fix(email): retain paperclip files when resetting the input

tests/test_email_paperclip_files_browser.py

@@ -0,0 +1,55 @@
+"""The native FileList must survive resetting the compose file input."""
+import json
+import shutil
+import subprocess
+from pathlib import Path
+
+import pytest
+
+from tests.helpers.document_source import function_body
+
+
+@pytest.mark.parametrize("selections", [[["one.txt"]], [["one.txt", "two.csv"]], [["one.txt"], ["one.txt"]], [[]]])
+def test_compose_file_selection_survives_reset(tmp_path, selections):
+    if not shutil.which("node"):
+        pytest.skip("node not installed")
+    for name, content in [("one.txt", "Synthetic attachment one\n"), ("two.csv", 'name,value\n"fixture",2\n')]:
+        (tmp_path / name).write_text(content, encoding="utf-8")
+    script = r"""
+const fs=require('node:fs'),assert=require('node:assert/strict');
+let chromium;try{({chromium}=require('playwright'));}catch(e){if(e.code==='MODULE_NOT_FOUND')process.exit(77);throw e;}
+(async()=>{
+ const browser=await chromium.launch({headless:true});
+ try{
+  const page=await browser.newPage();const errors=[];page.on('pageerror',e=>errors.push(e.message));
+  await page.setContent('<input type="file" multiple aria-label="Compose attachments">');
+  await page.addScriptTag({content:`
+    window.uploads=[];window.finished=0;
+    async function _uploadComposeFiles(files){
+      for(const file of files)window.uploads.push({name:file.name,text:await file.text()});
+    }
+    __HANDLER__
+    document.querySelector('input').addEventListener('change',async event=>{
+      await _handleAttachUpload(event);window.finished++;
+    });
+  `});
+  const selections=JSON.parse(process.argv[1]),root=process.argv[2],expected=[];
+  for(const [index,names] of selections.entries()){
+   await page.getByLabel('Compose attachments').setInputFiles(names.map(name=>root+'/'+name));
+   await page.waitForFunction(n=>window.finished===n,index+1);
+   expected.push(...names.map(name=>({name,text:fs.readFileSync(root+'/'+name,'utf8')})));
+   assert.deepEqual(await page.evaluate(()=>window.uploads),expected);
+   assert.equal(await page.getByLabel('Compose attachments').inputValue(),'');
+   assert.equal(await page.getByLabel('Compose attachments').evaluate(el=>el.files.length),0);
+  }
+  assert.deepEqual(errors,[]);console.log(JSON.stringify({files:expected.length}));
+ }finally{await browser.close();}
+})().catch(e=>{console.error(e);process.exitCode=1;});
+""".replace("__HANDLER__", function_body("_handleAttachUpload"))
+    result = subprocess.run(["node", "-e", script, json.dumps(selections), str(tmp_path)],
+                            cwd=Path(__file__).resolve().parents[1], capture_output=True,
+                            text=True, timeout=30)
+    if result.returncode == 77:
+        pytest.skip("playwright not installed")
+    assert result.returncode == 0, result.stdout + result.stderr
+    assert json.loads(result.stdout)["files"] == sum(map(len, selections))