From 4e7c9be6ff7e2448f4151563d7921cd285c2e349 Mon Sep 17 00:00:00 2001
From: Zach Kirsch <zachkirsch@users.noreply.github.com>
Date: Fri, 22 Apr 2022 10:25:21 -0700
Subject: [PATCH] fix(eslint-plugin): [no-namespace] fix false positive for
 exported namespaces when allowDeclarations=true (#4844)

* Add failing test

* Fix isDeclaration to look recursively

* Add more tests
---
 .../eslint-plugin/src/rules/no-namespace.ts   |  15 +-
 .../tests/rules/no-namespace.test.ts          | 312 ++++++++++++++++++
 2 files changed, 321 insertions(+), 6 deletions(-)

diff --git a/packages/eslint-plugin/src/rules/no-namespace.ts b/packages/eslint-plugin/src/rules/no-namespace.ts
index c8c3ff21395..c7183444e8b 100644
--- a/packages/eslint-plugin/src/rules/no-namespace.ts
+++ b/packages/eslint-plugin/src/rules/no-namespace.ts
@@ -46,12 +46,15 @@ export default util.createRule<Options, MessageIds>({
   create(context, [{ allowDeclarations, allowDefinitionFiles }]) {
     const filename = context.getFilename();
 
-    function isDeclaration(node: TSESTree.TSModuleDeclaration): boolean {
-      return (
-        node.declare === true ||
-        (node.parent!.parent?.type === AST_NODE_TYPES.TSModuleDeclaration &&
-          isDeclaration(node.parent!.parent))
-      );
+    function isDeclaration(node: TSESTree.Node): boolean {
+      if (
+        node.type === AST_NODE_TYPES.TSModuleDeclaration &&
+        node.declare === true
+      ) {
+        return true;
+      }
+
+      return node.parent != null && isDeclaration(node.parent);
     }
 
