From 20a7dcc808a39cd447d6e52fc5a1e1373d7122e9 Mon Sep 17 00:00:00 2001
From: Gabriel Cangussu <gabrielcangussu@gmail.com>
Date: Thu, 3 Sep 2020 03:22:09 -0300
Subject: [PATCH] fix(scope-manager): fallback to lib 'esnext' or 'es5' when
 ecma version is unsupported (#2474)

---
 packages/scope-manager/src/analyze.ts         |  9 ++--
 .../eslint-scope/map-ecma-version.test.ts     | 45 +++++++++++++++++++
 2 files changed, 49 insertions(+), 5 deletions(-)
 create mode 100644 packages/scope-manager/tests/eslint-scope/map-ecma-version.test.ts

diff --git a/packages/scope-manager/src/analyze.ts b/packages/scope-manager/src/analyze.ts
index 2c7e3949176..ee3ac77de96 100644
--- a/packages/scope-manager/src/analyze.ts
+++ b/packages/scope-manager/src/analyze.ts
@@ -2,6 +2,7 @@ import { TSESTree, EcmaVersion, Lib } from '@typescript-eslint/types';
 import { visitorKeys } from '@typescript-eslint/visitor-keys';
 import { Referencer, ReferencerOptions } from './referencer';
 import { ScopeManager } from './ScopeManager';
+import { lib as TSLibraries } from './lib';
 
 ////////////////////////////////////////////////////
 // MAKE SURE THIS IS KEPT IN SYNC WITH THE README //
@@ -61,12 +62,10 @@ function mapEcmaVersion(version: EcmaVersion | undefined): Lib {
     return 'es5';
   }
 
-  if (version > 2000) {
-    return `es${version}` as Lib;
-  }
+  const year = version > 2000 ? version : 2015 + (version - 6);
+  const lib = `es${year}`;
 
-  const year = 2015 + (version - 6);
-  return `es${year}` as Lib;
+  return lib in TSLibraries ? (lib as Lib) : year > 2020 ? 'esnext' : 'es5';
 }
 
 /**
diff --git a/packages/scope-manager/tests/eslint-scope/map-ecma-version.test.ts b/packages/scope-manager/tests/eslint-scope/map-ecma-version.test.ts
new file mode 100644
index 00000000000..3a5957b7003
--- /dev/null
+++ b/packages/scope-manager/tests/eslint-scope/map-ecma-version.test.ts
@@ -0,0 +1,45 @@
+import { analyze } from '../../src/analyze';
+import { Referencer } from '../../src/referencer';
+import { TSESTree, EcmaVersion, Lib } from '@typescript-eslint/types';
+
+jest.mock('../../src/referencer');
+jest.mock('../../src/ScopeManager');
+
+describe('ecma version mapping', () => {
+  it("should map to 'esnext' when unsuported and new", () => {
+    expectMapping(2042, 'esnext');
+    expectMapping(42, 'esnext');
+  });
+
+  it("should map to 'es5' when unsuported and old", () => {
+    expectMapping(2002, 'es5');
+    expectMapping(2, 'es5');
+  });
+
+  it("should map to 'es{year}' when supported and >= 6", () => {
+    expectMapping(2015, 'es2015');
+    expectMapping(6, 'es2015');
+    expectMapping(2020, 'es2020');
+    expectMapping(11, 'es2020');
+  });
+
+  it("should map to 'es5' when 5 or 3", () => {
+    expectMapping(5, 'es5');
+    expectMapping(3, 'es5');
+  });
+
+  it("should map to 'es2018' when undefined", () => {
+    expectMapping(undefined, 'es2018');
+  });
+});
+
+const fakeNode = ({} as unknown) as TSESTree.Node;
+
+function expectMapping(ecmaVersion: number | undefined, lib: Lib): void {
+  (Referencer as jest.Mock).mockClear();
+  analyze(fakeNode, { ecmaVersion: ecmaVersion as EcmaVersion });
+  expect(Referencer).toHaveBeenCalledWith(
+    expect.objectContaining({ lib: [lib] }),
+    expect.any(Object),
+  );
+}