feat(lsp): add oxlint LSP server support (#4)

* feat(lsp): add oxlint LSP server support

Add built-in oxlint LSP server based on opencode PR #5570.

- Add OxlintServer with smart binary resolution (oxlint --lsp first,
  then oxc_language_server fallback)
- Support JS/TS and framework extensions (.vue, .astro, .svelte)
- Export OxlintServer from module
- Add comprehensive tests

Closes #3

* fix(lsp): improve error handling in OxlintServer spawn

Address PR review feedback:
- Check for ENOENT specifically in resolveBin, log other errors
- Check oxlint --help exit code before trusting output
- Add diagnostic message when neither binary is found

Author: amondnet

packages/lsp/src/__tests__/server.test.ts

@@ -3,6 +3,7 @@ import {
   LSP_SERVERS,
   TypescriptServer,
   DenoServer,
+  OxlintServer,
   PyrightServer,
   GoplsServer,
   RustAnalyzerServer,
@@ -17,6 +18,7 @@ describe("LSP_SERVERS", () => {
     const serverIds = LSP_SERVERS.map((s) => s.id);
     expect(serverIds).toContain("typescript");
     expect(serverIds).toContain("deno");
+    expect(serverIds).toContain("oxlint");
     expect(serverIds).toContain("pyright");
     expect(serverIds).toContain("gopls");
     expect(serverIds).toContain("rust-analyzer");
@@ -56,6 +58,37 @@ describe("DenoServer", () => {
   });
 });
 
+describe("OxlintServer", () => {
+  test("has correct id", () => {
+    expect(OxlintServer.id).toBe("oxlint");
+  });
+
+  test("supports JavaScript/TypeScript extensions", () => {
+    expect(OxlintServer.extensions).toContain(".ts");
+    expect(OxlintServer.extensions).toContain(".tsx");
+    expect(OxlintServer.extensions).toContain(".js");
+    expect(OxlintServer.extensions).toContain(".jsx");
+    expect(OxlintServer.extensions).toContain(".mjs");
+    expect(OxlintServer.extensions).toContain(".cjs");
+    expect(OxlintServer.extensions).toContain(".mts");
+    expect(OxlintServer.extensions).toContain(".cts");
+  });
+
+  test("supports framework-specific extensions", () => {
+    expect(OxlintServer.extensions).toContain(".vue");
+    expect(OxlintServer.extensions).toContain(".astro");
+    expect(OxlintServer.extensions).toContain(".svelte");
+  });
+
+  test("has root function", () => {
+    expect(typeof OxlintServer.root).toBe("function");
+  });
+
+  test("has spawn function", () => {
+    expect(typeof OxlintServer.spawn).toBe("function");
+  });
+});
+
 describe("PyrightServer", () => {
   test("has correct id", () => {
     expect(PyrightServer.id).toBe("pyright");

packages/lsp/src/index.ts

@@ -385,6 +385,7 @@ export {
   LSP_SERVERS,
   TypescriptServer,
   DenoServer,
+  OxlintServer,
   PyrightServer,
   GoplsServer,
   RustAnalyzerServer,

packages/lsp/src/server.ts

@@ -213,12 +213,114 @@ export const RustAnalyzerServer: LSPServerInfo = {
   },
 };
 
+/**
+ * Oxlint Language Server
+ * Based on opencode PR #5570
+ */
+export const OxlintServer: LSPServerInfo = {
+  id: "oxlint",
+  extensions: [
+    ".ts",
+    ".tsx",
+    ".js",
+    ".jsx",
+    ".mjs",
+    ".cjs",
+    ".mts",
+    ".cts",
+    ".vue",
+    ".astro",
+    ".svelte",
+  ],
+  root: nearestRoot([
+    ".oxlintrc.json",
+    "package-lock.json",
+    "bun.lockb",
+    "bun.lock",
+    "pnpm-lock.yaml",
+    "yarn.lock",
+    "package.json",
+  ]),
+  async spawn(root) {
+    const ext = process.platform === "win32" ? ".cmd" : "";
+
+    const resolveBin = async (
+      binName: string
+    ): Promise<string | undefined> => {
+      const localBin = path.join(root, "node_modules", ".bin", binName + ext);
+      try {
+        await fs.access(localBin);
+        return localBin;
+      } catch (err: unknown) {
+        // Only ignore ENOENT (file not found), log other errors
+        const isNotFound =
+          err instanceof Error &&
+          "code" in err &&
+          (err as NodeJS.ErrnoException).code === "ENOENT";
+        if (!isNotFound) {
+          console.error(`[oxlint] Cannot access local binary at ${localBin}:`, err);
+        }
+      }
+
+      // Check global PATH
+      const globalBin = Bun.which(binName);
+      if (globalBin) return globalBin;
+
+      return undefined;
+    };
+
+    // Try oxlint with --lsp flag first
+    const lintBin = await resolveBin("oxlint");
+    if (lintBin) {
+      const proc = Bun.spawn([lintBin, "--help"], {
+        stdout: "pipe",
+        stderr: "pipe",
+      });
+      const exitCode = await proc.exited;
+
+      if (exitCode !== 0) {
+        const stderr = await new Response(proc.stderr).text();
+        console.warn(
+          `[oxlint] Binary at ${lintBin} failed --help (exit ${exitCode}): ${stderr.slice(0, 200)}`
+        );
+      } else {
+        const help = await new Response(proc.stdout).text();
+        if (help.includes("--lsp")) {
+          return {
+            process: spawn(lintBin, ["--lsp"], {
+              cwd: root,
+            }),
+          };
+        }
+      }
+    }
+
+    // Fallback to oxc_language_server
+    const serverBin = await resolveBin("oxc_language_server");
+    if (serverBin) {
+      return {
+        process: spawn(serverBin, [], {
+          cwd: root,
+        }),
+      };
+    }
+
+    // Neither found - log diagnostic
+    console.warn(
+      `[oxlint] Could not start oxlint LSP server for ${root}. ` +
+        `Install with: npm install -D oxlint`
+    );
+    return undefined;
+  },
+};
+
 /**
  * All available LSP servers
  */
 export const LSP_SERVERS: LSPServerInfo[] = [
   DenoServer, // Deno first, higher priority for Deno projects
   TypescriptServer,
+  OxlintServer,
   PyrightServer,
   GoplsServer,
   RustAnalyzerServer,