Higher-level stream implementations can create errors in `db.attachments.insert(...)`

[sploders101]

Expected Behavior

When passing a stream as an attachment to db.attachments.insert(...), nano should stream the contents to the database regardless of the stream's implementation details.

Current Behavior

Nano uses a "poor man's deep clone" to create a copy of the request data (added in #256) before scrubbing the username and password for logging. When using a custom stream, this can create an issue where you are serializing a stream, which contains lots of circular references, and cannot be done.

Possible Solution

Implement a better scrubbing strategy. Ex:

// scrub and log
const scrubbedReq = {};
Object.entries(([key, value]) => {
  if(key !== "auth") scrubbedReq[key] = value;
});
log(scrubbedReq);

You don't need to clone the entire object. Deep cloning uses a lot of computing power for something that probably won't even end up happening. If you do a shallow clone, you can then omit the entire auth property (which might be safer if there is other authentication data in it). Data won't be modified during logging, so pass-by-reference (the issue deep cloning solves) shouldn't be an issue here.

Steps to Reproduce (for bugs)

1. Create a readable stream (ex: const myStream = fs.createReadStream(...))
2. Create a circular reference (ex: myStream.test = myStream) (many stream implementations have these for a variety of reasons).
3. Pass the req object into db.attachments.insert(...) as the data
4. A circular reference error is emitted from JSON.stringify(...)

Context

I am trying to stream an upload via ExpressJS into CouchDB and need to either patch nano or use a PassThrough stream to omit circular references being passed to CouchDB. JSON.stringify() in most cases should not be used on objects that contain classes, because a great number of class implementations contain circular references.

Your Environment

• Version used: 9.0.3
• Browser Name and version: N/A
• Operating System and version (desktop or mobile): 11.4
• Link to your project: Private Repo

[glynnbird]

Thanks @sploders101. You reasoning is very sensible: i've never liked JSON.parse(JSON.stringify(x)) and you're right than in this case it's cloning too much data.

[glynnbird]

Fixed in 9.0.4