable the entire strict flag and explicitly list only the individual checks that should be active, making the intended strictness level unambiguous.

โŒ Incorrectโ€‹

{
    "compilerOptions": {
        "strict": true,
        "strictNullChecks": false
    }
}

The strict: true intention is undermined by the strictNullChecks: false override.

โœ… Correctโ€‹

Enable everything via strict:

{
    "compilerOptions": {
        "strict": true
    }
}

Or, if strictNullChecks is genuinely unsuitable, disable strict and enumerate exactly what should be enabled:

{
    "compilerOptions": {
        "noImplicitAny": true,
        "strictFunctionTypes": true,
        "strictBindCallApply": true
    }
}

When not to use itโ€‹

Disable this rule during a gradual strictness migration where strict: true has been added as a future target but some checks must temporarily remain disabled to unblock a release.

Package documentationโ€‹

Rule catalog ID: R005

Further readingโ€‹