From 2de83d48c406bdb99c2df1d57bd35afd7a6d62d8 Mon Sep 17 00:00:00 2001
From: Juho Teperi <juho.teperi@iki.fi>
Date: Fri, 1 Dec 2023 16:01:32 +0200
Subject: [PATCH 1/2] Add defc macro to create fn components with Fast Refresh
 support

---
 .clj-kondo/config.edn           |  1 +
 demo/reagentdemo/dev.cljs       | 10 ++++--
 demo/reagentdemo/intro.cljs     | 36 ++++++++++-----------
 package-lock.json               | 16 ++++++++++
 package.json                    | 13 +++++---
 src/reagent/core.clj            | 55 ++++++++++++++++++++++++++++++++-
 src/reagent/dev.clj             |  1 +
 src/reagent/dev.cljs            | 21 +++++++++++++
 src/reagent/impl/component.cljs |  5 +++
 src/reagent/impl/template.cljs  | 15 +++++++--
 10 files changed, 144 insertions(+), 29 deletions(-)
 create mode 100644 src/reagent/dev.clj
 create mode 100644 src/reagent/dev.cljs

diff --git a/.clj-kondo/config.edn b/.clj-kondo/config.edn
index 4de750ff..f30df508 100644
--- a/.clj-kondo/config.edn
+++ b/.clj-kondo/config.edn
@@ -1,4 +1,5 @@
 {:lint-as {reagent.core/with-let clojure.core/let
+           reagent.core/defc clojure.core/defn
            reagenttest.utils/deftest clojure.test/deftest}
  :linters {:unused-binding {:level :off}
            :missing-else-branch {:level :off}
diff --git a/demo/reagentdemo/dev.cljs b/demo/reagentdemo/dev.cljs
index 3ff540f9..3b470ee1 100644
--- a/demo/reagentdemo/dev.cljs
+++ b/demo/reagentdemo/dev.cljs
@@ -1,11 +1,15 @@
 (ns reagentdemo.dev
   "Initializes the demo app, and runs the tests."
-  (:require [reagentdemo.core :as core]
+  (:require [reagent.dev]
+            [reagentdemo.core :as core]
             [reagenttest.runtests :as tests]))
 
+(reagent.dev/init-fast-refresh!)
+
 (enable-console-print!)
 
 (defn ^:dev/after-load init! []
-  (core/init! (tests/init!)))
+  (js/console.log (reagent.dev/refresh!))
+  (tests/init!))
 
-(init!)
+(defonce _init (core/init!))
diff --git a/demo/reagentdemo/intro.cljs b/demo/reagentdemo/intro.cljs
index 6ed6e86b..0ce9f27f 100644
--- a/demo/reagentdemo/intro.cljs
+++ b/demo/reagentdemo/intro.cljs
@@ -6,44 +6,44 @@
             [simpleexample.core :as simple]
             [todomvc.core :as todo]))
 
-(defn simple-component []
+(r/defc simple-component []
   [:div
    [:p "I am a component!"]
    [:p.someclass
     "I have " [:strong "bold"]
     [:span {:style {:color "red"}} " and red "] "text."]])
 
-(defn simple-parent []
+(r/defc simple-parent []
   [:div
    [:p "I include simple-component."]
    [simple-component]])
 
-(defn hello-component [name]
+(r/defc hello-component [name]
   [:p "Hello, " name "!"])
 
-(defn say-hello []
+(r/defc say-hello []
   [hello-component "world"])
 
-(defn lister [items]
+(r/defc lister [items]
   [:ul
    (for [item items]
      ^{:key item} [:li "Item " item])])
 
-(defn lister-user []
+(r/defc lister-user []
   [:div
    "Here is a list:"
    [lister (range 3)]])
 
 (def click-count (r/atom 0))
 
-(defn counting-component []
+(r/defc counting-component []
   [:div
    "The atom " [:code "click-count"] " has value: "
    @click-count ". "
    [:input {:type "button" :value "Click me!"
             :on-click #(swap! click-count inc)}]])
 
-(defn atom-input [value]
+(r/defc atom-input [value]
   [:input {:type "text"
            :value @value
            :on-change #(reset! value (-> % .-target .-value))}])
@@ -62,7 +62,7 @@
       [:div
        "Seconds Elapsed: " @seconds-elapsed])))
 
-(defn render-simple []
+(r/defc render-simple []
   (rdom/render
     [simple-component]
     (.-body js/document)))
@@ -75,7 +75,7 @@
 
