fix(desktop): 修复导出文件下载

docs/development/Export开发说明.md

@@ -6,6 +6,8 @@
 
 Export Service 把笔记或未保存的 Markdown 文本渲染为可下载的 HTML 文件。采用与 Benchmark 一致的「创建即返回 queued、后台 asyncio.Task 执行」的内存模型，产物带 24h 过期时间，过期后不可下载。导出是轮询式（无 SSE 事件流），客户端通过 `GET /api/exports/{job_id}` 轮询状态，完成后走 `GET /api/exports/{job_id}/file` 下载。
 
+桌面端的 `core_request` 保持浏览器 Fetch 语义：JSON 响应以 UTF-8 文本传递，HTML、PDF、DOCX 等下载响应以 Base64 穿过 Tauri IPC，并在前端还原为带正确 `Content-Type` 的 `Response`。Host 将单次响应限制为 64 MiB，防止异常产物耗尽 WebView 内存。
+
 ## 模块布局
 
 ```text

frontend/src-tauri/Cargo.lock

@@ -2298,6 +2298,7 @@ checksum = "650eef8c711430f1a879fdd01d4745a7deea475becfb90269c06775983bbf086"
 name = "notesagent-desktop"
 version = "0.3.0-alpha.1"
 dependencies = [
+ "base64 0.22.1",
  "fs2",
  "reqwest 0.12.28",
  "rfd",

frontend/src-tauri/Cargo.toml

@@ -14,7 +14,7 @@ required-features = ["desktop"]
 
 [features]
 default = []
-desktop = ["dep:tauri", "dep:tauri-build", "dep:rfd", "dep:reqwest"]
+desktop = ["dep:tauri", "dep:tauri-build", "dep:rfd", "dep:reqwest", "dep:base64"]
 
 [dependencies]
 serde = { version = "1", features = ["derive"] }
@@ -27,6 +27,7 @@ fs2 = "0.4"
 tauri = { version = "2", optional = true, features = ["tray-icon"] }
 rfd = { version = "0.15", optional = true }
 reqwest = { version = "0.12", default-features = false, features = ["json", "rustls-tls"], optional = true }
+base64 = { version = "0.22", optional = true }
 
 [build-dependencies]
 tauri-build = { version = "2", optional = true , features = [] }

frontend/src-tauri/src/main.rs

@@ -2,6 +2,7 @@
 
 //! 预览 Host 只开放本地文件命令；未接通的 AI / 同步 / 凭据能力明确返回不可用。
 
+use base64::{engine::general_purpose::STANDARD as BASE64_STANDARD, Engine as _};
 use notesagent_host::recent::{RecentVault, RecentVaultStore};
 use notesagent_host::workspace::{portable_path_string, Document, Entry, Workspace};
 use std::path::Path;
@@ -47,6 +48,21 @@ struct CoreResponse {
     status: u16,
     content_type: String,
     body: String,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    body_base64: Option<String>,
+}
+
+// 后端常规导出上限为 20 MiB；为 PDF 和未来的二进制接口保留余量，同时限制 IPC 内存占用。
+const MAX_CORE_RESPONSE_BYTES: usize = 64 * 1024 * 1024;
+
+fn is_json_content_type(content_type: &str) -> bool {
+    let media_type = content_type
+        .split(';')
+        .next()
+        .unwrap_or_default()
+        .trim()
+        .to_ascii_lowercase();
+    media_type == "application/json" || media_type.ends_with("+json")
 }
 
 fn core_url(path: &str) -> Result<String, String> {
@@ -61,7 +77,7 @@ fn core_url(path: &str) -> Result<String, String> {
 
 #[cfg(test)]
 mod core_proxy_tests {
-    use super::core_url;
+    use super::{core_url, is_json_content_type};
 
     #[test]
     fn only_allows_expected_loopback_paths() {
@@ -79,6 +95,17 @@ mod core_proxy_tests {
         assert!(csp.contains("'wasm-unsafe-eval'"));
         assert!(!csp.split_whitespace().any(|token| token == "'unsafe-eval'"));
     }
+
+    #[test]
+    fn only_json_media_types_use_text_ipc_payloads() {
+        assert!(is_json_content_type("application/json; charset=utf-8"));
+        assert!(is_json_content_type("application/problem+json"));
+        assert!(!is_json_content_type("text/html; charset=utf-8"));
+        assert!(!is_json_content_type("application/pdf"));
+        assert!(!is_json_content_type(
+            "application/vnd.openxmlformats-officedocument.wordprocessingml.document"
+        ));
+    }
 }
 
 /// 预览版只代理固定回环地址，避免 WebView CORS 与任意地址转发。
@@ -120,11 +147,29 @@ async fn core_request(
         .and_then(|value| value.to_str().ok())
         .unwrap_or("")
         .to_owned();
-    let body = response.text().await.map_err(|_| "CORE_RESPONSE_ERROR")?;
+    if response
+        .content_length()
+        .is_some_and(|length| length > MAX_CORE_RESPONSE_BYTES as u64)
+    {
