Fix property/node detection

Adds a more robust detection method, when two parameters are provided,
betweeen whether that second value are the children of the parent node
or its properties.

Author: wooorm

index.js

@@ -177,6 +177,32 @@ function addChild(nodes, value) {
     nodes.push(value);
 }
 
+/**
+ * Check if `value` is a valid child node of
+ * `tagName`.
+ *
+ * @param {string} tagName - Parent tag-name.
+ * @param {Object} value - Node or properties like value.
+ * @return {boolean} - Whether `value` is a node.
+ */
+function isNode(tagName, value) {
+    var type = value.type;
+
+    if (tagName === 'input' || !type || typeof type !== 'string') {
+        return false;
+    }
+
+    if (typeof value.children === 'object' && 'length' in value.children) {
+        return true;
+    }
+
+    if (tagName === 'button') {
+        return type !== 'submit' && type !== 'reset' && type !== 'button';
+    }
+
+    return 'value' in value;
+}
+
 /**
  * Hyperscript compatible DSL for creating virtual HAST
  * trees.
@@ -197,11 +223,7 @@ function h(selector, properties, children) {
         (
             typeof properties === 'string' ||
             'length' in properties ||
-            // Only allow a node at the `properties`
-            // position when it isn’t an `input`, as those
-            // use HTML `type` and `value` attributes too
-            // and are void.
-            (node.tagName !== 'input' && 'type' in properties)
+            isNode(node.tagName, properties)
         )
     ) {
         children = properties;

test.js

@@ -624,7 +624,81 @@ test('hastscript', function (t) {
                 'children': []
             },
             'should *not* allow omitting `properties` for ' +
-            'an `input[type=text]`, as those are void and clash'
+            'an `input[type=text][value]`, as those are void and clash'
+        );
+
+        st.deepEqual(
+            h('a', {
+                'type': 'text/html'
+            }),
+            {
+                'type': 'element',
+                'tagName': 'a',
+                'properties': {
+                    'type': 'text/html'
+                },
+                'children': []
+            },
+            'should *not* allow omitting `properties` for ' +
+            'an `[type]`, without `value` or `children`'
+        );
+
+        st.deepEqual(
+            h('foo', {
+                'type': 'text/html',
+                'children': {
+                    'bar': 'baz'
+                }
+            }),
+            {
+                'type': 'element',
+                'tagName': 'foo',
+                'properties': {
+                    'type': 'text/html',
+                    'children': {
+                        'bar': 'baz'
+                    }
+                },
+                'children': []
+            },
+            'should *not* allow omitting `properties` when ' +
+            '`children` is not set to an array'
+        );
+
+        st.deepEqual(
+            h('button', {
+                'type': 'submit',
+                'value': 'Send'
+            }),
+            {
+                'type': 'element',
+                'tagName': 'button',
+                'properties': {
+                    'type': 'submit',
+                    'value': 'Send'
+                },
+                'children': []
+            },
+            'should *not* allow omitting `properties` when ' +
+            'a button has a valid type'
+        );
+
+        st.deepEqual(
+            h('button', {
+                'type': 'text',
+                'value': 'Send'
+            }),
+            {
+                'type': 'element',
+                'tagName': 'button',
+                'properties': {},
+                'children': [{
+                    'type': 'text',
+                    'value': 'Send'
+                }]
+            },
+            'should allow omitting `properties` when ' +
+            'a button has an invalid type'
         );
 
         st.throws(