require-force-consistent-casing-in-file-names

Require "forceConsistentCasingInFileNames": true in compilerOptions to prevent import-path casing mismatches that silently break on case-sensitive file systems.

Targeted pattern scope

The compilerOptions.forceConsistentCasingInFileNames field in any tsconfig*.json file.

What this rule reports

This rule reports when compilerOptions.forceConsistentCasingInFileNames is absent or explicitly set to false.

Why this rule exists

Windows and macOS use case-insensitive file systems by default. Linux uses a case-sensitive file system. This difference is a frequent source of bugs that are invisible in local development but break in CI or production.

Consider this scenario:

project/
  src/
    Utils.ts       ← file is named with capital U
    index.ts       ← imports with lowercase u

// index.ts — works on Windows/macOS, fails on Linux
import { helper } from "./utils"; // case mismatch: Utils vs utils

On Windows and macOS the import resolves successfully because the file system ignores casing. On Linux the import fails with Cannot find module './utils', producing a build or runtime error only in CI or deployment.

forceConsistentCasingInFileNames: true makes TypeScript report an error when an import path uses different casing than the actual file name — even on case-insensitive systems — catching the mismatch before it reaches a case-sensitive environment.

The auto-fixer adds "forceConsistentCasingInFileNames": true to compilerOptions.

❌ Incorrect

{
    "compilerOptions": {
        "target": "ES2022",
        "module": "NodeNext"
    }
}

forceConsistentCasingInFileNames is absent; casing mismatches will not be reported and may silently break on Linux CI.

{
    "compilerOptions": {
        "forceConsistentCasingInFileNames": false
    }
}

Explicitly disabled — cross-platform import casing errors are suppressed.

✅ Correct

{
    "compilerOptions": {
        "target": "ES2022",
        "module": "NodeNext",
        "forceConsistentCasingInFileNames": true
    }
}

Casing mismatches in import paths are reported.

When not to use it

Disable this rule only in projects that are guaranteed to run exclusively on case-insensitive file systems and have no CI pipeline or deployment environment running on Linux. This scenario is rare and shrinking as cloud-native development becomes the norm.

Package documentation

Rule catalog ID: R028

Targeted pattern scope​

What this rule reports​

Why this rule exists​

❌ Incorrect​

✅ Correct​

When not to use it​

Package documentation​

Further reading​