From d21ff6053e15f9320d07015c41382986bb7d5b62 Mon Sep 17 00:00:00 2001
From: nayounsang <nayounsang722@gmail.com>
Date: Thu, 5 Jun 2025 18:06:20 +0900
Subject: [PATCH 1/2] test: flatten dynamic test cases to hand-written

---
 .../tests/rules/no-base-to-string.test.ts     | 304 +++++++++++++++---
 1 file changed, 267 insertions(+), 37 deletions(-)

diff --git a/packages/eslint-plugin/tests/rules/no-base-to-string.test.ts b/packages/eslint-plugin/tests/rules/no-base-to-string.test.ts
index f0fe39979c4d..d29c5af52891 100644
--- a/packages/eslint-plugin/tests/rules/no-base-to-string.test.ts
+++ b/packages/eslint-plugin/tests/rules/no-base-to-string.test.ts
@@ -13,55 +13,285 @@ const ruleTester = new RuleTester({
   },
 });
 
-const literalListBasic: string[] = [
-  "''",
-  "'text'",
-  'true',
-  'false',
-  '1',
-  '1n',
-  '[]',
-  '/regex/',
-];
-
-const literalListNeedParen: string[] = [
-  "__dirname === 'foobar'",
-  '{}.constructor()',
-  '() => {}',
-  'function() {}',
-];
-
-const literalList = [...literalListBasic, ...literalListNeedParen];
-
-const literalListWrapped = [
-  ...literalListBasic,
-  ...literalListNeedParen.map(i => `(${i})`),
-];
+/**
+ * ref: https://github.com/typescript-eslint/typescript-eslint/issues/11043
+ * Be careful with dynamic test case generation.
+ * Iterate based on the following cases:
+ * 1. literalListBasic
+ * ```
+ [
+   "''",
+   "'text'",
+   'true',
+   'false',
+   '1',
+   '1n',
+   '[]',
+   '/regex/',
+ ];
+ * ```
+ * 2. literalListNeedParen
+ * ```
+ [
+   "__dirname === 'foobar'",
+   '{}.constructor()',
+   '() => {}',
+   'function() {}',
+ ];
+ * ```
+ */
 
 ruleTester.run('no-base-to-string', rule, {
   valid: [
     // template
-    ...literalList.map(i => `\`\${${i}}\`;`),
+    "`${''}`;",
+    "`${'text'}`;",
+    '`${true}`;',
+    '`${false}`;',
+    '`${1}`;',
+    '`${1n}`;',
+    '`${[]}`;',
+    '`${/regex/}`;',
+    "`${__dirname === 'foobar'}`;",
+    '`${{}.constructor()}`;',
+    '`${() => {}}`;',
+    '`${function () {}}`;',
 
