From 9a14b9e07c21462b85d35890d0a12712b8af31be Mon Sep 17 00:00:00 2001
From: Bryan Mishkin <698306+bmish@users.noreply.github.com>
Date: Fri, 16 Dec 2022 20:08:24 -0500
Subject: [PATCH] chore: better normalize pathRuleList option

---
 lib/generator.ts                     | 26 ++++++++++---
 lib/options.ts                       |  2 +-
 test/lib/generate/file-paths-test.ts | 57 ++++++++++++++++++++++++++++
 3 files changed, 79 insertions(+), 6 deletions(-)

diff --git a/lib/generator.ts b/lib/generator.ts
index 7fea7fbb..4202eb66 100644
--- a/lib/generator.ts
+++ b/lib/generator.ts
@@ -91,6 +91,25 @@ function stringOrArrayWithFallback<T extends string | readonly string[]>(
   return stringOrArray && stringOrArray.length > 0 ? stringOrArray : fallback;
 }
 
+function stringOrArrayToArrayWithFallback(
+  stringOrArray: undefined | string | readonly string[],
+  fallback: readonly string[]
+): readonly string[] {
+  const asArray =
+    stringOrArray instanceof Array // eslint-disable-line unicorn/no-instanceof-array -- using Array.isArray() loses type information about the array.
+      ? stringOrArray
+      : stringOrArray
+      ? [stringOrArray]
+      : [];
+  const csvStringItem = asArray.find((item) => item.includes(','));
+  if (csvStringItem) {
+    throw new Error(
+      `Provide property as array, not a CSV string: ${csvStringItem}`
+    );
+  }
+  return asArray && asArray.length > 0 ? asArray : fallback;
+}
+
 // eslint-disable-next-line complexity
 export async function generate(path: string, options?: GenerateOptions) {
   const plugin = await loadPlugin(path);
@@ -115,7 +134,7 @@ export async function generate(path: string, options?: GenerateOptions) {
     options?.initRuleDocs ?? OPTION_DEFAULTS[OPTION_TYPE.INIT_RULE_DOCS];
   const pathRuleDoc =
     options?.pathRuleDoc ?? OPTION_DEFAULTS[OPTION_TYPE.PATH_RULE_DOC];
-  const pathRuleList = stringOrArrayWithFallback(
+  const pathRuleList = stringOrArrayToArrayWithFallback(
     options?.pathRuleList,
     OPTION_DEFAULTS[OPTION_TYPE.PATH_RULE_LIST]
   );
@@ -269,10 +288,7 @@ export async function generate(path: string, options?: GenerateOptions) {
     );
   }
 
-  // eslint-disable-next-line unicorn/no-instanceof-array -- using Array.isArray() loses type information about the array.
-  for (const pathRuleListItem of pathRuleList instanceof Array
-    ? pathRuleList
-    : [pathRuleList]) {
+  for (const pathRuleListItem of pathRuleList) {
     // Find the exact filename.
     const pathToFile = getPathWithExactFileNameCasing(
       join(path, pathRuleListItem)
diff --git a/lib/options.ts b/lib/options.ts
index 4df4c05f..a27c101b 100644
--- a/lib/options.ts
+++ b/lib/options.ts
@@ -47,7 +47,7 @@ export const OPTION_DEFAULTS = {
   [OPTION_TYPE.IGNORE_DEPRECATED_RULES]: false,
   [OPTION_TYPE.INIT_RULE_DOCS]: false,
   [OPTION_TYPE.PATH_RULE_DOC]: join('docs', 'rules', '{name}.md'),
-  [OPTION_TYPE.PATH_RULE_LIST]: 'README.md',
+  [OPTION_TYPE.PATH_RULE_LIST]: ['README.md'],
   [OPTION_TYPE.POSTPROCESS]: (content: string) => content,
   [OPTION_TYPE.RULE_DOC_NOTICES]: Object.entries(
     NOTICE_TYPE_DEFAULT_PRESENCE_AND_ORDERING
diff --git a/test/lib/generate/file-paths-test.ts b/test/lib/generate/file-paths-test.ts
index b6f42fe5..90a56f3c 100644
--- a/test/lib/generate/file-paths-test.ts
+++ b/test/lib/generate/file-paths-test.ts
@@ -262,6 +262,63 @@ describe('generate (file paths)', function () {
     });
   });
 
+  describe('multiple rules lists but incorrectly using CSV string for option', function () {
+    beforeEach(function () {
+      mockFs({
+        'package.json': JSON.stringify({
+          name: 'eslint-plugin-test',
+          exports: 'index.js',
+          type: 'module',
+        }),
+
+        'index.js': `
+          export default {
+            rules: {
+              'no-foo': { meta: { }, create(context) {} },
+            },
+          };`,
+
+        'README.md':
+          '<!-- begin auto-generated rules list --><!-- end auto-generated rules list -->',
+        'rules/list.md':
+          '<!-- begin auto-generated rules list --><!-- end auto-generated rules list -->',
+        'docs/rules/no-foo.md': '',
+
+        // Needed for some of the test infrastructure to work.
+        node_modules: mockFs.load(PATH_NODE_MODULES),
+      });
+    });
+
+    afterEach(function () {
+      mockFs.restore();
+      jest.resetModules();
+    });
+
+    it('throws an error', async function () {
+      await expect(
+        generate('.', {
+          pathRuleList: `README.md,${join('rules', 'list.md')}`,
+        })
+      ).rejects.toThrow(
+        `Provide property as array, not a CSV string: README.md,${join(
+          'rules',
+          'list.md'
+        )}`
+      );
+
+      await expect(
+        generate('.', {
+          pathRuleList: [`README.md,${join('rules', 'list.md')}`],
+        })
+      ).rejects.toThrow(
+        `Provide property as array, not a CSV string: README.md,${join(
+          'rules',
+          'list.md'
+        )}`
+      );
+    });
+  });
+
   describe('empty array of rule lists (happens when CLI option is not passed)', function () {
     beforeEach(function () {
       mockFs({