Implements support for promise based migrations.

lib/migrate.js

@@ -26,9 +26,14 @@ function migrate (set, direction, migrationName, fn) {
     }
 
     set.emit('migration', migration, direction)
-    migration[direction](function (err) {
-      if (err) return fn(err)
+    let migrationCompleted = false
 
+    let migrationPromise = migration[direction](function (err) {
+      if (migrationCompleted) {
+        return fn(new Error('Migration was already run. Please provide callback OR promise, not both.'))
+      }
+      if (err) return fn(err)
+      migrationCompleted = true
       // Set timestamp if running up, clear it if down
       migration.timestamp = direction === 'up' ? Date.now() : null
 
@@ -42,6 +47,30 @@ function migrate (set, direction, migrationName, fn) {
         next(migrations.shift())
       })
     })
+
+    if (migrationPromise && migrationPromise.then) {
+      migrationPromise
+        .then(function () {
+          if (migrationCompleted) {
+            return fn(new Error('Migration was already run. Please provide callback OR promise, not both.'))
+          }
+
+          migrationCompleted = true
+          // Set timestamp if running up, clear it if down
+          migration.timestamp = direction === 'up' ? Date.now() : null
+
+          // Decrement last run index
+          lastRunIndex--
+
+          set.lastRun = direction === 'up' ? migration.title : set.migrations[lastRunIndex] && set.migrations[lastRunIndex].title
+          set.save(function (err) {
+            if (err) return fn(err)
+
+            next(migrations.shift())
+          })
+        })
+        .catch(fn)
+    }
   }
 
   next(migrations.shift())

test/fixtures/promises/1-callback-test.js

@@ -0,0 +1,13 @@
+'use strict'
+
+module.exports.up = function (next) {
+  setTimeout(function () {
+    return next()
+  }, 200)
+}
+
+module.exports.down = function (next) {
+  setTimeout(function () {
+    return next()
+  }, 200)
+}

test/fixtures/promises/2-promise-test.js

@@ -0,0 +1,17 @@
+'use strict'
+
+module.exports.up = function () {
+  return new Promise(function (resolve, reject) {
+    setTimeout(function () {
+      return resolve()
+    }, 200)
+  })
+}
+
+module.exports.down = function () {
+  return new Promise(function (resolve, reject) {
+    setTimeout(function () {
+      return resolve()
+    }, 200)
+  })
+}

test/fixtures/promises/3-failure-test.js

@@ -0,0 +1,19 @@
+'use strict'
+
+module.exports.up = function (next) {
+  return new Promise(function (resolve, reject) {
+    setTimeout(function () {
+      next()
+      return resolve()
+    }, 200)
+  })
+}
+
+module.exports.down = function (next) {
+  return new Promise(function (resolve, reject) {
+    setTimeout(function () {
+      next()
+      return resolve()
+    }, 200)
+  })
+}

test/promises.js

@@ -0,0 +1,56 @@
+/* global describe, it, beforeEach, afterEach */
+
+var rimraf = require('rimraf')
+var path = require('path')
+var assert = require('assert')
+
+var migrate = require('../')
+
+var BASE = path.join(__dirname, 'fixtures', 'promises')
+var STATE = path.join(__dirname, 'fixtures', '.migrate')
+
+describe('Promise migrations', function () {
+  var set
+
+  beforeEach(function (done) {
+    migrate.load({
+      stateStore: STATE,
+      migrationsDirectory: BASE
+    }, function (err, s) {
+      set = s
+      done(err)
+    })
+  })
+
+  it('should handle callback migration', function (done) {
+    set.up('1-callback-test.js', function (err) {
+      assert.ifError(err)
+      done()
+    })
+  })
+
+  it('should handle promise migration', function (done) {
+    set.up('2-promise-test.js', function (err) {
+      assert.ifError(err)
+      done()
+    })
+  })
+
+  it('should error when using promise + callback', function (done) {
+    let errorThrown = false
+    set.up('3-failure-test.js', function (err) {
+      if (errorThrown) {
+        return
+      }
+
+      assert(err)
+      assert.equal(err.message, 'Migration was already run. Please provide callback OR promise, not both.')
+      errorThrown = true
+      done()
+    })
+  })
+
+  afterEach(function (done) {
+    rimraf(STATE, done)
+  })
+})