From dda9cee68a5cd78b358a854027999c739ac623e9 Mon Sep 17 00:00:00 2001
From: Rafael Santana <rafaelsantana3095@gmail.com>
Date: Tue, 21 Sep 2021 03:54:56 -0300
Subject: [PATCH] fix(eslint-plugin): [no-shadow] ignore type-only imports
 properly (#3868)

---
 packages/eslint-plugin/src/rules/no-shadow.ts | 25 ++++++++--
 .../tests/rules/no-shadow.test.ts             | 46 ++++++++++++++++++-
 2 files changed, 66 insertions(+), 5 deletions(-)

diff --git a/packages/eslint-plugin/src/rules/no-shadow.ts b/packages/eslint-plugin/src/rules/no-shadow.ts
index 6eb2ef38f7c..ea27f87e083 100644
--- a/packages/eslint-plugin/src/rules/no-shadow.ts
+++ b/packages/eslint-plugin/src/rules/no-shadow.ts
@@ -1,9 +1,14 @@
 import {
-  TSESTree,
-  TSESLint,
   AST_NODE_TYPES,
+  TSESLint,
+  TSESTree,
 } from '@typescript-eslint/experimental-utils';
-import { ScopeType } from '@typescript-eslint/scope-manager';
+import {
+  Definition,
+  DefinitionType,
+  ImportBindingDefinition,
+  ScopeType,
+} from '@typescript-eslint/scope-manager';
 import * as util from '../util';
 
 type MessageIds = 'noShadow';
@@ -85,6 +90,15 @@ export default util.createRule<Options, MessageIds>({
       return variable.defs[0].type === 'Parameter' && variable.name === 'this';
     }
 
+    function isTypeImport(
+      definition: Definition,
+    ): definition is ImportBindingDefinition {
+      return (
+        definition.type === DefinitionType.ImportBinding &&
+        definition.parent.importKind === 'type'
+      );
+    }
+
     function isTypeValueShadow(
       variable: TSESLint.Scope.Variable,
       shadowed: TSESLint.Scope.Variable,
@@ -98,8 +112,11 @@ export default util.createRule<Options, MessageIds>({
         return false;
       }
 
+      const [firstDefinition] = shadowed.defs;
       const isShadowedValue =
-        'isValueVariable' in shadowed ? shadowed.isValueVariable : true;
+        !('isValueVariable' in shadowed) ||
+        !firstDefinition ||
+        (!isTypeImport(firstDefinition) && shadowed.isValueVariable);
       return variable.isValueVariable !== isShadowedValue;
     }
 
diff --git a/packages/eslint-plugin/tests/rules/no-shadow.test.ts b/packages/eslint-plugin/tests/rules/no-shadow.test.ts
index f48adfc1b57..c3e5a09f344 100644
--- a/packages/eslint-plugin/tests/rules/no-shadow.test.ts
+++ b/packages/eslint-plugin/tests/rules/no-shadow.test.ts
@@ -1,6 +1,6 @@
+import { AST_NODE_TYPES } from '@typescript-eslint/experimental-utils';
 import rule from '../../src/rules/no-shadow';
 import { RuleTester } from '../RuleTester';
-import { AST_NODE_TYPES } from '@typescript-eslint/experimental-utils';
 
 const ruleTester = new RuleTester({
   parserOptions: {
@@ -172,6 +172,18 @@ export class Wrapper<Wrapped> {
   }
 }
     `,
+    {
+      // https://github.com/typescript-eslint/typescript-eslint/issues/3862
+      code: `
+import type { foo } from './foo';
+type bar = number;
+
+// 'foo' is already declared in the upper scope
+// 'bar' is fine
+function doThing(foo: number, bar: number) {}
+      `,
+      options: [{ ignoreTypeValueShadow: true }],
+    },
   ],
   invalid: [
     {
@@ -1398,5 +1410,37 @@ function foo(cb) {
         },
       ],
     },
+    {
+      code: `
+import type { foo } from './foo';
+function doThing(foo: number, bar: number) {}
+      `,
+      options: [{ ignoreTypeValueShadow: false }],
+      errors: [
+        {
+          messageId: 'noShadow',
+          data: { name: 'foo' },
+          type: AST_NODE_TYPES.Identifier,
+          line: 3,
+          column: 18,
+        },
+      ],
+    },
+    {
+      code: `
+import { foo } from './foo';
+function doThing(foo: number, bar: number) {}
+      `,
+      options: [{ ignoreTypeValueShadow: true }],
+      errors: [
+        {
+          messageId: 'noShadow',
+          data: { name: 'foo' },
+          type: AST_NODE_TYPES.Identifier,
+          line: 3,
+          column: 18,
+        },
+      ],
+    },
   ],
 });