no-empty-theme-classic-custom-css

Disallow empty customCss entries in Docusaurus classic theme config.

Targeted pattern scope

This rule focuses on docusaurus.config.* files.

It checks Docusaurus classic theme customCss configuration through:

classic preset theme.customCss
direct @docusaurus/theme-classic options

What this rule reports

This rule reports empty customCss strings and empty string entries inside customCss arrays.

Why this rule exists

customCss entries are file paths. Empty strings do not point to meaningful stylesheets and only make the config harder to read and review.

Removing empty entries keeps the classic theme config honest and easier to maintain.

❌ Incorrect

export default {
    presets: [[
        "@docusaurus/preset-classic",
        {
            theme: { customCss: "" },
        },
    ]],
};

✅ Correct

export default {
    presets: [[
        "@docusaurus/preset-classic",
        {
            theme: { customCss: "./src/css/custom.css" },
        },
    ]],
};

Behavior and migration notes

This rule autofixes the simple literal cases it can safely prove:

remove empty entries from customCss arrays
remove a customCss property when its value is an empty string

Additional examples

❌ Incorrect — empty array entry

export default {
    presets: [[
        "@docusaurus/preset-classic",
        {
            theme: {
                customCss: ["./src/css/custom.css", "", "./src/css/extra.css"],
            },
        },
    ]],
};

✅ Correct — only real stylesheet entries remain

export default {
    presets: [[
        "@docusaurus/preset-classic",
        {
            theme: {
                customCss: ["./src/css/custom.css", "./src/css/extra.css"],
            },
        },
    ]],
};

ESLint flat config example

import docusaurus2 from "eslint-plugin-docusaurus-2";

export default [docusaurus2.configs.recommended];

When not to use it

Do not use this rule if your project intentionally keeps empty placeholder stylesheet entries during a staged migration and you do not want linting to remove them yet.

Rule catalog ID: R096

Targeted pattern scope​

What this rule reports​

Why this rule exists​

❌ Incorrect​

✅ Correct​

Behavior and migration notes​

Additional examples​

❌ Incorrect — empty array entry​

✅ Correct — only real stylesheet entries remain​

ESLint flat config example​

When not to use it​

Further reading​