fix: detect and skip ESLint AND glob patterns (nested arrays in files) (#323)

* Initial plan

* Initial plan for fixing nested arrays in files field

Co-authored-by: camc314 <18101008+camc314@users.noreply.github.com>

* Fix nested arrays in files field by flattening them

Co-authored-by: camc314 <18101008+camc314@users.noreply.github.com>

* Remove package-lock.json and add to gitignore (project uses pnpm)

Co-authored-by: camc314 <18101008+camc314@users.noreply.github.com>

* u

* Apply suggestions from code review

Signed-off-by: Cameron <cameron.clark@hey.com>

* Detect and skip ESLint AND glob patterns (nested arrays) with reporting

Co-authored-by: Sysix <3897725+Sysix@users.noreply.github.com>

* Refactor files processing logic into separate files.ts module with unit tests

Co-authored-by: Sysix <3897725+Sysix@users.noreply.github.com>

* Simplify processConfigFiles to return array directly and report nested arrays individually

Co-authored-by: Sysix <3897725+Sysix@users.noreply.github.com>

* Remove unnecessary undefined check in processConfigFiles

Co-authored-by: Sysix <3897725+Sysix@users.noreply.github.com>

* Fix lint errors: use DefaultReporter instead of inline objects in tests

Co-authored-by: Sysix <3897725+Sysix@users.noreply.github.com>

* Apply suggestion from @Sysix

Signed-off-by: Alexander S. <sysix@sysix-coding.de>

* u

---------

Signed-off-by: Cameron <cameron.clark@hey.com>
Signed-off-by: Alexander S. <sysix@sysix-coding.de>
Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: camc314 <18101008+camc314@users.noreply.github.com>
Co-authored-by: Cameron Clark <cameron.clark@hey.com>
Co-authored-by: Sysix <3897725+Sysix@users.noreply.github.com>
Co-authored-by: Alexander S. <sysix@sysix-coding.de>

Author: 3 people

src/files.spec.ts

@@ -0,0 +1,87 @@
+import { describe, expect, test } from 'vitest';
+import { processConfigFiles } from './files.js';
+import { DefaultReporter } from './reporter.js';
+
+describe('processConfigFiles', () => {
+  test('handles single string by wrapping it in an array', () => {
+    const result = processConfigFiles('**/*.js');
+
+    expect(result).toStrictEqual(['**/*.js']);
+  });
+
+  test('handles array of strings without modification', () => {
+    const result = processConfigFiles(['**/*.js', '**/*.ts']);
+
+    expect(result).toStrictEqual(['**/*.js', '**/*.ts']);
+  });
+
+  test('separates nested arrays from simple strings and reports them', () => {
+    const reporter = new DefaultReporter();
+
+    const result = processConfigFiles(
+      [
+        ['**/*.ts', '**/*.tsx'], // AND pattern - unsupported
+        '**/*.js', // Simple pattern - supported
+      ],
+      reporter
+    );
+
+    expect(result).toStrictEqual(['**/*.js']);
+
+    const reports = reporter.getReports();
+    expect(reports).toHaveLength(1);
+    expect(reports[0]).toContain('AND glob patterns');
+    expect(reports[0]).toContain('nested arrays');
+    expect(reports[0]).toContain('**/*.ts');
+  });
+
+  test('returns empty array when all files are nested arrays', () => {
+    const reporter = new DefaultReporter();
+
+    const result = processConfigFiles(
+      [
+        ['**/*.ts', '**/*.tsx'],
+        ['**/*.js', '**/*.jsx'],
+      ],
+      reporter
+    );
+
+    expect(result).toStrictEqual([]);
+
+    const reports = reporter.getReports();
+    expect(reports).toHaveLength(2);
+    expect(reports[0]).toContain('AND glob patterns');
+    expect(reports[1]).toContain('AND glob patterns');
+  });
+
+  test('handles multiple nested arrays correctly', () => {
+    const reporter = new DefaultReporter();
+
+    const result = processConfigFiles(
+      [
+        ['**/*.ts', '**/*.tsx'],
+        '**/*.js',
+        ['**/*.mjs', '**/*.cjs'],
+        '**/*.jsx',
+      ],
+      reporter
+    );
+
+    expect(result).toStrictEqual(['**/*.js', '**/*.jsx']);
+
+    const reports = reporter.getReports();
+    expect(reports).toHaveLength(2);
+    expect(reports[0]).toContain('**/*.ts');
+    expect(reports[1]).toContain('**/*.mjs');
+  });
+
+  test('does not report when no nested arrays present', () => {
+    const reporter = new DefaultReporter();
+
+    const result = processConfigFiles(['**/*.js', '**/*.ts'], reporter);
+
+    expect(result).toStrictEqual(['**/*.js', '**/*.ts']);
+
+    expect(reporter.getReports()).toHaveLength(0);
+  });
+});

src/files.ts

@@ -0,0 +1,33 @@
+import type { Reporter } from './types.js';
+
+/**
+ * Process ESLint config files field, separating simple string patterns
+ * from nested arrays (AND glob patterns which are unsupported in oxlint).
+ *
+ * @param files - The files field from ESLint config (can be string, array of strings, or array with nested arrays)
+ * @param reporter - Optional reporter to report unsupported AND patterns
+ * @returns Array of simple string patterns (valid files)
+ */
+export function processConfigFiles(
+  files: string | (string | string[])[],
+  reporter?: Reporter
+): string[] {
+  // Normalize files to an array
+  const filesArray = Array.isArray(files) ? files : [files];
+
+  // Separate nested arrays (AND patterns) from simple strings
+  const simpleFiles: string[] = [];
+
+  for (const file of filesArray) {
+    if (Array.isArray(file)) {
+      // Report nested array (AND glob pattern) as unsupported
+      reporter?.report(
+        `ESLint AND glob patterns (nested arrays in files) are not supported in oxlint: ${JSON.stringify(file)}`
+      );
+    } else {
+      simpleFiles.push(file);
+    }
+  }
+
+  return simpleFiles;
+}

src/index.ts

@@ -12,6 +12,7 @@ import {
 } from './plugins_rules.js';
 import { detectSameOverride } from './overrides.js';
 import fixForJsPlugins from './js_plugin_fixes.js';
+import { processConfigFiles } from './files.js';
 
 const buildConfig = (
   configs: Linter.Config[],
@@ -76,10 +77,15 @@ const buildConfig = (
     if (config.files === undefined) {
       targetConfig = oxlintConfig;
     } else {
+      const validFiles = processConfigFiles(config.files, options?.reporter);
+
+      // If no valid files remain after filtering nested arrays, skip this config
+      if (validFiles.length === 0) {
+        continue;
+      }
+
       targetConfig = {
-        files: (Array.isArray(config.files)
-          ? config.files
-          : [config.files]) as string[],
+        files: validFiles,
       };
       const [push, result] = detectSameOverride(oxlintConfig, targetConfig);