Merge pull request #5 from Matt-Esch/correct-vdom-thunk

correct thunk handling logic

diff.js

@@ -6,6 +6,7 @@ var isVNode = require("./is-vnode")
 var isVText = require("./is-vtext")
 var isWidget = require("./is-widget")
 var isThunk = require("./is-thunk")
+var handleThunk = require("./handle-thunk")
 
 module.exports = diff
 
@@ -16,14 +17,9 @@ function diff(a, b) {
 }
 
 function walk(a, b, patch, index) {
-    if (isThunk(b)) {
-        if (isThunk(a)) {
-            b = b.vnode = b.render(a)
-            a = a.vnode
-        } else {
-            b = b.vnode = b.render(null)
-        }
-    }
+    var nodes = handleThunk(a, b);
+    a = nodes.a
+    b = nodes.b
 
     if (a === b) {
         hooks(b, patch, index)

handle-thunk.js

@@ -0,0 +1,40 @@
+var isVNode = require('./is-vnode')
+var isVText = require('./is-vtext')
+var isWidget = require('./is-widget')
+var isThunk = require('./is-thunk')
+
+module.exports = handleThunk
+
+function handleThunk(a, b) {
+    var renderedA = a
+    var renderedB = b
+
+    if (isThunk(b)) {
+        renderedB = renderThunk(b, a)
+    }
+
+    if (isThunk(a)) {
+        renderedA = renderThunk(a, null)
+    }
+
+    return {
+        a: renderedA,
+        b: renderedB
+    }
+}
+
+function renderThunk(thunk, previous) {
+    var renderedThunk = thunk.vnode
+
+    if (!renderedThunk) {
+        renderedThunk = thunk.vnode = thunk.render(previous)
+    }
+
+    if (!(isVNode(renderedThunk) ||
+            isVText(renderedThunk) ||
+            isWidget(renderedThunk))) {
+        throw new Error("thunk did not return a valid node");
+    }
+
+    return renderedThunk
+}

package.json

@@ -1,6 +1,6 @@
 {
   "name": "vtree",
-  "version": "0.0.5",
+  "version": "0.0.13",
   "description": "a realtime tree diffing algorithm",
   "keywords": [],
   "author": "Matt Esch <[email protected]>",
@@ -21,7 +21,7 @@
     "is-object": "^0.1.2"
   },
   "devDependencies": {
-    "tape": "^2.13.1",
+    "tape": "^2.13.3",
     "virtual-dom": "0.0.10"
   },
   "licenses": [
@@ -31,7 +31,9 @@
     }
   ],
   "scripts": {
-    "test": "node ./test/index.js"
+    "test": "node ./test/index.js",
+    "cover": "istanbul cover --report none --print detail ./test/index.js",
+    "view-cover": "istanbul report html && open ./coverage/index.html"
   },
   "testling": {
     "files": "test/index.js",

test/handle-thunk.js

@@ -0,0 +1,162 @@
+var test = require("tape")
+
+var handleThunk = require("../handle-thunk")
+var VNode = require("../vnode")
+var VText = require("../vtext")
+
+test("render a new thunk to vnode", function (assert) {
+    var aNode = {
+        render: function (previous) {
+            assert.error("Render should not be called for cached thunk")
+        },
+        type: "Thunk"
+    }
+
+    aNode.vnode = new VNode("div")
+
+    var renderedBNode = new VNode("div")
+
+    var bNode = {
+        render: function (previous) {
+            assert.equal(previous, aNode)
+            return renderedBNode
+        },
+        type: "Thunk"
+    }
+
+    var result = handleThunk(aNode, bNode)
+
+    assert.equal(result.a, aNode.vnode)
+    assert.equal(result.b, renderedBNode)
+    assert.equal(bNode.vnode, renderedBNode)
+    assert.end()
+})
+
+test("render a new thunk to vtext", function (assert) {
+    var aNode = {
+        render: function (previous) {
+            assert.error("Render should not be called for cached thunk")
+        },
+        type: "Thunk"
+    }
+
+    aNode.vnode = new VNode("div")
+
+    var renderedBNode = new VText("text")
+
+    var bNode = {
+        render: function (previous) {
+            assert.equal(previous, aNode)
+            return renderedBNode
+        },
+        type: "Thunk"
+    }
+
+    var result = handleThunk(aNode, bNode)
+
+    assert.equal(result.a, aNode.vnode)
+    assert.equal(result.b, renderedBNode)
+    assert.equal(bNode.vnode, renderedBNode)
+    assert.end()
+})
+
+test("render a new thunk to a widget", function (assert) {
+    var aNode = {
+        render: function (previous) {
+            assert.error("Render should not be called for cached thunk")
+        },
+        type: "Thunk"
+    }
+
+    aNode.vnode = new VNode("div")
+
+    var renderedBNode = { type: "Widget" }
+
+    var bNode = {
+        render: function (previous) {
+            assert.equal(previous, aNode)
+            return renderedBNode
+        },
+        type: "Thunk"
+    }
+
+    var result = handleThunk(aNode, bNode)
+
+    assert.equal(result.a, aNode.vnode)
+    assert.equal(result.b, renderedBNode)
+    assert.equal(bNode.vnode, renderedBNode)
+    assert.end()
+})
+
+test("render current thunk to a thunk throws exception", function (assert) {
+    var aNode = {
+        render: function (previous) {
+            assert.error("Render should not be called for cached thunk")
+        },
+        type: "Thunk"
+    }
+
+    aNode.vnode = new VNode("div")
+
+    var bNode = {
+        render: function (previous) {
+            assert.equal(previous, aNode)
+            return { type: "Thunk" }
+        },
+        type: "Thunk"
+    }
+
+    var result
+
+    try {
+        handleThunk(aNode, bNode)
+    } catch (e) {
+        result = e
+    }
+
+    assert.equal(result.message, "thunk did not return a valid node")
+    assert.end()
+})
+
+test("render previous thunk to a thunk throws exception", function (assert) {
+    var aNode = {
+        render: function (previous) {
+            assert.equal(previous, null)
+            return { type: "Thunk" }
+        },
+        type: "Thunk"
+    }
+
+    var renderedBNode = new VNode("div")
+
+    var bNode = {
+        render: function (previous) {
+            assert.equal(previous, aNode)
+            return renderedBNode
+        },
+        type: "Thunk"
+    }
+
+    var result
+
+    try {
+        handleThunk(aNode, bNode)
+    } catch (e) {
+        result = e
+    }
+
+    assert.equal(result.message, "thunk did not return a valid node")
+    assert.end()
+})
+
+test("normal nodes are returned", function (assert) {
+    var aNode = new VNode('div')
+    var bNode = new VNode('div')
+
+    var result = handleThunk(aNode, bNode)
+
+    assert.equal(result.a, aNode)
+    assert.equal(result.b, bNode)
+    assert.end()
+})
+

test/index.js

@@ -1 +1,2 @@
 require("virtual-dom/test")
+require('./handle-thunk.js')