     // operator + +=
-    ...literalListWrapped.flatMap(l =>
-      literalListWrapped.map(r => `${l} + ${r};`),
-    ),
+    "'' + '';",
+    "'' + 'text';",
+    "'' + true;",
+    "'' + false;",
+    "'' + 1;",
+    "'' + 1n;",
+    "'' + [];",
+    "'' + /regex/;",
+    "'' + (__dirname === 'foobar');",
+    "'' + {}.constructor();",
+    "'' + (() => {});",
+    "'' + function () {};",
+    "'text' + '';",
+    "'text' + 'text';",
+    "'text' + true;",
+    "'text' + false;",
+    "'text' + 1;",
+    "'text' + 1n;",
+    "'text' + [];",
+    "'text' + /regex/;",
+    "'text' + (__dirname === 'foobar');",
+    "'text' + {}.constructor();",
+    "'text' + (() => {});",
+    "'text' + function () {};",
+    "true + '';",
+    "true + 'text';",
+    'true + true;',
+    'true + false;',
+    'true + 1;',
+    'true + 1n;',
+    'true + [];',
+    'true + /regex/;',
+    "true + (__dirname === 'foobar');",
+    'true + {}.constructor();',
+    'true + (() => {});',
+    'true + function () {};',
+    "false + '';",
+    "false + 'text';",
+    'false + true;',
+    'false + false;',
+    'false + 1;',
+    'false + 1n;',
+    'false + [];',
+    'false + /regex/;',
+    "false + (__dirname === 'foobar');",
+    'false + {}.constructor();',
+    'false + (() => {});',
+    'false + function () {};',
+    "1 + '';",
+    "1 + 'text';",
+    '1 + true;',
+    '1 + false;',
+    '1 + 1;',
+    '1 + 1n;',
+    '1 + [];',
+    '1 + /regex/;',
+    "1 + (__dirname === 'foobar');",
+    '1 + {}.constructor();',
+    '1 + (() => {});',
+    '1 + function () {};',
+    "1n + '';",
+    "1n + 'text';",
+    '1n + true;',
+    '1n + false;',
+    '1n + 1;',
+    '1n + 1n;',
+    '1n + [];',
+    '1n + /regex/;',
+    "1n + (__dirname === 'foobar');",
+    '1n + {}.constructor();',
+    '1n + (() => {});',
+    '1n + function () {};',
+    "[] + '';",
+    "[] + 'text';",
+    '[] + true;',
+    '[] + false;',
+    '[] + 1;',
+    '[] + 1n;',
+    '[] + [];',
+    '[] + /regex/;',
+    "[] + (__dirname === 'foobar');",
+    '[] + {}.constructor();',
+    '[] + (() => {});',
+    '[] + function () {};',
+    "/regex/ + '';",
+    "/regex/ + 'text';",
+    '/regex/ + true;',
+    '/regex/ + false;',
+    '/regex/ + 1;',
+    '/regex/ + 1n;',
+    '/regex/ + [];',
+    '/regex/ + /regex/;',
+    "/regex/ + (__dirname === 'foobar');",
+    '/regex/ + {}.constructor();',
+    '/regex/ + (() => {});',
+    '/regex/ + function () {};',
+    "(__dirname === 'foobar') + '';",
+    "(__dirname === 'foobar') + 'text';",
+    "(__dirname === 'foobar') + true;",
+    "(__dirname === 'foobar') + false;",
+    "(__dirname === 'foobar') + 1;",
+    "(__dirname === 'foobar') + 1n;",
+    "(__dirname === 'foobar') + [];",
+    "(__dirname === 'foobar') + /regex/;",
+    "(__dirname === 'foobar') + (__dirname === 'foobar');",
+    "(__dirname === 'foobar') + {}.constructor();",
+    "(__dirname === 'foobar') + (() => {});",
+    "(__dirname === 'foobar') + function () {};",
+    "({}).constructor() + '';",
+    "({}).constructor() + 'text';",
+    '({}).constructor() + true;',
+    '({}).constructor() + false;',
+    '({}).constructor() + 1;',
+    '({}).constructor() + 1n;',
+    '({}).constructor() + [];',
+    '({}).constructor() + /regex/;',
+    "({}).constructor() + (__dirname === 'foobar');",
+    '({}).constructor() + {}.constructor();',
+    '({}).constructor() + (() => {});',
+    '({}).constructor() + function () {};',
+    "(() => {}) + '';",
+    "(() => {}) + 'text';",
+    '(() => {}) + true;',
+    '(() => {}) + false;',
+    '(() => {}) + 1;',
+    '(() => {}) + 1n;',
+    '(() => {}) + [];',
+    '(() => {}) + /regex/;',
+    "(() => {}) + (__dirname === 'foobar');",
+    '(() => {}) + {}.constructor();',
+    '(() => {}) + (() => {});',
+    '(() => {}) + function () {};',
+    "(function () {}) + '';",
+    "(function () {}) + 'text';",
+    '(function () {}) + true;',
+    '(function () {}) + false;',
+    '(function () {}) + 1;',
+    '(function () {}) + 1n;',
+    '(function () {}) + [];',
+    '(function () {}) + /regex/;',
+    "(function () {}) + (__dirname === 'foobar');",
+    '(function () {}) + {}.constructor();',
+    '(function () {}) + (() => {});',
+    '(function () {}) + function () {};',
 
     // toString()
-    ...literalListWrapped.map(i => `${i === '1' ? `(${i})` : i}.toString();`),
+    "''.toString();",
+    "'text'.toString();",
+    'true.toString();',
+    'false.toString();',
+    '(1).toString();',
+    '1n.toString();',
+    '[].toString();',
+    '/regex/.toString();',
+    "(__dirname === 'foobar').toString();",
+    '({}).constructor().toString();',
+    '(() => {}).toString();',
+    '(function () {}).toString();',
 
