Expose path of sublevel (#78)

README.md

@@ -66,6 +66,7 @@
     - [`sublevel.prefix`](#sublevelprefix)
     - [`sublevel.parent`](#sublevelparent)
     - [`sublevel.db`](#subleveldb)
+    - [`sublevel.path([local])`](#sublevelpathlocal)
   - [Hooks](#hooks)
     - [`hook = db.hooks.prewrite`](#hook--dbhooksprewrite)
       - [Example](#example)
@@ -782,7 +783,7 @@ A value iterator has the same interface as `iterator` except that its methods yi
 
 ### `sublevel`
 
-A sublevel is an instance of the `AbstractSublevel` class, which extends `AbstractLevel` and thus has the same API as documented above. Sublevels have a few additional properties.
+A sublevel is an instance of the `AbstractSublevel` class, which extends `AbstractLevel` and thus has the same API as documented above. Sublevels have a few additional properties and methods.
 
 #### `sublevel.prefix`
 
@@ -820,6 +821,24 @@ console.log(example.db === db) // true
 console.log(nested.db === db) // true
 ```
 
+#### `sublevel.path([local])`
+
+Get the path of this sublevel, which is its prefix without separators. If `local` is true, exclude path of parent database. If false (the default) then recurse to form a fully-qualified path that travels from the root database to this sublevel.
+
+```js
+const example = db.sublevel('example')
+const nested = example.sublevel('nested')
+const foo = db.sublevel(['example', 'nested', 'foo'])
+
+// Get global or local path
+console.log(nested.path()) // ['example', 'nested']
+console.log(nested.path(true)) // ['nested']
+
+// Has no intermediary sublevels, so the local option has no effect
+console.log(foo.path()) // ['example', 'nested', 'foo']
+console.log(foo.path(true)) // ['example', 'nested', 'foo']
+```
+
 ### Hooks
 
 **Hooks are experimental and subject to change without notice.**

UPGRADING.md

@@ -12,6 +12,7 @@ This document describes breaking changes and how to upgrade. For a complete list
     - [1.2. Not found](#12-not-found)
     - [1.3. Not ready](#13-not-ready)
     - [1.4. Hooks](#14-hooks)
+    - [1.5. Open before creating a chained batch](#15-open-before-creating-a-chained-batch)
   - [2. Private API](#2-private-api)
     - [2.1. Promises all the way](#21-promises-all-the-way)
     - [2.2. Ticks](#22-ticks)

lib/abstract-sublevel.js

@@ -10,6 +10,8 @@ const {
 
 const kGlobalPrefix = Symbol('prefix')
 const kLocalPrefix = Symbol('localPrefix')
+const kLocalPath = Symbol('localPath')
+const kGlobalPath = Symbol('globalPath')
 const kGlobalUpperBound = Symbol('upperBound')
 const kPrefixRange = Symbol('prefixRange')
 const kRoot = Symbol('root')
@@ -61,6 +63,8 @@ module.exports = function ({ AbstractLevel }) {
       // to change, until we add some form of preread or postread hooks.
       this[kRoot] = root
       this[kParent] = db
+      this[kLocalPath] = names
+      this[kGlobalPath] = db.prefix ? db.path().concat(names) : names
       this[kGlobalPrefix] = new MultiFormat(globalPrefix)
       this[kGlobalUpperBound] = new MultiFormat(globalUpperBound)
       this[kLocalPrefix] = new MultiFormat(localPrefix)
@@ -120,6 +124,10 @@ module.exports = function ({ AbstractLevel }) {
       return this[kParent]
     }
 
+    path (local = false) {
+      return local ? this[kLocalPath] : this[kGlobalPath]
+    }
+
     async _open (options) {
       // The parent db must open itself or be (re)opened by the user because
       // a sublevel should not initiate state changes on the rest of the db.

test/self/sublevel-test.js

@@ -75,26 +75,36 @@ test('sublevel prefix and options', function (t) {
