Repository: eslint/eslint
File: lib/eslint/flat-eslint.js (JavaScript)

Code before:
            throw new Error("'code' must be a string");
        }

        if (typeof options !== "object") {
            throw new Error("'options' must be an object, null, or undefined");
        }

        // Options validation

        const {
            filePath,
            warnIgnored,
            ...unknownOptions
        } = options || {};

        const unknownOptionKeys = Object.keys(unknownOptions);

        if (unknownOptionKeys.length > 0) {
            throw new Error(`'options' must not include the unknown option(s): ${unknownOptionKeys.join(", ")}`);
        }

        if (filePath !== void 0 && !isNonEmptyString(filePath)) {
            throw new Error("'options.filePath' must be a non-empty string or undefined");
        }

        if (!(typeof warnIgnored === "boolean" || typeof warnIgnored === "undefined")) {
            throw new Error("'options.warnIgnored' must be a boolean or undefined");
        }

        // Now we can get down to linting

        const {
            linter,
            options: eslintOptions
        } = privateMembers.get(this);
        const configs = await calculateConfigArray(this, eslintOptions);
        const {
            allowInlineConfig,
            cwd,
            fix,
            reportUnusedDisableDirectives,
            warnIgnored: constructorWarnIgnored
        } = eslintOptions;
        const results = [];
        const startTime = Date.now();
        const resolvedFilename = path.resolve(cwd, filePath || "__placeholder__.js");

        // Clear the last used config arrays.
        if (resolvedFilename && await this.isPathIgnored(resolvedFilename)) {
            const shouldWarnIgnored = typeof warnIgnored === "boolean" ? warnIgnored : constructorWarnIgnored;


Review comment (suggestion):
This might be a bit easier to understand.

```suggestion
        if (typeof warnIgnored !== "boolean" && typeof warnIgnored !== "undefined")) {
```

Code after:
            throw new Error("'code' must be a string");
        }

        if (typeof options !== "object") {
            throw new Error("'options' must be an object, null, or undefined");
        }

        // Options validation

        const {
            filePath,
            warnIgnored,
            ...unknownOptions
        } = options || {};

        const unknownOptionKeys = Object.keys(unknownOptions);

        if (unknownOptionKeys.length > 0) {
            throw new Error(`'options' must not include the unknown option(s): ${unknownOptionKeys.join(", ")}`);
        }

        if (filePath !== void 0 && !isNonEmptyString(filePath)) {
            throw new Error("'options.filePath' must be a non-empty string or undefined");
        }

        if (typeof warnIgnored !== "boolean" && typeof warnIgnored !== "undefined") {
            throw new Error("'options.warnIgnored' must be a boolean or undefined");
        }

        // Now we can get down to linting

        const {
            linter,
            options: eslintOptions
        } = privateMembers.get(this);
        const configs = await calculateConfigArray(this, eslintOptions);
        const {
            allowInlineConfig,
            cwd,
            fix,
            reportUnusedDisableDirectives,
            warnIgnored: constructorWarnIgnored
        } = eslintOptions;
        const results = [];
        const startTime = Date.now();
        const resolvedFilename = path.resolve(cwd, filePath || "__placeholder__.js");

        // Clear the last used config arrays.
        if (resolvedFilename && await this.isPathIgnored(resolvedFilename)) {
            const shouldWarnIgnored = typeof warnIgnored === "boolean" ? warnIgnored : constructorWarnIgnored;