eslint-plugin-mdx/lib/processors/markdown.js

ESLint Plugin for MDX

/**
 * based of @link https://github.com/eslint/eslint-plugin-markdown/blob/main/lib/processor.js
 *
 * @fileoverview Processes Markdown files for consumption by ESLint.
 * @author Brandon Mills
 */
import { last } from 'eslint-mdx';
import { remarkProcessor } from '../rules';
const UNSATISFIABLE_RULES = new Set([
    'eol-last',
    'unicode-bom', // Code blocks will begin in the middle of Markdown files
]);
const SUPPORTS_AUTOFIX = true;
const blocksCache = {};
/**
 * Performs a depth-first traversal of the Markdown AST.
 * @param node A Markdown AST node.
 * @param callbacks A map of node types to callbacks.
 * @param parent The node's parent AST node.
 */
function traverse(node, callbacks, parent) {
    if (callbacks[node.type]) {
        callbacks[node.type](node, parent);
    }
    if (typeof node.children !== 'undefined') {
        const parent = node;
        for (const child of parent.children) {
            traverse(child, callbacks, parent);
        }
    }
}
/**
 * Converts leading HTML comments to JS block comments.
 * @param html The text content of an HTML AST node.
 * @returns JS block comment.
 */
function getComment(html) {
    const commentStart = '<!--';
    const commentEnd = '-->';
    const regex = /^(eslint\b|global\s)/u;
    if (html.slice(0, commentStart.length) !== commentStart ||
        html.slice(-commentEnd.length) !== commentEnd) {
        return '';
    }
    const comment = html.slice(commentStart.length, -commentEnd.length);
    if (!regex.test(comment.trim())) {
        return '';
    }
    return comment;
}
// Before a code block, blockquote characters (`>`) are also considered
// "whitespace".
const leadingWhitespaceRegex = /^[>\s]*/u;
/**
 * Gets the offset for the first column of the node's first line in the
 * original source text.
 * @param node A Markdown code block AST node.
 * @returns The offset for the first column of the node's first line.
 */
function getBeginningOfLineOffset(node) {
    return node.position.start.offset - node.position.start.column + 1;
}
/**
 * Gets the leading text, typically whitespace with possible blockquote chars,
 * used to indent a code block.
 * @param text The text of the file.
 * @param node A Markdown code block AST node.
 * @returns The text from the start of the first line to the opening
 *     fence of the code block.
 */
function getIndentText(text, node) {
    return leadingWhitespaceRegex.exec(text.slice(getBeginningOfLineOffset(node)))[0];
}
/**
 * When applying fixes, the postprocess step needs to know how to map fix ranges
 * from their location in the linted JS to the original offset in the Markdown.
 * Configuration comments and indentation trimming both complicate this process.
 *
 * Configuration comments appear in the linted JS but not in the Markdown code
 * block. Fixes to configuration comments would cause undefined behavior and
 * should be ignored during postprocessing. Fixes to actual code after
 * configuration comments need to be mapped back to the code block after
 * removing any offset due to configuration comments.
 *
 * Fenced code blocks can be indented by up to three spaces at the opening
 * fence. Inside of a list, for example, this indent can be in addition to the
 * indent already required for list item children. Leading whitespace inside
 * indented code blocks is trimmed up to the level of the opening fence and does
 * not appear in the linted code. Further, lines can have less leading
 * whitespace than the opening fence, so not all lines are guaranteed to have
 * the same column offset as the opening fence.
 *
 * The source code of a non-configuration-comment line in the linted JS is a
 * suffix of the corresponding line in the Markdown code block. There are no
 * differences within the line, so the mapping need only provide the offset
 * delta at the beginning of each line.
 * @param text The text of the file.
 * @param node A Markdown code block AST node.
 * @param comments List of configuration comment strings that will be
 *     inserted at the beginning of the code block.
 * @returns A list of offset-based adjustments, where lookups are
 *     done based on the `js` key, which represents the range in the linted JS,
 *     and the `md` key is the offset delta that, when added to the JS range,
 *     returns the corresponding location in the original Markdown source.
 */
function getBlockRangeMap(text, node, comments) {
    /*
     * The parser sets the fenced code block's start offset to wherever content
     * should normally begin (typically the first column of the line, but more
     * inside a list item, for example). The code block's opening fancy may be
     * further indented by up to three characters. If the code block has
     * additional indenting, the opening fence's first backtick may be up to
     * three whitespace characters after the start offset.
     */
    const startOffset = getBeginningOfLineOffset(node);
    /*
     * Extract the Markdown source to determine the leading whitespace for each
     * line.
     */
    const code = text.slice(startOffset, node.position.end.offset);
    const lines = code.split('\n');
    /*
     * The parser trims leading whitespace from each line of code within the
     * fenced code block up to the opening fence's first backtick. The first
     * backtick's column is the AST node's starting column plus any additional
     * indentation.
     */
    const baseIndent = getIndentText(text, node).length;
    /*
     * Track the length of any inserted configuration comments at the beginning
     * of the linted JS and start the JS offset lookup keys at this index.
     */
    const commentLength = comments.reduce((len, comment) => len + comment.length + 1, 0);
    /*
     * In case there are configuration comments, initialize the map so that the
     * first lookup index is always 0. If there are no configuration comments,
     * the lookup index will also be 0, and the lookup should always go to the
     * last range that matches, skipping this initialization entry.
     */
    const rangeMap = [
        {
            js: 0,
            md: 0,
        },
    ];
    // Start the JS offset after any configuration comments.
    let jsOffset = commentLength;
    /*
     * Start the Markdown offset at the beginning of the block's first line of
     * actual code. The first line of the block is always the opening fence, so
     * the code begins on the second line.