     // variable toString() and template
-    ...literalList.map(
-      i => `
-        let value = ${i};
-        value.toString();
-        let text = \`\${value}\`;
-      `,
-    ),
+    `
+      let value = '';
+      value.toString();
+      let text = \`\${value}\`;
+    `,
+    `
+      let value = 'text';
+      value.toString();
+      let text = \`\${value}\`;
+    `,
+    `
+      let value = true;
+      value.toString();
+      let text = \`\${value}\`;
+    `,
+    `
+      let value = false;
+      value.toString();
+      let text = \`\${value}\`;
+    `,
+    `
+      let value = 1;
+      value.toString();
+      let text = \`\${value}\`;
+    `,
+    `
+      let value = 1n;
+      value.toString();
+      let text = \`\${value}\`;
+    `,
+    `
+      let value = [];
+      value.toString();
+      let text = \`\${value}\`;
+    `,
+    `
+      let value = /regex/;
+      value.toString();
+      let text = \`\${value}\`;
+    `,
+    `
+      let value = __dirname === 'foobar';
+      value.toString();
+      let text = \`\${value}\`;
+    `,
+    `
+      let value = {}.constructor();
+      value.toString();
+      let text = \`\${value}\`;
+    `,
+    `
+      let value = () => {};
+      value.toString();
+      let text = \`\${value}\`;
+    `,
+    `
+      let value = function () {};
+      value.toString();
+      let text = \`\${value}\`;
+    `,
 
     // String()
-    ...literalList.map(i => `String(${i});`),
+    "String('');",
+    "String('text');",
+    'String(true);',
+    'String(false);',
+    'String(1);',
+    'String(1n);',
+    'String([]);',
+    'String(/regex/);',
+    "String(__dirname === 'foobar');",
+    'String({}.constructor());',
+    'String(() => {});',
+    'String(function () {});',
     `
 function someFunction() {}
 someFunction.toString();

From 03160f9ec1999e19ae613a13d82c648c45408fbe Mon Sep 17 00:00:00 2001
From: nayounsang <nayounsang722@gmail.com>
Date: Thu, 12 Jun 2025 01:53:29 +0900
Subject: [PATCH 2/2] refactor: remove dupe tc in + op

---
 .../tests/rules/no-base-to-string.test.ts     | 111 +++---------------
 1 file changed, 16 insertions(+), 95 deletions(-)

diff --git a/packages/eslint-plugin/tests/rules/no-base-to-string.test.ts b/packages/eslint-plugin/tests/rules/no-base-to-string.test.ts
index d29c5af52891..5a8cd58742ae 100644
--- a/packages/eslint-plugin/tests/rules/no-base-to-string.test.ts
+++ b/packages/eslint-plugin/tests/rules/no-base-to-string.test.ts
@@ -19,28 +19,27 @@ const ruleTester = new RuleTester({
  * Iterate based on the following cases:
  * 1. literalListBasic
  * ```
- [
-   "''",
-   "'text'",
-   'true',
-   'false',
-   '1',
-   '1n',
-   '[]',
-   '/regex/',
- ];
+[
+  "''",
+  "'text'",
+  'true',
+  'false',
+  '1',
+  '1n',
+  '[]',
+  '/regex/',
+];
  * ```
  * 2. literalListNeedParen
  * ```
- [
-   "__dirname === 'foobar'",
-   '{}.constructor()',
-   '() => {}',
-   'function() {}',
- ];
+[
+  "__dirname === 'foobar'",
+  '{}.constructor()',
+  '() => {}',
+  'function() {}',
+];
  * ```
  */
-
 ruleTester.run('no-base-to-string', rule, {
   valid: [
     // template
@@ -58,7 +57,6 @@ ruleTester.run('no-base-to-string', rule, {
     '`${function () {}}`;',
 
