From aeef485dc790571b1a82ac09904329e0226b66a9 Mon Sep 17 00:00:00 2001
From: Brandon Mills <btmills@users.noreply.github.com>
Date: Mon, 26 Oct 2020 23:07:33 -0400
Subject: [PATCH] Fix: Pass internal config paths in FileEnumerator default
 (fixes #13789) (#13792)

* Chore: Repro FileEnumerator exception with default args (refs #13789)

When `CLIEngine` instantiates `FileEnumerator`, it explicitly passes its
own `CascadingConfigArrayFactory` instance, which now includes values
for `builtInRules`, `loadRules`, `eslintRecommendedPath`, and
`eslintAllPath`. This is the only place that ESLint core instantiates
`FileEnumerator`, so core does not rely on the constructor's default
value for `configArrayFactory`.

After `CascadingConfigArrayFactory` was extracted into
`@eslint/eslintrc`, it no longer assumed values for
`eslintRecommendedPath` and `eslintAllPath`, which `CLIEngine` now
provides. If those values are not passed, as is the case with the
default `CascadingConfigArrayFactory` for `configArrayFactory`, file
enumeration will encounter the exception that was reported in #13789.

From the perspective of ESLint core, the default value for
`configArrayFactory` is dead code. However, even though `FileEnumerator`
is an undocumented API, it's called by `eslint-plugin-import`'s
`no-unused-modules` rule, which hits the exception reproduced by this
test.

* Fix: Pass internal config paths in FileEnumerator default (fixes #13789)

When `CLIEngine` instantiates `FileEnumerator`, it explicitly passes its
own `CascadingConfigArrayFactory` instance, which now includes values
for `builtInRules`, `loadRules`, `eslintRecommendedPath`, and
`eslintAllPath`. This is the only place that ESLint core instantiates
`FileEnumerator`, so core does not rely on the constructor's default
value for `configArrayFactory`.

After `CascadingConfigArrayFactory` was extracted into
`@eslint/eslintrc`, it no longer assumed values for
`eslintRecommendedPath` and `eslintAllPath`, which `CLIEngine` now
provides. If those values are not passed, as is the case with the
default `CascadingConfigArrayFactory` for `configArrayFactory`, file
enumeration will encounter the exception that was reported in #13789.

From the perspective of ESLint core, the default value for
`configArrayFactory` is dead code. However, even though `FileEnumerator`
is an undocumented API, it's called by `eslint-plugin-import`'s
`no-unused-modules` rule, which hits the exception reproduced by this
test.
---
 lib/cli-engine/file-enumerator.js       |  6 +++++-
 tests/lib/cli-engine/file-enumerator.js | 27 +++++++++++++++++++++++++
 2 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/lib/cli-engine/file-enumerator.js b/lib/cli-engine/file-enumerator.js
index 446342a1a93..c2961d71ac0 100644
--- a/lib/cli-engine/file-enumerator.js
+++ b/lib/cli-engine/file-enumerator.js
@@ -213,7 +213,11 @@ class FileEnumerator {
      */
     constructor({
         cwd = process.cwd(),
-        configArrayFactory = new CascadingConfigArrayFactory({ cwd }),
+        configArrayFactory = new CascadingConfigArrayFactory({
+            cwd,
+            eslintRecommendedPath: path.resolve(__dirname, "../../conf/eslint-recommended.js"),
+            eslintAllPath: path.resolve(__dirname, "../../conf/eslint-all.js")
+        }),
         extensions = null,
         globInputPaths = true,
         errorOnUnmatchedPattern = true,
diff --git a/tests/lib/cli-engine/file-enumerator.js b/tests/lib/cli-engine/file-enumerator.js
index 1561b42e105..3ea51a408c8 100644
--- a/tests/lib/cli-engine/file-enumerator.js
+++ b/tests/lib/cli-engine/file-enumerator.js
@@ -488,4 +488,31 @@ describe("FileEnumerator", () => {
             });
         });
     });
+
+    // https://github.com/eslint/eslint/issues/13789
+    describe("constructor default values when config extends eslint:recommended", () => {
+        const root = path.join(os.tmpdir(), "eslint/file-enumerator");
+        const files = {
+            "file.js": "",
+            ".eslintrc.json": JSON.stringify({
+                extends: ["eslint:recommended"]
+            })
+        };
+        const { prepare, cleanup, getPath } = createCustomTeardown({ cwd: root, files });
+
+
+        /** @type {FileEnumerator} */
+        let enumerator;
+
+        beforeEach(async () => {
+            await prepare();
+            enumerator = new FileEnumerator({ cwd: getPath() });
+        });
+
+        afterEach(cleanup);
+
+        it("should not throw an exception iterating files", () => {
+            Array.from(enumerator.iterateFiles(["."]));
+        });
+    });
 });