From ed42e3c222a7bd0f98090a77cfee08db366679a1 Mon Sep 17 00:00:00 2001
From: Nico Jansen <jansennico@gmail.com>
Date: Wed, 7 Oct 2020 08:29:51 +0200
Subject: [PATCH] fix(instrumenter): don't mutate generics (#2530)

Don't mutate `TSTypeParameterInstantiation` like `React.useState<true>()`
---
 packages/instrumenter/src/util/syntax-helpers.ts            | 1 +
 .../test/unit/transformers/babel-transformer.spec.ts        | 6 ++++++
 .../testResources/instrumenter/ts-declarations.ts           | 2 ++
 .../testResources/instrumenter/ts-declarations.ts.out.snap  | 3 ++-
 4 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/packages/instrumenter/src/util/syntax-helpers.ts b/packages/instrumenter/src/util/syntax-helpers.ts
index beb7c9284f..cc62c472fc 100644
--- a/packages/instrumenter/src/util/syntax-helpers.ts
+++ b/packages/instrumenter/src/util/syntax-helpers.ts
@@ -175,6 +175,7 @@ const tsTypeAnnotationNodeTypes: ReadonlyArray<types.Node['type']> = Object.free
   'TSModuleDeclaration',
   'TSEnumDeclaration',
   'TSDeclareFunction',
+  'TSTypeParameterInstantiation',
 ]);
 
 const flowTypeAnnotationNodeTypes: ReadonlyArray<types.Node['type']> = Object.freeze([
diff --git a/packages/instrumenter/test/unit/transformers/babel-transformer.spec.ts b/packages/instrumenter/test/unit/transformers/babel-transformer.spec.ts
index 00fb7e5165..72593b98ac 100644
--- a/packages/instrumenter/test/unit/transformers/babel-transformer.spec.ts
+++ b/packages/instrumenter/test/unit/transformers/babel-transformer.spec.ts
@@ -124,6 +124,12 @@ describe('babel-transformer', () => {
       expectMutateNotCalledWith((t) => t.isVariableDeclaration());
       expectMutateNotCalledWith((t) => t.isStringLiteral());
     });
+
+    it('should skip generic parameters', () => {
+      const ast = createTSAst({ rawContent: 'React.useState<string | false>()' });
+      transformBabel(ast, mutantCollectorMock, context);
+      expectMutateNotCalledWith((t) => t.isTSTypeParameterInstantiation());
+    });
   });
 
   it('should skip import declarations', () => {
diff --git a/packages/instrumenter/testResources/instrumenter/ts-declarations.ts b/packages/instrumenter/testResources/instrumenter/ts-declarations.ts
index 1aa013d314..42b4e32708 100644
--- a/packages/instrumenter/testResources/instrumenter/ts-declarations.ts
+++ b/packages/instrumenter/testResources/instrumenter/ts-declarations.ts
@@ -2,3 +2,5 @@ export declare const globalNamespace = "globalNamespace";
 declare function foo(): 'foo';
 declare module 'express' {
 }
+
+React.useState<false>();
diff --git a/packages/instrumenter/testResources/instrumenter/ts-declarations.ts.out.snap b/packages/instrumenter/testResources/instrumenter/ts-declarations.ts.out.snap
index 2933e19433..acba724781 100644
--- a/packages/instrumenter/testResources/instrumenter/ts-declarations.ts.out.snap
+++ b/packages/instrumenter/testResources/instrumenter/ts-declarations.ts.out.snap
@@ -3,5 +3,6 @@
 exports[`instrumenter integration type declarations should not produce mutants for a TS declaration file 1`] = `
 "export declare const globalNamespace = \\"globalNamespace\\";
 declare function foo(): 'foo';
-declare module 'express' {}"
+declare module 'express' {}
+React.useState<false>();"
 `;