Preserve ordering of classes

Cargo.toml

@@ -23,6 +23,7 @@ anymap = "0.12"
 bincode = "=1.0.1"
 failure = "0.1"
 http = "0.1"
+indexmap = "1.0.2"
 log = "0.4"
 proc-macro-hack = "0.5"
 proc-macro-nested = "0.1"

src/virtual_dom/mod.rs

@@ -6,9 +6,10 @@ pub mod vnode;
 pub mod vtag;
 pub mod vtext;
 
-use std::collections::{HashMap, HashSet};
+use std::collections::HashMap;
 use std::fmt;
 use stdweb::web::{Element, EventListenerHandle, Node};
+use indexmap::set::IndexSet;
 
 pub use self::vcomp::VComp;
 pub use self::vlist::VList;
@@ -40,7 +41,7 @@ type Listeners<COMP> = Vec<Box<dyn Listener<COMP>>>;
 type Attributes = HashMap<String, String>;
 
 /// A set of classes.
-type Classes = HashSet<String>;
+type Classes = IndexSet<String>;
 
 /// Patch for DOM node modification.
 enum Patch<ID, T> {

src/virtual_dom/vtag.rs

@@ -546,7 +546,7 @@ impl<COMP: Component> PartialEq for VTag<COMP> {
             return false;
         }
 
-        if self.classes != other.classes {
+        if self.classes.iter().ne(other.classes.iter()) {
             return false;
         }
 

tests/vtag_test.rs

@@ -201,7 +201,7 @@ fn supports_multiple_classes_string() {
         <div class="class-2 class-3 class-1"></div>
     };
 
-    assert_eq!(a, b);
+    assert_ne!(a, b);
 
     if let VNode::VTag(vtag) = a {
         println!("{:?}", vtag.classes);
@@ -213,6 +213,25 @@ fn supports_multiple_classes_string() {
     }
 }
 
+#[test]
+fn keeps_order_of_classes() {
+    let a: VNode<Comp> = html! {
+        <div class="class-1 class-2   class-3",></div>
+    };
+
+    if let VNode::VTag(mut vtag) = a {
+        println!("{:?}", vtag.classes);
+        assert_eq!(
+            vtag.classes.drain(..).collect::<Vec<String>>(),
+            vec![
+                String::from("class-1"),
+                String::from("class-2"),
+                String::from("class-3")
+            ]
+        )
+    }
+}
+
 #[test]
 fn it_compares_values() {
     let a: VNode<Comp> = html! {