     */
    let mdOffset = startOffset + lines[0].length + 1;
    /*
     * For each line, determine how much leading whitespace was trimmed due to
     * indentation. Increase the JS lookup offset by the length of the line
     * post-trimming and the Markdown offset by the total line length.
     */
    for (let i = 0; i + 1 < lines.length; i++) {
        const line = lines[i + 1];
        const leadingWhitespaceLength = leadingWhitespaceRegex.exec(line)[0].length;
        // The parser trims leading whitespace up to the level of the opening
        // fence, so keep any additional indentation beyond that.
        const trimLength = Math.min(baseIndent, leadingWhitespaceLength);
        rangeMap.push({
            js: jsOffset,
            // Advance `trimLength` character from the beginning of the Markdown
            // line to the beginning of the equivalent JS line, then compute the
            // delta.
            md: mdOffset + trimLength - jsOffset,
        });
        // Accumulate the current line in the offsets, and don't forget the
        // newline.
        mdOffset += line.length + 1;
        jsOffset += line.length - trimLength + 1;
    }
    return rangeMap;
}
const LANGUAGES_MAPPER = {
    javascript: 'js',
    javascriptreact: 'jsx',
    typescript: 'ts',
    typescriptreact: 'tsx',
    markdown: 'md',
    mdown: 'md',
    mkdn: 'md',
};
/**
 * get short language
 * @param lang original language
 * @returns short language
 */
function getShortLang(lang) {
    const language = last(lang.split(/\s/u)[0].split('.')).toLowerCase();
    return LANGUAGES_MAPPER[language] || language;
}
/**
 * Extracts lintable JavaScript code blocks from Markdown text.
 * @param text The text of the file.
 * @param filename The filename of the file
 * @returns Source code strings to lint.
 */
function preprocess(text, filename) {
    const ast = remarkProcessor.parse(text);
    const blocks = [];
    blocksCache[filename] = blocks;
    traverse(ast, {
        code(node, parent) {
            const comments = [];
            if (node.lang) {
                let index = parent.children.indexOf(node) - 1;
                let previousNode = parent.children[index];
                while (previousNode && previousNode.type === 'html') {
                    const comment = getComment(previousNode.value);
                    if (!comment) {
                        break;
                    }
                    if (comment.trim() === 'eslint-skip') {
                        return;
                    }
                    comments.unshift(`/*${comment}*/`);
                    index--;
                    previousNode = parent.children[index];
                }
                blocks.push(Object.assign(Object.assign({}, node), { baseIndentText: getIndentText(text, node), comments, rangeMap: getBlockRangeMap(text, node, comments) }));
            }
        },
    });
    return blocks.map((block, index) => ({
        filename: `${index}.${getShortLang(block.lang)}`,
        text: [...block.comments, block.value, ''].join('\n'),
    }));
}
/**
 * Creates a map function that adjusts messages in a code block.
 * @param block A code block.
 * @returns A function that adjusts messages in a code block.
 */
function adjustBlock(block) {
    const leadingCommentLines = block.comments.reduce((count, comment) => count + comment.split('\n').length, 0);
    const blockStart = block.position.start.line;
    /**
     * Adjusts ESLint messages to point to the correct location in the Markdown.
     * @param message A message from ESLint.
     * @returns The same message, but adjusted to the correct location.
     */
    return function adjustMessage(message) {
        const lineInCode = message.line - leadingCommentLines;
        if (lineInCode < 1) {
            return null;
        }
        const out = {
            line: lineInCode + blockStart,
            column: message.column + block.position.indent[lineInCode - 1] - 1,
        };
        /* istanbul ignore else */
        if (Number.isInteger(message.endLine)) {
            out.endLine = message.endLine - leadingCommentLines + blockStart;
        }
        const adjustedFix = {};
        /* istanbul ignore else */
        if (message.fix) {
            adjustedFix.fix = {
                range: message.fix.range.map(range => {
                    // Advance through the block's range map to find the last
                    // matching range by finding the first range too far and
                    // then going back one.
                    let i = 1;
                    while (i < block.rangeMap.length && block.rangeMap[i].js <= range) {
                        i++;
                    }
                    // Apply the mapping delta for this range.
                    return range + block.rangeMap[i - 1].md;
                }),
                text: message.fix.text.replace(/\n/gu, `\n${block.baseIndentText}`),
            };
        }
        return Object.assign(Object.assign(Object.assign({}, message), out), adjustedFix);
    };
}
/**
 * Excludes unsatisfiable rules from the list of messages.
 * @param message A message from the linter.
 * @returns True if the message should be included in output.
 */
function excludeUnsatisfiableRules(message) {
    return message && !UNSATISFIABLE_RULES.has(message.ruleId);
}
/**
 * Transforms generated messages for output.
 * @param messages An array containing one array of messages for each code block returned from `preprocess`.
 * @param filename The filename of the file
 * @returns A flattened array of messages with mapped locations.
 */
function postprocess(messages, filename) {
    const blocks = blocksCache[filename] || [];
    // eslint-disable-next-line unicorn/prefer-spread
    return [].concat(...messages.map((group, i) => {
        const block = blocks[i];
        // non code block message, parsed by `eslint-mdx` for example
        if (!block) {
            return group;
        }
        const adjust = adjustBlock(block);
        return group.map(adjust).filter(excludeUnsatisfiableRules);
    }));
}
export const markdown = {
    preprocess,
    postprocess,
    supportsAutofix: SUPPORTS_AUTOFIX,
};
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