From 327dc809c516cb8780c021ae6d43e099b76cbc2b Mon Sep 17 00:00:00 2001
From: Kit Langton <kit.langton@gmail.com>
Date: Mon, 31 Aug 2026 11:30:57 -0400
Subject: [PATCH] refactor(core): reuse formatter file extension (#46080)

---
 packages/core/src/formatter.ts       |  5 ++---
 packages/core/test/formatter.test.ts | 28 ++++++++++++++++++++++++++++
 2 files changed, 30 insertions(+), 3 deletions(-)

diff --git a/packages/core/src/formatter.ts b/packages/core/src/formatter.ts
index 4e6bbe3c553..af17112ff16 100644
--- a/packages/core/src/formatter.ts
+++ b/packages/core/src/formatter.ts
@@ -54,9 +54,8 @@ const layer = Layer.effect(
     })
 
     const file = Effect.fn("Formatter.file")(function* (filepath: string) {
-      const matching = state
-        .get()
-        .formatters.filter((formatter) => formatter.extensions.includes(path.extname(filepath)))
+      const extension = path.extname(filepath)
+      const matching = state.get().formatters.filter((formatter) => formatter.extensions.includes(extension))
 
       for (const formatter of matching) {
         const enabled = yield* command(formatter)
diff --git a/packages/core/test/formatter.test.ts b/packages/core/test/formatter.test.ts
index 492ff7b7700..d4d9f96e242 100644
--- a/packages/core/test/formatter.test.ts
+++ b/packages/core/test/formatter.test.ts
@@ -58,6 +58,34 @@ function withFormatter<A, E, R>(
 }
 
 describe("Formatter", () => {
+  ;[
+    { file: "test.match", extension: ".match", matches: true },
+    { file: "test.other", extension: ".match", matches: false },
+    { file: "test.MATCH", extension: ".match", matches: false },
+    { file: "test.MATCH", extension: ".MATCH", matches: true },
+    { file: ".match", extension: ".match", matches: false },
+    { file: ".match", extension: "", matches: true },
+    { file: "README", extension: ".match", matches: false },
+    { file: "README", extension: "", matches: true },
+    { file: "test.part.match", extension: ".match", matches: true },
+    { file: "test.part.match", extension: ".part.match", matches: false },
+  ].forEach((entry) =>
+    it.live(`matches ${entry.file} against ${JSON.stringify(entry.extension)}: ${entry.matches}`, () =>
+      withFormatter(
+        {
+          matching: {
+            command: [process.execPath, "-e", "process.exit(0)", "$FILE"],
+            extensions: [entry.extension],
+          },
+        },
+        (formatter, directory) =>
+          Effect.gen(function* () {
+            expect(yield* formatter.file(path.join(directory, entry.file))).toBe(entry.matches)
+          }),
+      ),
+    ),
+  )
+
   it.live("does not run formatters marked as disabled in config", () =>
     withFormatter(
       {