Add db.getMany(keys) (#102)

Ref Level/community#101

Also adds the abstract-leveldown test suite.

This works thanks to the `encodings` option that was added to the
test suite (originally for `levelup` compatibility testing) and
changes the expected outputs (from buffers by default to strings by
default).

Author: vweevers

Diff for: index.js

@@ -84,6 +84,32 @@ DB.prototype._get = function (key, opts, cb) {
   })
 }
 
+DB.prototype._getMany = function (keys, opts, cb) {
+  keys = keys.map((key) => this.codec.encodeKey(key, opts))
+  opts.asBuffer = this.codec.valueAsBuffer(opts)
+
+  this.db.getMany(keys, opts, (err, values) => {
+    if (err) return cb(err)
+
+    const decoded = new Array(values.length)
+
+    for (let i = 0; i < values.length; i++) {
+      if (values[i] === undefined) {
+        decoded[i] = undefined
+        continue
+      }
+
+      try {
+        decoded[i] = this.codec.decodeValue(values[i], opts)
+      } catch (err) {
+        return cb(new EncodingError(err))
+      }
+    }
+
+    cb(null, decoded)
+  })
+}
+
 DB.prototype._del = function (key, opts, cb) {
   key = this.codec.encodeKey(key, opts)
   this.db.del(key, opts, cb)

Diff for: package.json

@@ -20,7 +20,7 @@
     "UPGRADING.md"
   ],
   "dependencies": {
-    "abstract-leveldown": "^7.0.0",
+    "abstract-leveldown": "^7.2.0",
     "inherits": "^2.0.3",
     "level-codec": "^10.0.0",
     "level-errors": "^3.0.0"
@@ -31,7 +31,7 @@
     "dependency-check": "^3.3.0",
     "hallmark": "^3.1.0",
     "level-community": "^3.0.0",
-    "memdown": "^6.0.0",
+    "memdown": "^6.1.0",
     "nyc": "^15.1.0",
     "standard": "^16.0.3",
     "tape": "^5.0.1"

Diff for: test/index.js

@@ -2,11 +2,33 @@
 
 const test = require('tape')
 const encdown = require('..')
+const suite = require('abstract-leveldown/test')
 const memdown = require('memdown')
 const Buffer = require('buffer').Buffer
 const hasOwnProperty = Object.prototype.hasOwnProperty
 const noop = function () {}
 
+const testCommon = suite.common({
+  test: test,
+  factory: function () {
+    return encdown(memdown())
+  },
+
+  encodings: true,
+
+  // Unsupported features
+  createIfMissing: false,
+  errorIfExists: false,
+
+  // Opt-in to new tests
+  clear: true,
+  getMany: true
+})
+
+// Test abstract-leveldown compliance
+suite(testCommon)
+
+// Custom tests
 test('opens and closes the underlying db', function (t) {
   const _db = {
     open: function (opts, cb) {
@@ -176,6 +198,64 @@ test('get() forwards error from underlying store', function (t) {
   })
 })
 
+test('getMany() skips decoding not-found values', function (t) {
+  t.plan(6)
+
+  const valueEncoding = {
+    encode: JSON.stringify,
+    decode (value) {
+      t.is(value, JSON.stringify(data))
+      return JSON.parse(value)
+    },
+    buffer: false,
+    type: 'test'
+  }
+
+  const data = { beep: 'boop' }
+  const db = encdown(memdown(), { valueEncoding })
+
+  db.open(function (err) {
+    t.error(err, 'no open() error')
+
+    db.put('foo', data, function (err) {
+      t.error(err, 'no put() error')
+
+      db.getMany(['foo', 'bar'], function (err, values) {
+        t.error(err, 'no getMany() error')
+        t.same(values, [data, undefined])
+
+        db.close(t.error.bind(t))
+      })
+    })
+  })
+})
+
+test('getMany() forwards decode error', function (t) {
+  const valueEncoding = {
+    encode: (v) => v,
+    decode: (v) => { throw new Error('decode error') },
+    buffer: false,
+    type: 'test'
+  }
+
+  const db = encdown(memdown(), { valueEncoding })
+
+  db.open(function (err) {
+    t.error(err, 'no open() error')
+
+    db.put('foo', 'bar', function (err) {
+      t.error(err, 'no put() error')
+
+      db.getMany(['foo'], function (err, values) {
+        t.is(err && err.message, 'decode error')
+        t.is(values, undefined)
+
+        db.close(t.end.bind(t))
+      })
+    })
+  })
+})
+
 test('_del() encodes key', function (t) {
   t.plan(1)