     // operator + +=
-    "'' + '';",
     "'' + 'text';",
     "'' + true;",
     "'' + false;",
@@ -70,8 +68,6 @@ ruleTester.run('no-base-to-string', rule, {
     "'' + {}.constructor();",
     "'' + (() => {});",
     "'' + function () {};",
-    "'text' + '';",
-    "'text' + 'text';",
     "'text' + true;",
     "'text' + false;",
     "'text' + 1;",
@@ -82,9 +78,6 @@ ruleTester.run('no-base-to-string', rule, {
     "'text' + {}.constructor();",
     "'text' + (() => {});",
     "'text' + function () {};",
-    "true + '';",
-    "true + 'text';",
-    'true + true;',
     'true + false;',
     'true + 1;',
     'true + 1n;',
@@ -94,10 +87,6 @@ ruleTester.run('no-base-to-string', rule, {
     'true + {}.constructor();',
     'true + (() => {});',
     'true + function () {};',
-    "false + '';",
-    "false + 'text';",
-    'false + true;',
-    'false + false;',
     'false + 1;',
     'false + 1n;',
     'false + [];',
@@ -106,11 +95,6 @@ ruleTester.run('no-base-to-string', rule, {
     'false + {}.constructor();',
     'false + (() => {});',
     'false + function () {};',
-    "1 + '';",
-    "1 + 'text';",
-    '1 + true;',
-    '1 + false;',
-    '1 + 1;',
     '1 + 1n;',
     '1 + [];',
     '1 + /regex/;',
@@ -118,90 +102,27 @@ ruleTester.run('no-base-to-string', rule, {
     '1 + {}.constructor();',
     '1 + (() => {});',
     '1 + function () {};',
-    "1n + '';",
-    "1n + 'text';",
-    '1n + true;',
-    '1n + false;',
-    '1n + 1;',
-    '1n + 1n;',
     '1n + [];',
     '1n + /regex/;',
     "1n + (__dirname === 'foobar');",
     '1n + {}.constructor();',
     '1n + (() => {});',
     '1n + function () {};',
-    "[] + '';",
-    "[] + 'text';",
-    '[] + true;',
-    '[] + false;',
-    '[] + 1;',
-    '[] + 1n;',
-    '[] + [];',
     '[] + /regex/;',
     "[] + (__dirname === 'foobar');",
     '[] + {}.constructor();',
     '[] + (() => {});',
     '[] + function () {};',
-    "/regex/ + '';",
-    "/regex/ + 'text';",
-    '/regex/ + true;',
-    '/regex/ + false;',
-    '/regex/ + 1;',
-    '/regex/ + 1n;',
-    '/regex/ + [];',
-    '/regex/ + /regex/;',
     "/regex/ + (__dirname === 'foobar');",
     '/regex/ + {}.constructor();',
     '/regex/ + (() => {});',
     '/regex/ + function () {};',
-    "(__dirname === 'foobar') + '';",
-    "(__dirname === 'foobar') + 'text';",
-    "(__dirname === 'foobar') + true;",
-    "(__dirname === 'foobar') + false;",
-    "(__dirname === 'foobar') + 1;",
-    "(__dirname === 'foobar') + 1n;",
-    "(__dirname === 'foobar') + [];",
-    "(__dirname === 'foobar') + /regex/;",
-    "(__dirname === 'foobar') + (__dirname === 'foobar');",
     "(__dirname === 'foobar') + {}.constructor();",
     "(__dirname === 'foobar') + (() => {});",
     "(__dirname === 'foobar') + function () {};",
-    "({}).constructor() + '';",
-    "({}).constructor() + 'text';",
-    '({}).constructor() + true;',
-    '({}).constructor() + false;',
-    '({}).constructor() + 1;',
-    '({}).constructor() + 1n;',
-    '({}).constructor() + [];',
-    '({}).constructor() + /regex/;',
-    "({}).constructor() + (__dirname === 'foobar');",
-    '({}).constructor() + {}.constructor();',
     '({}).constructor() + (() => {});',
     '({}).constructor() + function () {};',
-    "(() => {}) + '';",
-    "(() => {}) + 'text';",
-    '(() => {}) + true;',
-    '(() => {}) + false;',
-    '(() => {}) + 1;',
-    '(() => {}) + 1n;',
-    '(() => {}) + [];',
-    '(() => {}) + /regex/;',
-    "(() => {}) + (__dirname === 'foobar');",
-    '(() => {}) + {}.constructor();',
-    '(() => {}) + (() => {});',
     '(() => {}) + function () {};',
-    "(function () {}) + '';",
-    "(function () {}) + 'text';",
-    '(function () {}) + true;',
-    '(function () {}) + false;',
-    '(function () {}) + 1;',
-    '(function () {}) + 1n;',
-    '(function () {}) + [];',
-    '(function () {}) + /regex/;',
-    "(function () {}) + (__dirname === 'foobar');",
-    '(function () {}) + {}.constructor();',
-    '(function () {}) + (() => {});',
-    '(function () {}) + function () {};',
 
     // toString()
     "''.toString();",