Propagate axios errors to stream client

Fixes issue apache#236.

When calling an *AsStream method a client needs to handle errors
raised by couch. These errors can include retrieving an attachment
that doesn't exist or querying a deleted view.

README.md

@@ -61,7 +61,7 @@ Note the minimum required version of Node.js is 10.
   - [db.fetch(docnames, [params], [callback])](#dbfetchdocnames-params-callback)
   - [db.fetchRevs(docnames, [params], [callback])](#dbfetchrevsdocnames-params-callback)
   - [db.createIndex(indexDef, [callback])](#dbcreateindexindexdef-callback)
-  - [db.changesReader...](#reading-changes-feed)
+  - [db.changesReader...](##reading-changes-feed)
 - [Partitioned database functions](#partition-functions)
   - [db.partitionInfo(partitionKey, [callback])](#dbpartitioninfopartitionkey-callback))
   - [db.partitionedList(partitionKey, [params], [callback])](#dbpartitionedlistpartitionkey-params-callback)
@@ -1031,7 +1031,9 @@ alice.attachment.get('rabbit', 'rabbit.png').then((body) => {
 ```js
 const fs = require('fs');
 
-alice.attachment.getAsStream('rabbit', 'rabbit.png').pipe(fs.createWriteStream('rabbit.png'));
+alice.attachment.getAsStream('rabbit', 'rabbit.png')
+  .on('error', (e) => console.error(e))
+  .pipe(fs.createWriteStream('rabbit.png'));
 ```
 
 ### db.attachment.destroy(docname, attname, [params], [callback])

lib/nano.js

@@ -14,6 +14,7 @@ const { URL } = require('url')
 const assert = require('assert')
 const querystring = require('qs')
 const axios = require('axios').default
+const INVALID_PARAMETERS_ERROR = new Error('Invalid parameters')
 const stream = require('stream')
 const http = require('http')
 const https = require('https')
@@ -46,7 +47,7 @@ function missing (...params) {
 }
 
 // calls the supplied callback or if not supplied, returns a rejected promise
-function callbackOrRejectError (callback, error = new Error('Invalid parameters')) {
+function callbackOrRejectError (callback, error = INVALID_PARAMETERS_ERROR) {
   if (callback) {
     return callback(error, null)
   } else {
@@ -189,6 +190,33 @@ module.exports = exports = function dbScope (cfg) {
     }
   }
 
+  function streamResponseHandler (response, req, stream) {
+    const statusCode = response.status || (response.response && response.response.status) || 500
+    if (response.isAxiosError && response.response) {
+      response = response.response
+    }
+    const message = response.statusText
+
+    const responseHeaders = Object.assign({
+      uri: req.url,
+      statusCode: statusCode
+    }, response.headers)
+
+    const error = new Error(message)
+    error.scope = 'couch'
+    error.statusCode = statusCode
+    error.request = req
+    error.headers = responseHeaders
+    error.errid = 'non_200'
+    error.name = 'Error'
+    error.description = message
+    error.reason = message
+
+    log({ err: 'couch', body: message, headers: responseHeaders })
+
+    stream.emit('error', error)
+  }
+
   function relax (opts, callback) {
     if (typeof opts === 'function') {
       callback = opts
@@ -339,7 +367,12 @@ module.exports = exports = function dbScope (cfg) {
     if (opts.stream) {
       // return the Request object for streaming
       const outStream = new stream.PassThrough()
-      axios(req).then((response) => { response.data.pipe(outStream) })
+      axios(req)
+        .then((response) => {
+          response.data.pipe(outStream)
+        }).catch(e => {
+          streamResponseHandler(e, req, outStream)
+        })
       return outStream
     } else {
       if (typeof callback === 'function') {

test/attachment.getAsStream.test.js

@@ -41,3 +41,19 @@ test('should be able to get an attachment as a stream - GET /db/id/attname - db.
       })
   })
 })
+
+test('should emit an error when stream attachment does not exist - GET /db/id/attname - db.attachment.getAsStream', () => {
+  // test GET /db/id/attname
+  nock(COUCH_URL)
+    .get('/db/id/notexists.gif')
+    .reply(404, 'Object Not Found', { 'content-type': 'application/json' })
+
+  return new Promise((resolve, reject) => {
+    const db = nano.db.use('db')
+    db.attachment.getAsStream('id', 'notexist.gif')
+      .on('error', (e) => {
+        expect(e.statusCode).toStrictEqual(404)
+        resolve()
+      })
+  })
+})