eslint/lib/rules/no-inline-comments.js

/**
 * @fileoverview Enforces or disallows inline comments.
 * @author Greg Cochard
 */
"use strict";

const astUtils = require("./utils/ast-utils");

//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------

module.exports = {
    meta: {
        type: "suggestion",

        docs: {
            description: "disallow inline comments after code",
            category: "Stylistic Issues",
            recommended: false,
            url: "https://eslint.org/docs/rules/no-inline-comments"
        },

        schema: [
            {
                type: "object",
                properties: {
                    ignorePattern: {
                        type: "string"
                    }
                },
                additionalProperties: false
            }
        ],

        messages: {
            unexpectedInlineComment: "Unexpected comment inline with code."
        }
    },

    create(context) {
        const sourceCode = context.getSourceCode();
        const options = context.options[0];
        let customIgnoreRegExp;

        if (options && options.ignorePattern) {
            customIgnoreRegExp = new RegExp(options.ignorePattern, "u");
        }

        /**
         * Will check that comments are not on lines starting with or ending with code
         * @param {ASTNode} node The comment node to check
         * @private
         * @returns {void}
         */
        function testCodeAroundComment(node) {

            const startLine = String(sourceCode.lines[node.loc.start.line - 1]),
                endLine = String(sourceCode.lines[node.loc.end.line - 1]),
                preamble = startLine.slice(0, node.loc.start.column).trim(),
                postamble = endLine.slice(node.loc.end.column).trim(),
                isPreambleEmpty = !preamble,
                isPostambleEmpty = !postamble;

            // Nothing on both sides
            if (isPreambleEmpty && isPostambleEmpty) {
                return;
            }

            // Matches the ignore pattern
            if (customIgnoreRegExp && customIgnoreRegExp.test(node.value)) {
                return;
            }

            // JSX Exception
            if (
                (isPreambleEmpty || preamble === "{") &&
                (isPostambleEmpty || postamble === "}")
            ) {
                const enclosingNode = sourceCode.getNodeByRangeIndex(node.range[0]);

                if (enclosingNode && enclosingNode.type === "JSXEmptyExpression") {
                    return;
                }
            }

            // Don't report ESLint directive comments
            if (astUtils.isDirectiveComment(node)) {
                return;
            }

            context.report({
                node,
                messageId: "unexpectedInlineComment"
            });
        }

        //--------------------------------------------------------------------------
        // Public
        //--------------------------------------------------------------------------

        return {
            Program() {
                sourceCode.getAllComments()
                    .filter(token => token.type !== "Shebang")
                    .forEach(testCodeAroundComment);
            }
        };
    }
};