   t.test('empty prefix', function (t) {
     const sub = new NoopLevel().sublevel('')
     t.is(sub.prefix, '!!')
+    t.same(sub.path(), [''])
     t.end()
   })
 
   t.test('prefix without options', function (t) {
     const sub = new NoopLevel().sublevel('prefix')
     t.is(sub.prefix, '!prefix!')
+    t.same(sub.path(), ['prefix'])
     t.end()
   })
 
   t.test('prefix and separator option', function (t) {
     const sub = new NoopLevel().sublevel('prefix', { separator: '%' })
     t.is(sub.prefix, '%prefix%')
+    t.same(sub.path(), ['prefix'])
     t.end()
   })
 
   t.test('array name', function (t) {
     const sub = new NoopLevel().sublevel(['a', 'b'])
-    t.is(sub.prefix, '!a!!b!')
     const alt = new NoopLevel().sublevel('a').sublevel('b')
+
+    t.is(sub.prefix, '!a!!b!')
+    t.same(sub.path(), ['a', 'b'])
+    t.same(sub.path(true), ['a', 'b'])
+
     t.is(alt.prefix, sub.prefix)
+    t.same(alt.path(), ['a', 'b'])
+    t.same(alt.path(true), ['b'])
+
     t.end()
   })
 
@@ -109,46 +119,64 @@ test('sublevel prefix and options', function (t) {
   t.test('array name with single element', function (t) {
     const sub = new NoopLevel().sublevel(['a'])
     t.is(sub.prefix, '!a!')
+    t.same(sub.path(), ['a'])
+
     const alt = new NoopLevel().sublevel('a')
     t.is(alt.prefix, sub.prefix)
+    t.same(sub.path(), alt.path())
+
     t.end()
   })
 
   t.test('array name and separator option', function (t) {
     const sub = new NoopLevel().sublevel(['a', 'b'], { separator: '%' })
     t.is(sub.prefix, '%a%%b%')
+    t.same(sub.path(), ['a', 'b'])
+
     const alt = new NoopLevel().sublevel('a', { separator: '%' }).sublevel('b', { separator: '%' })
     t.is(alt.prefix, sub.prefix)
+    t.same(alt.path(), ['a', 'b'])
+
     t.end()
   })
 
   t.test('separator is trimmed from prefix', function (t) {
     const sub1 = new NoopLevel().sublevel('!prefix')
     t.is(sub1.prefix, '!prefix!')
+    t.same(sub1.path(), ['prefix'])
 
     const sub2 = new NoopLevel().sublevel('prefix!')
     t.is(sub2.prefix, '!prefix!')
+    t.same(sub2.path(), ['prefix'])
 
     const sub3 = new NoopLevel().sublevel('!!prefix!!')
     t.is(sub3.prefix, '!prefix!')
+    t.same(sub3.path(), ['prefix'])
 
     const sub4 = new NoopLevel().sublevel('@prefix@', { separator: '@' })
     t.is(sub4.prefix, '@prefix@')
+    t.same(sub4.path(), ['prefix'])
 
     const sub5 = new NoopLevel().sublevel(['!!!a', 'b!!!'])
     t.is(sub5.prefix, '!a!!b!')
+    t.same(sub5.path(), ['a', 'b'])
 
     const sub6 = new NoopLevel().sublevel(['a@@@', '@@@b'], { separator: '@' })
     t.is(sub6.prefix, '@a@@b@')
+    t.same(sub6.path(), ['a', 'b'])
 
     t.end()
   })
 
   t.test('repeated separator can not result in empty prefix', function (t) {
     const sub1 = new NoopLevel().sublevel('!!!!')
     t.is(sub1.prefix, '!!')
+    t.same(sub1.path(), [''])
+
     const sub2 = new NoopLevel().sublevel(['!!!!', '!!!!'])
     t.is(sub2.prefix, '!!!!')
+    t.same(sub2.path(), ['', ''])
+
     t.end()
   })
 

types/abstract-sublevel.d.ts

@@ -26,6 +26,15 @@ declare class AbstractSublevel<TDatabase, TFormat, KDefault, VDefault>
    */
   get prefix (): string
 
+  /**
+   * Get the path of the sublevel, which is its prefix without separators.
+   *
+   * @param local If true, exclude path of parent database. If false (the default) then
+   * recurse to form a fully-qualified path that travels from the root database to this
+   * sublevel.
+   */
+  path (local?: boolean | undefined): string[]
+
   /**
    * Parent database. A read-only property.
    */