Useful script for analyzing deno lint output. It includes utilities for grouping by code, file, search patterns, and so on.

analyze_lint.ts

// deno_package/scripts/analyze_lint.ts
import { parse } from "https://deno.land/std@0.224.0/flags/mod.ts";
import * as path from "https://deno.land/std@0.224.0/path/mod.ts";

interface LintRange {
  start: { line: number; col: number; bytePos: number };
  end: { line: number; col: number; bytePos: number };
}

interface LintDiagnostic {
  filename: string;
  range: LintRange;
  message: string;
  code: string;
  hint: string;
}

interface LintResult {
  version: number;
  diagnostics: LintDiagnostic[];
  errors: unknown[];
  checkedFiles: string[];
}

interface FilterOptions {
  codes?: string[];
  files?: string[];
  groupBy?: "code" | "file";
}

interface Stats {
  total: number;
  byCode: Record<string, number>;
  byFile: Record<string, number>;
  filesWithIssues: number;
}

function filterDiagnostics(
  diagnostics: LintDiagnostic[],
  options: FilterOptions
): LintDiagnostic[] {
  let result = diagnostics;
  
  if (options.codes) {
    const codes = new Set(options.codes);
    result = result.filter(d => codes.has(d.code));
  }
  
  if (options.files) {
    const filePatterns = options.files.map(f => new RegExp(f));
    result = result.filter(d => 
      filePatterns.some(pattern => pattern.test(d.filename))
    );
  }
  
  return result;
}

function groupDiagnostics(
  diagnostics: LintDiagnostic[],
  groupBy: "code" | "file"
): Record<string, LintDiagnostic[]> {
  const groups: Record<string, LintDiagnostic[]> = {};
  
  for (const diag of diagnostics) {
    const key = groupBy === "code" ? diag.code : diag.filename;
    if (!groups[key]) {
      groups[key] = [];
    }
    groups[key].push(diag);
  }
  
  return groups;
}

function calculateStats(diagnostics: LintDiagnostic[]): Stats {
  const byCode: Record<string, number> = {};
  const byFile: Record<string, number> = {};
  
  for (const diag of diagnostics) {
    byCode[diag.code] = (byCode[diag.code] || 0) + 1;
    byFile[diag.filename] = (byFile[diag.filename] || 0) + 1;
  }
  
  return {
    total: diagnostics.length,
    byCode,
    byFile,
    filesWithIssues: Object.keys(byFile).length
  };
}

function printStats(stats: Stats, topN: number = 10) {
  console.log("\n=== LINT ISSUE STATISTICS ===");
  console.log(`Total issues: ${stats.total}`);
  console.log(`Files with issues: ${stats.filesWithIssues}`);
  
  console.log(`\nTop ${topN} issue types:`);
  const sortedByCode = Object.entries(stats.byCode).sort((a, b) => b[1] - a[1]);
  for (let i = 0; i < Math.min(topN, sortedByCode.length); i++) {
    const [code, count] = sortedByCode[i];
    console.log(`  ${code}: ${count}`);
  }
  
  console.log(`\nTop ${topN} files with most issues:`);
  const sortedByFile = Object.entries(stats.byFile).sort((a, b) => b[1] - a[1]);
  for (let i = 0; i < Math.min(topN, sortedByFile.length); i++) {
    const [file, count] = sortedByFile[i];
    console.log(`  ${path.basename(file)}: ${count}`);
  }
}

function printGroupedDiagnostics(
  groups: Record<string, LintDiagnostic[]>,
  groupBy: "code" | "file",
  limit?: number
) {
  const sortedEntries = Object.entries(groups).sort(
    (a, b) => b[1].length - a[1].length
  );
  
  const entriesToShow = limit ? sortedEntries.slice(0, limit) : sortedEntries;
  
