feat(mapJson): add support for passing in json stream mapper

README.md

@@ -336,6 +336,16 @@ See also [`opts.proxy`](#opts-proxy)
 Logger object to use for logging operation details. Must have the same methods
 as `npmlog`.
 
+##### <a name="opts-map-json"></a> `opts.map-json`
+
+* Alias: `mapJson`, `mapJSON`
+* Type: Function
+* Default: undefined
+
+When using `fetch.json.stream()` (NOT `fetch.json()`), this will be passed down
+to [`JSONStream`](https://npm.im/JSONStream) as the second argument to
+`JSONStream.parse`, and can be used to transform stream data before output.
+
 ##### <a name="opts-maxsockets"></a> `opts.maxsockets`
 
 * Alias: `opts.max-sockets`

config.js

@@ -43,6 +43,9 @@ module.exports = figgyPudding({
   'log': {
     default: silentLog
   },
+  'map-json': 'mapJson',
+  'mapJSON': 'mapJson',
+  'mapJson': {},
   'max-sockets': 'maxsockets',
   'maxsockets': {
     default: 12

index.js

@@ -114,7 +114,8 @@ function fetchJSON (uri, opts) {
 
 module.exports.json.stream = fetchJSONStream
 function fetchJSONStream (uri, jsonPath, opts) {
-  const parser = JSONStream.parse(jsonPath)
+  opts = config(opts)
+  const parser = JSONStream.parse(jsonPath, opts.mapJson)
   const pt = parser.pipe(new PassThrough({objectMode: true}))
   parser.on('error', err => pt.emit('error', err))
   regFetch(uri, opts).then(res => {

test/index.js

@@ -255,6 +255,27 @@ test('fetch.json.stream()', t => {
   })
 })
 
+test('fetch.json.stream opts.mapJson', t => {
+  tnock(t, OPTS.registry).get('/hello').reply(200, {
+    a: 1,
+    b: 2,
+    c: 3
+  })
+  return getStream.array(
+    fetch.json.stream('/hello', '*', OPTS.concat({
+      mapJson (value, [key]) {
+        return [key, value]
+      }
+    }))
+  ).then(data => {
+    t.deepEqual(data, [
+      ['a', 1],
+      ['b', 2],
+      ['c', 3]
+    ], 'data mapped')
+  })
+})
+
 test('opts.ignoreBody', t => {
   tnock(t, OPTS.registry)
     .get('/hello')