+        return Err("CORE_RESPONSE_TOO_LARGE".into());
+    }
+    let bytes = response.bytes().await.map_err(|_| "CORE_RESPONSE_ERROR")?;
+    if bytes.len() > MAX_CORE_RESPONSE_BYTES {
+        return Err("CORE_RESPONSE_TOO_LARGE".into());
+    }
+    let (body, body_base64) = if is_json_content_type(&content_type) {
+        (
+            String::from_utf8(bytes.to_vec()).map_err(|_| "CORE_RESPONSE_ERROR")?,
+            None,
+        )
+    } else {
+        (String::new(), Some(BASE64_STANDARD.encode(&bytes)))
+    };
     Ok(CoreResponse {
         status,
         content_type,
         body,
+        body_base64,
     })
 }
 

frontend/src/services/apiClient.desktop.spec.ts

@@ -0,0 +1,38 @@
+// @vitest-environment happy-dom
+import { beforeEach, expect, it, vi } from 'vitest'
+
+const { hostInvoke } = vi.hoisted(() => ({ hostInvoke: vi.fn() }))
+vi.mock('./platform/desktop', () => ({ isDesktop: () => true, hostInvoke }))
+
+import apiClient from './apiClient'
+
+beforeEach(() => hostInvoke.mockReset())
+
+it('restores binary desktop responses as browser-compatible response objects', async () => {
+  hostInvoke.mockResolvedValue({
+    status: 200,
+    content_type: 'application/pdf',
+    body: '',
+    body_base64: 'JVBERi0xLjc=',
+  })
+
+  const response = await apiClient.get<Response>('/api/exports/job/file')
+
+  expect(response).toBeInstanceOf(Response)
+  expect(response.headers.get('content-type')).toBe('application/pdf')
+  expect([...new Uint8Array(await response.arrayBuffer())]).toEqual([37, 80, 68, 70, 45, 49, 46, 55])
+})
+
+it('keeps downloadable text responses wrapped in a response object', async () => {
+  hostInvoke.mockResolvedValue({
+    status: 200,
+    content_type: 'text/html; charset=utf-8',
+    body: '',
+    body_base64: 'PGgxPuWvvOWHujwvaDE+',
+  })
+
+  const response = await apiClient.get<Response>('/api/exports/job/file')
+
+  expect(response).toBeInstanceOf(Response)
+  expect(await response.text()).toBe('<h1>导出</h1>')
+})

frontend/src/services/apiClient.ts

@@ -4,7 +4,26 @@ import { hostInvoke, isDesktop } from './platform/desktop'
 // 所有 HTTP 请求都经过此边界，以统一地址、请求追踪和错误契约。
 const BASE_URL = import.meta.env.VITE_API_BASE_URL ?? import.meta.env.VITE_API_BASE ?? (isDesktop() ? 'http://127.0.0.1:8000' : '')
 
-interface DesktopCoreResponse { status: number; content_type: string; body: string }
+interface DesktopCoreResponse {
+  status: number
+  content_type: string
+  body: string
+  body_base64?: string
+}
+
+function responseFromDesktopCore(response: DesktopCoreResponse): Response {
+  let body: BodyInit = response.body
+  if (response.body_base64 !== undefined) {
+    const binary = atob(response.body_base64)
+    const bytes = new Uint8Array(binary.length)
+    for (let index = 0; index < binary.length; index += 1) bytes[index] = binary.charCodeAt(index)
+    body = bytes.buffer
+  }
+  return new Response(body, {
+    status: response.status,
+    headers: response.content_type ? { 'Content-Type': response.content_type } : undefined,
+  })
+}
 
 export function resolveApiUrl(path: string): string {
   if (/^https?:\/\//i.test(path)) return path
@@ -72,7 +91,9 @@ async function request<T>(path: string, options: RequestOptions = {}): Promise<T
       })
       if (response.status >= 200 && response.status < 300) {
         if (response.status === 204) return undefined as T
-        return (response.content_type.includes('application/json') ? JSON.parse(response.body) : response.body) as T
+        return (response.content_type.includes('application/json')
+          ? JSON.parse(response.body)
+          : responseFromDesktopCore(response)) as T
       }
       let error: ErrorResponse | null = null
       try { error = JSON.parse(response.body) as ErrorResponse } catch { /* 非 JSON 错误 */ }