no-rootdir-includes-outdir

Disallow rootDir values that overlap with or include the outDir, which causes TypeScript to read and then immediately overwrite the same files.

Targeted pattern scope

The compilerOptions.rootDir and compilerOptions.outDir fields in any tsconfig*.json file.

What this rule reports

This rule reports when rootDir and outDir are the same path, or when rootDir is a parent of outDir such that generated output would be written into the source tree.

Why this rule exists

When outDir is nested inside rootDir, TypeScript's next compilation pass will include the previously-generated JavaScript and declaration files as inputs. This creates a feedback loop: the output of one build becomes an input for the next, causing growing compile times, duplicate declarations, and incorrect type information.

The correct pattern is to use sibling directories: src/ as rootDir and a separate top-level dist/ or build/ directory as outDir, so that output is always distinct from source.

❌ Incorrect

{
    "compilerOptions": {
        "rootDir": ".",
        "outDir": "./dist"
    }
}

dist/ is a subdirectory of . (rootDir), so generated files fall inside the source tree.

{
    "compilerOptions": {
        "rootDir": "./src",
        "outDir": "./src/dist"
    }
}

outDir is directly nested inside rootDir.

✅ Correct

{
    "compilerOptions": {
        "rootDir": "./src",
        "outDir": "./dist"
    }
}

src/ and dist/ are siblings; output is written entirely outside the source root.

When not to use it

Disable this rule only when a custom build pipeline explicitly excludes the output directory from subsequent TypeScript compilations via exclude.

Package documentation

Rule catalog ID: R012

Targeted pattern scope​

What this rule reports​

Why this rule exists​

❌ Incorrect​

✅ Correct​

When not to use it​

Package documentation​

Further reading​