     return {
diff --git a/packages/eslint-plugin/tests/rules/no-namespace.test.ts b/packages/eslint-plugin/tests/rules/no-namespace.test.ts
index 3bb9079b3fc..11d9d1a6fca 100644
--- a/packages/eslint-plugin/tests/rules/no-namespace.test.ts
+++ b/packages/eslint-plugin/tests/rules/no-namespace.test.ts
@@ -49,6 +49,16 @@ declare namespace foo {
   namespace bar {
     namespace baz {}
   }
+}
+      `,
+      options: [{ allowDeclarations: true }],
+    },
+    {
+      code: `
+export declare namespace foo {
+  export namespace bar {
+    namespace baz {}
+  }
 }
       `,
       options: [{ allowDeclarations: true }],
@@ -251,5 +261,307 @@ namespace Foo.Bar {
         },
       ],
     },
+    {
+      code: `
+namespace A {
+  namespace B {
+    declare namespace C {}
+  }
+}
+      `,
+      errors: [
+        {
+          messageId: 'moduleSyntaxIsPreferred',
+          line: 2,
+          column: 1,
+        },
+        {
+          messageId: 'moduleSyntaxIsPreferred',
+          line: 3,
+          column: 3,
+        },
+      ],
+      options: [{ allowDeclarations: true }],
+    },
+    {
+      code: `
+namespace A {
+  namespace B {
+    export declare namespace C {}
+  }
+}
+      `,
+      errors: [
+        {
+          messageId: 'moduleSyntaxIsPreferred',
+          line: 2,
+          column: 1,
+        },
+        {
+          messageId: 'moduleSyntaxIsPreferred',
+          line: 3,
+          column: 3,
+        },
+      ],
+      options: [{ allowDeclarations: true }],
+    },
+    {
+      code: `
+namespace A {
+  declare namespace B {
+    namespace C {}
+  }
+}
+      `,
+      errors: [
+        {
+          messageId: 'moduleSyntaxIsPreferred',
+          line: 2,
+          column: 1,
+        },
+      ],
+      options: [{ allowDeclarations: true }],
+    },
+    {
+      code: `
+namespace A {
+  export declare namespace B {
+    namespace C {}
+  }
+}
+      `,
+      errors: [
+        {
+          messageId: 'moduleSyntaxIsPreferred',
+          line: 2,
+          column: 1,
+        },
+      ],
+      options: [{ allowDeclarations: true }],
+    },
+    {
+      code: `
+namespace A {
+  export declare namespace B {
+    declare namespace C {}
+  }
+}
+      `,
+      errors: [
+        {
+          messageId: 'moduleSyntaxIsPreferred',
+          line: 2,
+          column: 1,
+        },
+      ],
+      options: [{ allowDeclarations: true }],
+    },
+    {
+      code: `
+namespace A {
+  export declare namespace B {
+    export declare namespace C {}
+  }
+}
+      `,
+      errors: [
+        {
+          messageId: 'moduleSyntaxIsPreferred',
+          line: 2,
+          column: 1,
+        },
+      ],
+      options: [{ allowDeclarations: true }],
+    },
+    {
+      code: `
+namespace A {
+  declare namespace B {
+    export declare namespace C {}
+  }
+}
+      `,
+      errors: [
+        {
+          messageId: 'moduleSyntaxIsPreferred',
+          line: 2,
+          column: 1,
+        },
+      ],
+      options: [{ allowDeclarations: true }],
+    },
+    {
+      code: `
+namespace A {
+  export namespace B {
+    export declare namespace C {}
+  }
+}
+      `,
+      errors: [
+        {
+          messageId: 'moduleSyntaxIsPreferred',
+          line: 2,
+          column: 1,
+        },
+        {
+          messageId: 'moduleSyntaxIsPreferred',
+          line: 3,
+          column: 10,
+        },
+      ],
+      options: [{ allowDeclarations: true }],
+    },
+    {
+      code: `
+export namespace A {
+  namespace B {
+    declare namespace C {}
+  }
+}
+      `,
+      errors: [
+        {
+          messageId: 'moduleSyntaxIsPreferred',
+          line: 2,
+          column: 8,
+        },
+        {
+          messageId: 'moduleSyntaxIsPreferred',
+          line: 3,
+          column: 3,
+        },
+      ],
+      options: [{ allowDeclarations: true }],
+    },
+    {
+      code: `
+export namespace A {
+  namespace B {
+    export declare namespace C {}
+  }
+}
+      `,
+      errors: [
+        {
+          messageId: 'moduleSyntaxIsPreferred',
+          line: 2,
+          column: 8,
+        },
+        {
+          messageId: 'moduleSyntaxIsPreferred',
+          line: 3,
+          column: 3,
+        },
+      ],
+      options: [{ allowDeclarations: true }],
+    },
+    {
+      code: `
+export namespace A {
+  declare namespace B {
+    namespace C {}
+  }
+}
+      `,
+      errors: [
+        {
+          messageId: 'moduleSyntaxIsPreferred',
+          line: 2,
+          column: 8,
+        },
+      ],
+      options: [{ allowDeclarations: true }],
+    },
+    {
+      code: `
+export namespace A {
+  export declare namespace B {
+    namespace C {}
+  }
+}
+      `,
+      errors: [
+        {
+          messageId: 'moduleSyntaxIsPreferred',
+          line: 2,
+          column: 8,
+        },
+      ],
+      options: [{ allowDeclarations: true }],
+    },
+    {
+      code: `
+export namespace A {
+  export declare namespace B {
+    declare namespace C {}
+  }
+}
+      `,
+      errors: [
+        {
+          messageId: 'moduleSyntaxIsPreferred',
+          line: 2,
+          column: 8,
+        },
+      ],
+      options: [{ allowDeclarations: true }],
+    },
+    {
+      code: `
+export namespace A {
+  export declare namespace B {
+    export declare namespace C {}
+  }
+}
+      `,
+      errors: [
+        {
+          messageId: 'moduleSyntaxIsPreferred',
+          line: 2,
+          column: 8,
+        },
+      ],
+      options: [{ allowDeclarations: true }],
+    },
+    {
+      code: `
+export namespace A {
+  declare namespace B {
+    export declare namespace C {}
+  }
+}
+      `,
+      errors: [
+        {
+          messageId: 'moduleSyntaxIsPreferred',
+          line: 2,
+          column: 8,
+        },
+      ],
+      options: [{ allowDeclarations: true }],
+    },
+    {
+      code: `
+export namespace A {
+  export namespace B {
+    export declare namespace C {}
+  }
+}
+      `,
+      errors: [
+        {
+          messageId: 'moduleSyntaxIsPreferred',
+          line: 2,
+          column: 8,
+        },
+        {
+          messageId: 'moduleSyntaxIsPreferred',
+          line: 3,
+          column: 10,
+        },
+      ],
+      options: [{ allowDeclarations: true }],
+    },
   ],
 });