  for (const [key, diagnostics] of entriesToShow) {
    console.log(`\n${groupBy.toUpperCase()}: ${key} (${diagnostics.length} issues)`);
    // Show first 5 issues for each group to avoid overwhelming output
    const issuesToShow = Math.min(5, diagnostics.length);
    for (let i = 0; i < issuesToShow; i++) {
      const diag = diagnostics[i];
      console.log(
        `  ${path.basename(diag.filename)}:${diag.range.start.line + 1}:${diag.range.start.col + 1} - ${diag.message}`
      );
    }
    if (diagnostics.length > issuesToShow) {
      console.log(`  ... and ${diagnostics.length - issuesToShow} more issues`);
    }
  }
  
  if (limit && sortedEntries.length > limit) {
    console.log(`\n... and ${sortedEntries.length - limit} more groups`);
  }
}

async function runDenoLint(): Promise<LintResult> {
  const command = new Deno.Command(Deno.execPath(), {
    args: ["lint", "--json"],
    stdout: "piped",
    stderr: "piped",
  });
  
  const { code, stdout, stderr } = await command.output();
  
  if (code !== 0 && code !== 1) { // Deno lint returns 1 when there are lint issues
    const errorOutput = new TextDecoder().decode(stderr);
    throw new Error(`Lint command failed:\n${errorOutput}`);
  }
  
  const output = new TextDecoder().decode(stdout);
  return JSON.parse(output);
}

async function main() {
  const args = parse(Deno.args, {
    alias: {
      f: "file",
      c: "code",
      g: "group",
      h: "help",
      s: "stats",
      l: "limit"
    },
    string: ["file", "code", "group"],
    boolean: ["help", "stats"],
    number: ["limit"],
    default: { limit: 0 } // 0 means no limit
  });
  
  if (args.help) {
    console.log(`
Usage: deno run analyze_lint.ts [options] [lint-output.json]

Options:
  -f, --file <pattern>     Filter by file path pattern (regex, can be used multiple times)
  -c, --code <codes>       Filter by comma-separated lint codes
  -g, --group <type>       Group by "code" or "file"
  -s, --stats              Show statistics summary
  -l, --limit <number>     Limit number of groups to display when grouping
  --help                   Show this help message

Examples:
  deno run analyze_lint.ts -c no-unused-vars
  deno run analyze_lint.ts -f ".*\\.ts" -f ".*\\.tsx" -g file
  deno run analyze_lint.ts --code=no-explicit-any,verbatim-module-syntax
  deno run analyze_lint.ts --stats
  deno run analyze_lint.ts --group code --limit 5
    `);
    return;
  }
  
  let lintResult: LintResult;
  
  // Read from file or run lint command
  if (args._.length > 0) {
    const filePath = String(args._[0]);
    const content = await Deno.readTextFile(filePath);
    lintResult = JSON.parse(content);
  } else {
    lintResult = await runDenoLint();
  }
  
  // Apply filters
  const filterOptions: FilterOptions = {};
  if (args.code) {
    filterOptions.codes = args.code.split(",").map(c => c.trim());
  }
  if (args.file) {
    // Handle multiple file patterns
    filterOptions.files = Array.isArray(args.file) 
      ? args.file 
      : [args.file];
  }
  
  const filteredDiagnostics = filterDiagnostics(
    lintResult.diagnostics,
    filterOptions
  );
  
  // Show statistics if requested
  if (args.stats) {
    const stats = calculateStats(filteredDiagnostics);
    printStats(stats);
  }
  
  // Group or show all diagnostics
  if (args.group) {
    const groups = groupDiagnostics(filteredDiagnostics, args.group as "code" | "file");
    printGroupedDiagnostics(groups, args.group as "code" | "file", args.limit || undefined);
  } else if (!args.stats) {
    // Only show JSON output if neither stats nor grouping is requested
    console.log(JSON.stringify({ diagnostics: filteredDiagnostics }, null, 2));
  }
  
  if (!args.stats) {
    console.log(`\nFound ${filteredDiagnostics.length} issues matching criteria`);
  }
}

if (import.meta.main) {
  main().catch(console.error);
}