Add manifest (Level/community#83) (#351)

README.md

@@ -135,6 +135,20 @@ A read-only property. An `abstract-leveldown` compliant store can be in one of t
 - `'closing'` - waiting for the store to be closed
 - `'closed'` - store has been successfully closed, should not be used.
 
+### `db.supports`
+
+A read-only [manifest](https://github.com/Level/supports). Might be used like so:
+
+```js
+if (!db.supports.permanence) {
+  throw new Error('Persistent storage is required')
+}
+
+if (db.supports.bufferKeys && db.supports.promises) {
+  await db.put(Buffer.from('key'), 'value')
+}
+```
+
 ### `db.open([options, ]callback)`
 
 Open the store. The `callback` function will be called with no arguments when the store has been successfully opened, or with a single error argument if the open operation failed for any reason.
@@ -294,9 +308,17 @@ Support of other key and value types depends on the implementation as well as it
 
 Each of these methods will receive exactly the number and order of arguments described. Optional arguments will receive sensible defaults. All callbacks are error-first and must be asynchronous. If an operation within your implementation is synchronous, be sure to invoke the callback on a next tick using `process.nextTick(callback, ..)`, `setImmediate` or some other means of micro- or macrotask scheduling.
 
-### `db = AbstractLevelDOWN()`
+### `db = AbstractLevelDOWN([manifest])`
 
-The constructor takes no parameters. Sets the `.status` to `'new'`.
+The constructor. Sets the `.status` to `'new'`. Optionally takes a [manifest](https://github.com/Level/supports) object which `abstract-leveldown` will enrich:
+
+```js
+AbstractLevelDOWN.call(this, {
+  bufferKeys: true,
+  snapshots: true,
+  // ..
+})
+```
 
 ### `db._open(options, callback)`
 
@@ -497,6 +519,8 @@ This also serves as a signal to users of your implementation. The following opti
   - Snapshots are created asynchronously
 - `createIfMissing` and `errorIfExists`: set to `false` if `db._open()` does not support these options.
 
+This metadata will be moved to manifests (`db.supports`) in the future.
+
 ### Setup and teardown
 
 To perform (a)synchronous work before or after each test, you may define `setUp` and `tearDown` functions:

abstract-leveldown.js

@@ -1,11 +1,17 @@
 var xtend = require('xtend')
+var supports = require('level-supports')
 var AbstractIterator = require('./abstract-iterator')
 var AbstractChainedBatch = require('./abstract-chained-batch')
 var hasOwnProperty = Object.prototype.hasOwnProperty
 var rangeOptions = 'start end gt gte lt lte'.split(' ')
 
-function AbstractLevelDOWN () {
+function AbstractLevelDOWN (manifest) {
   this.status = 'new'
+
+  // TODO (next major): make this mandatory
+  this.supports = supports(manifest, {
+    status: true
+  })
 }
 
 AbstractLevelDOWN.prototype.open = function (options, callback) {

package.json

@@ -15,6 +15,7 @@
   },
   "dependencies": {
     "level-concat-iterator": "~2.0.0",
+    "level-supports": "~1.0.0",
     "xtend": "~4.0.0"
   },
   "devDependencies": {

test/common.js

@@ -13,8 +13,12 @@ function testCommon (options) {
   return {
     test: test,
     factory: factory,
+
+    // TODO (next major): remove
     setUp: options.setUp || noopTest(),
     tearDown: options.tearDown || noopTest(),
+
+    // TODO (next major): use db.supports instead
     bufferKeys: options.bufferKeys !== false,
     createIfMissing: options.createIfMissing !== false,
     errorIfExists: options.errorIfExists !== false,

test/index.js

@@ -5,6 +5,7 @@ function suite (options) {
   var test = testCommon.test
 
   require('./factory-test')(test, testCommon)
+  require('./manifest-test')(test, testCommon)
 
   require('./leveldown-test')(test, testCommon)
   require('./open-test').all(test, testCommon)

test/manifest-test.js

@@ -0,0 +1,15 @@
+var suite = require('level-supports/test')
+
+module.exports = function (test, testCommon) {
+  test('setUp common', testCommon.setUp)
+
+  suite(test, testCommon)
+
+  test('manifest has status', function (t) {
+    var db = testCommon.factory()
+    t.is(db.supports.status, true)
+    db.close(t.end.bind(t))
+  })
+
+  test('tearDown', testCommon.tearDown)
+}

test/self.js

@@ -22,7 +22,7 @@ var legacyRangeOptions = ['start', 'end']
 // excluding noop operations that can't pass the test suite.
 
 require('./leveldown-test')(test, testCommon)
-
+require('./manifest-test')(test, testCommon)
 require('./open-test').all(test, testCommon)
 
 require('./open-create-if-missing-test').setUp(test, testCommon)