fix: store emitted events and re-emit them for late listeners (#39)

Author: nlf

lib/index.js

@@ -30,6 +30,10 @@ const getOptString = options => !options || !options.length
 
 const _onEnd = Symbol('_onEnd')
 const _getOptions = Symbol('_getOptions')
+const _emittedSize = Symbol('_emittedSize')
+const _emittedIntegrity = Symbol('_emittedIntegrity')
+const _emittedVerified = Symbol('_emittedVerified')
+
 class IntegrityStream extends MiniPass {
   constructor (opts) {
     super()
@@ -63,6 +67,22 @@ class IntegrityStream extends MiniPass {
     this.optString = getOptString(options)
   }
 
+  on (ev, handler) {
+    if (ev === 'size' && this[_emittedSize]) {
+      return handler(this[_emittedSize])
+    }
+
+    if (ev === 'integrity' && this[_emittedIntegrity]) {
+      return handler(this[_emittedIntegrity])
+    }
+
+    if (ev === 'verified' && this[_emittedVerified]) {
+      return handler(this[_emittedVerified])
+    }
+
+    return super.on(ev, handler)
+  }
+
   emit (ev, data) {
     if (ev === 'end') {
       this[_onEnd]()
@@ -103,9 +123,14 @@ class IntegrityStream extends MiniPass {
       err.sri = this.sri
       this.emit('error', err)
     } else {
+      this[_emittedSize] = this.size
       this.emit('size', this.size)
+      this[_emittedIntegrity] = newSri
       this.emit('integrity', newSri)
-      match && this.emit('verified', match)
+      if (match) {
+        this[_emittedVerified] = match
+        this.emit('verified', match)
+      }
     }
   }
 }

test/integrity-stream.js

@@ -4,10 +4,28 @@ const test = require('tap').test
 
 const ssri = require('..')
 
-test('generates integrity', t => {
+test('works with no options', t => {
   const TARGET = ssri.fromData('foo')
   const stream = ssri.integrityStream()
   stream.write('foo')
+  let integrity
+  stream.on('integrity', i => {
+    integrity = i
+  })
+
+  stream.on('end', () => {
+    t.same(integrity, TARGET, 'matching integrity emitted')
+    t.end()
+  })
+
+  stream.resume()
+  stream.end()
+})
+
+test('generates integrity', t => {
+  const TARGET = ssri.fromData('foo')
+  const stream = ssri.integrityStream({ integrity: TARGET })
+  stream.write('foo')
   let collected = ''
   stream.on('data', d => {
     collected += d.toString()
@@ -16,9 +34,54 @@ test('generates integrity', t => {
   stream.on('integrity', i => {
     integrity = i
   })
+  let size
+  stream.on('size', s => {
+    size = s
+  })
+  let verified
+  stream.on('verified', v => {
+    verified = v
+  })
+  stream.on('end', () => {
+    t.equal(collected, 'foo', 'stream output is complete')
+    t.equal(size, 3, 'size emitted')
+    t.same(integrity, TARGET, 'matching integrity emitted')
+    t.same(verified, TARGET.sha512[0], 'verified emitted')
+    t.end()
+  })
+  stream.end()
+})
+
+test('re-emits for late listeners', t => {
+  const TARGET = ssri.fromData('foo')
+  const stream = ssri.integrityStream({ integrity: TARGET })
+  stream.write('foo')
+  let collected = ''
+  stream.on('data', d => {
+    collected += d.toString()
+  })
+
   stream.on('end', () => {
+    // we add the listeners _after_ the end event this time to ensure that the events
+    // get emitted again for late listeners
+    let integrity
+    stream.on('integrity', i => {
+      integrity = i
+    })
+
+    let size
+    stream.on('size', s => {
+      size = s
+    })
+
+    let verified
+    stream.on('verified', v => {
+      verified = v
+    })
     t.equal(collected, 'foo', 'stream output is complete')
+    t.equal(size, 3, 'size emitted')
     t.same(integrity, TARGET, 'matching integrity emitted')
+    t.same(verified, TARGET.sha512[0], 'verified emitted')
     t.end()
   })
   stream.end()