fix(watcher): close deleted open documents

test/integration/watcher-gopls.test.ts

@@ -32,7 +32,7 @@ interface DiagResult {
   [serverId: string]: { diagnostics?: { message: string }[] };
 }
 
-describe("watcher: gopls picks up externally-created files", { skip: skip ?? undefined }, () => {
+describe("watcher: gopls picks up external file changes", { skip: skip ?? undefined }, () => {
   let tmpDir: string;
   let mainFile: string;
   let helperFile: string;
@@ -122,4 +122,48 @@ describe("watcher: gopls picks up externally-created files", { skip: skip ?? und
       `Expected diagnostic to clear after creating helper.go, still got: ${JSON.stringify(finalDiags)}`,
     );
   });
+
+  it("closes an opened file when it is deleted externally", async () => {
+    fs.writeFileSync(
+      helperFile,
+      "package main\n\nfunc Helper(x int) {}\n",
+    );
+    await runCliJson([helperFile, "diagnostics", '{"timeoutMs":3000}'], env);
+
+    await pollUntil(
+      async () =>
+        (await runCliJson(
+          [mainFile, "diagnostics", '{"timeoutMs":3000}'],
+          env,
+        )) as DiagResult,
+      (r) => {
+        const diags = r["gopls"]?.diagnostics ?? [];
+        return diags.some((d) => d.message.includes("not enough arguments"));
+      },
+      15000,
+      500,
+    );
+
+    fs.rmSync(helperFile);
+
+    const result = await pollUntil(
+      async () =>
+        (await runCliJson(
+          [mainFile, "diagnostics", '{"timeoutMs":3000}'],
+          env,
+        )) as DiagResult,
+      (r) => {
+        const diags = r["gopls"]?.diagnostics ?? [];
+        return diags.some((d) => d.message.toLowerCase().includes("undefined"));
+      },
+      15000,
+      500,
+    );
+
+    const finalDiags = result["gopls"]?.diagnostics ?? [];
+    assert.ok(
+      finalDiags.some((d) => d.message.toLowerCase().includes("undefined")),
+      `Expected undefined-symbol diagnostic after deleting opened helper.go, got: ${JSON.stringify(finalDiags)}`,
+    );
+  });
 });