fix(lsp): prevent stale diagnostics by syncing didChange

src/tools/lsp/client.test.ts

@@ -0,0 +1,63 @@
+import { mkdtempSync, rmSync, writeFileSync } from "node:fs"
+import { join } from "node:path"
+import { tmpdir } from "node:os"
+
+import { describe, it, expect, spyOn, mock } from "bun:test"
+
+mock.module("vscode-jsonrpc/node", () => ({
+  createMessageConnection: () => {
+    throw new Error("not used in unit test")
+  },
+  StreamMessageReader: function StreamMessageReader() {},
+  StreamMessageWriter: function StreamMessageWriter() {},
+}))
+
+import { LSPClient } from "./client"
+import type { ResolvedServer } from "./types"
+
+describe("LSPClient", () => {
+  describe("openFile", () => {
+    it("sends didChange when a previously opened file changes on disk", async () => {
+      // #given
+      const dir = mkdtempSync(join(tmpdir(), "lsp-client-test-"))
+      const filePath = join(dir, "test.ts")
+      writeFileSync(filePath, "const a = 1\n")
+
+      const originalSetTimeout = globalThis.setTimeout
+      globalThis.setTimeout = ((fn: (...args: unknown[]) => void, _ms?: number) => {
+        fn()
+        return 0 as unknown as ReturnType<typeof setTimeout>
+      }) as typeof setTimeout
+
+      const server: ResolvedServer = {
+        id: "typescript",
+        command: ["typescript-language-server", "--stdio"],
+        extensions: [".ts"],
+        priority: 0,
+      }
+
+      const client = new LSPClient(dir, server)
+
+      // Stub protocol output: we only want to assert notifications.
+      const sendNotificationSpy = spyOn(
+        client as unknown as { sendNotification: (m: string, p?: unknown) => void },
+        "sendNotification"
+      )
+
+      try {
+        // #when
+        await client.openFile(filePath)
+        writeFileSync(filePath, "const a = 2\n")
+        await client.openFile(filePath)
+
+        // #then
+        const methods = sendNotificationSpy.mock.calls.map((c) => c[0])
+        expect(methods).toContain("textDocument/didOpen")
+        expect(methods).toContain("textDocument/didChange")
+      } finally {
+        globalThis.setTimeout = originalSetTimeout
+        rmSync(dir, { recursive: true, force: true })
+      }
+    })
+  })
+})