From 9d684eec1dfc5f05353882e374f5731bf779767c Mon Sep 17 00:00:00 2001
From: Tom Kirkpatrick <tom@systemseed.com>
Date: Tue, 5 Sep 2017 09:53:54 +0200
Subject: [PATCH] fix: do not store computed properties

---
 .gitignore      |  1 +
 lib/computed.js | 16 ++++++++++++++++
 test/test.js    | 30 ++++++++++++++++++++++++++++--
 3 files changed, 45 insertions(+), 2 deletions(-)

diff --git a/.gitignore b/.gitignore
index 1fd04da..66fc60c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,4 @@
 node_modules
+db.json
 coverage
 .nyc_output
diff --git a/lib/computed.js b/lib/computed.js
index 4fd4a36..c1b2e45 100644
--- a/lib/computed.js
+++ b/lib/computed.js
@@ -42,4 +42,20 @@ module.exports = (Model, options) => {
         .then(value => (ctx.data[property] = value))
     })
   })
+
+  // The loaded observer is triggered when an item is loaded
+  Model.observe('before save', (ctx, next) => {
+    Object.keys(options.properties || {}).forEach(property => {
+      debug('Removing computed property %s', property)
+
+      if (ctx.instance) {
+        ctx.instance.unsetAttribute(property)
+      }
+      if (ctx.data) {
+        delete ctx.data[property]
+      }
+    })
+
+    return next()
+  })
 }
diff --git a/test/test.js b/test/test.js
index 096e893..7ea5e6b 100644
--- a/test/test.js
+++ b/test/test.js
@@ -11,8 +11,11 @@ const app = loopback()
 // import our mixin.
 require('../lib')(app)
 
-// Connect to db.
-const dbConnector = loopback.memory()
+// Create datasource.
+const dbConnector = loopback.createDataSource({
+  connector: loopback.Memory,
+  file: 'db.json',
+})
 
 const now = new Date()
 
@@ -49,6 +52,10 @@ describe('loopback computed property', function() {
 
   lt.beforeEach.withApp(app)
 
+  before(function() {
+    return Item.destroyAll()
+  })
+
   before(function(done) {
     new lt.TestDataBuilder()
       .define('itemOne', Item, {
@@ -80,4 +87,23 @@ describe('loopback computed property', function() {
     expect(this.itemOne.promised).to.equal('Item 1: As promised I get back to you!')
     expect(this.itemTwo.promised).to.equal('Item 2: As promised I get back to you!')
   })
+
+  it('should not store the computed property', function() {
+    return this.itemOne.updateAttributes({ readonly: false })
+      .then(item => {
+        /* eslint global-require: 0 */
+        const db = require('../db.json')
+        const itemFromDb = JSON.parse(db.models.item[item.id])
+
+        expect(item).to.have.property('readonly', true)
+        expect(item).to.have.property('requestedAt')
+        expect(item).to.have.property('promised')
+
+        expect(itemFromDb).to.have.property('id', item.id)
+        expect(itemFromDb).to.have.property('name', 'Item 1')
+        expect(itemFromDb).to.not.have.property('readonly')
+        expect(itemFromDb).to.not.have.property('requestedAt')
+        expect(itemFromDb).to.not.have.property('promised')
+      })
+  })
 })