Approval attachment uploads lose filename and show as unknown file

[rendylong]

Summary

When creating a Feishu/Lark approval instance with an attachmentV2 widget, files uploaded through lark-cli api POST /open-apis/approval/v4/files/upload are accepted and can be attached to the approval, but the approval UI displays them as unknown file because the original filename/extension is not preserved in the created approval instance.

There is also a mismatch between instances/preview and instances:

• instances/preview accepts object-shaped attachmentV2.value entries that include code, name, and type.
• instances rejects the same object-shaped values with Widget value is not string.

This makes it hard for agents/scripts to create approval instances with user-friendly attachment names.

Environment

• lark-cli version 1.0.22
• macOS
• Command path: lark-cli api ...
• Approval API: /open-apis/approval/v4/files/upload, /open-apis/approval/v4/instances/preview, /open-apis/approval/v4/instances

Reproduction

1. Upload a PDF attachment and include name and type in multipart form fields:

lark-cli api POST /open-apis/approval/v4/files/upload \
  --as bot \
  --file path/to/invoice.pdf \
  --data '{"type":"attachment","name":"invoice.pdf"}' \
  --format json

The upload succeeds and returns a file code.

2. Use the returned code in an approval attachmentV2 widget:

{
  "id": "widget_attachment",
  "type": "attachmentV2",
  "value": ["<uploaded-file-code>"]
}

3. Create the approval instance:

lark-cli api POST /open-apis/approval/v4/instances \
  --as bot \
  --data - \
  --format json < approval_request.json

The instance is created successfully, but the approval UI shows the attachment as unknown file instead of invoice.pdf.

Preview vs Create Mismatch

The preview endpoint accepts object-shaped values:

{
  "id": "widget_attachment",
  "type": "attachmentV2",
  "value": [
    {
      "code": "<uploaded-file-code>",
      "name": "invoice.pdf",
      "type": "attachment"
    }
  ]
}

This request succeeds against:

lark-cli api POST /open-apis/approval/v4/instances/preview --as bot --data -

But the create endpoint rejects the same payload:

lark-cli api POST /open-apis/approval/v4/instances --as bot --data -

Error:

Widget value is not string. index= 5, widget type= attachmentV2.

Expected Behavior

One of the following would make the workflow reliable:

1. files/upload preserves the uploaded filename/extension so approval UI displays invoice.pdf instead of unknown file.
2. instances accepts the same object-shaped attachmentV2.value that instances/preview accepts, including name and type.
3. lark-cli documents the limitation and provides a recommended way to create approval attachments with visible filenames.

Actual Behavior

• Uploaded attachments can be attached to approval instances.
• Approval UI displays the attachment as unknown file.
• Supplying a filename in files/upload --data '{"name":"..."}' does not appear to affect the displayed filename.
• Supplying object-shaped attachment values passes preview but fails create.

Workaround

For image-like attachments, converting a PDF to PNG and uploading it as type=image avoids the worst UX because the image is previewable, but this is not a good replacement for preserving the original filename for PDFs and other documents.

[rendylong]

I investigated the CLI source and this looks primarily like a lark-cli multipart construction issue, not only an Approval API limitation.

Root cause candidate:

• internal/cmdutil/fileupload.go builds generic api --file uploads via BuildFormdata.
• For local files, it currently opens the file, reads all bytes into memory, and calls fd.AddFile(fieldName, bytes.NewReader(data)).
• In github.com/larksuite/oapi-sdk-go/v3/core.Formdata.content(), multipart filenames are preserved only when the field value is a concrete *os.File; otherwise the SDK falls back to filename := "unknown-file".
• Therefore lark-cli strips the original filename before the SDK can build the multipart body, and the Approval upload endpoint receives unknown-file as the multipart filename.

Minimal local patch being tested:

- defer f.Close()
- data, err := io.ReadAll(f)
- if err != nil {
-     return nil, output.ErrValidation("--file: failed to read %s: %v", filePath, err)
- }
- fd.AddFile(fieldName, bytes.NewReader(data))
+ // Preserve concrete *os.File so the SDK can use filepath.Base(f.Name())
+ // as the multipart filename instead of falling back to "unknown-file".
+ fd.AddFile(fieldName, f)

This should allow commands like:

lark-cli api POST /open-apis/approval/v4/files/upload \
  --as bot \
  --file ./invoice.pdf \
  --data