 (def bmi-data (r/atom (calc-bmi {:height 180 :weight 80})))
 
-(defn slider [param value min max invalidates]
+(r/defc slider [param value min max invalidates]
   [:input {:type "range" :value value :min min :max max
            :style {:width "100%"}
            :on-change (fn [e]
@@ -87,7 +87,7 @@
                                      (dissoc invalidates)
                                      calc-bmi)))))}])
 
-(defn bmi-component []
+(r/defc bmi-component []
   (let [{:keys [weight height bmi]} @bmi-data
         [color diagnose] (cond
                           (< bmi 18.5) ["orange" "underweight"]
@@ -114,7 +114,7 @@
 (def ns-src-with-rdom (s/syntaxed "(ns example
   (:require [reagent.dom :as rdom]))"))
 
-(defn intro []
+(r/defc intro []
   (let [github {:href "https://github.com/reagent-project/reagent"}
         clojurescript {:href "https://github.com/clojure/clojurescript"}
         react {:href "https://reactjs.org/"}
@@ -176,7 +176,7 @@
      is a map). See React’s " [:a react-keys "documentation"] "
      for more info."]]))
 
-(defn managing-state []
+(r/defc managing-state []
   [:div.demo-text
    [:h2 "Managing state in Reagent"]
 
@@ -224,7 +224,7 @@
    component is updated when your data changes. Reagent assumes by
    default that two objects are equal if they are the same object."]])
 
-(defn essential-api []
+(r/defc essential-api []
   [:div.demo-text
    [:h2 "Essential API"]
 
@@ -240,7 +240,7 @@
                           ns-src-with-rdom
                           (s/src-of [:simple-component :render-simple])]}]])
 
-(defn performance []
+(r/defc performance []
   [:div.demo-text
    [:h2 "Performance"]
 
@@ -285,7 +285,7 @@
    into the browser, React automatically attaches event-handlers to
    the already present DOM tree."]])
 
-(defn bmi-demo []
+(r/defc bmi-demo []
   [:div.demo-text
    [:h2 "Putting it all together"]
 
@@ -301,7 +301,7 @@
                           (s/src-of [:calc-bmi :bmi-data :slider
                                      :bmi-component])]}]])
 
-(defn complete-simple-demo []
+(r/defc complete-simple-demo []
   [:div.demo-text
    [:h2 "Complete demo"]
 
@@ -313,7 +313,7 @@
                     :complete true
                     :src (s/src-of nil "simpleexample/core.cljs")}]])
 
-(defn todomvc-demo []
+(r/defc todomvc-demo []
   [:div.demo-text
    [:h2 "Todomvc"]
 
diff --git a/package-lock.json b/package-lock.json
index 6cc407e9..b692552c 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -19,6 +19,7 @@
         "prop-types": "15.8.1",
         "react": "18.2.0",
         "react-dom": "18.2.0",
+        "react-refresh": "^0.14.0",
         "shadow-cljs": "2.20.7",
         "webpack": "5.65.0",
         "webpack-cli": "4.9.1"
@@ -3491,6 +3492,15 @@
       "integrity": "sha512-24e6ynE2H+OKt4kqsOvNd8kBpV65zoxbA4BVsEOB3ARVWQki/DHzaUoC5KuON/BiccDaCCTZBuOcfZs70kR8bQ==",
       "dev": true
     },
+    "node_modules/react-refresh": {
+      "version": "0.14.0",
+      "resolved": "https://registry.npmjs.org/react-refresh/-/react-refresh-0.14.0.tgz",
+      "integrity": "sha512-wViHqhAd8OHeLS/IRMJjTSDHF3U9eWi62F/MledQGPdJGDhodXJ9PBLNGr6WWL7qlH12Mt3TyTpbS+hGXMjCzQ==",
+      "dev": true,
+      "engines": {
+        "node": ">=0.10.0"
+      }
+    },
     "node_modules/readable-stream": {
       "version": "2.3.5",
       "resolved": "https://registry.npmjs.org/readable-stream/-/readable-stream-2.3.5.tgz",
@@ -7630,6 +7640,12 @@
       "integrity": "sha512-24e6ynE2H+OKt4kqsOvNd8kBpV65zoxbA4BVsEOB3ARVWQki/DHzaUoC5KuON/BiccDaCCTZBuOcfZs70kR8bQ==",
       "dev": true
     },
+    "react-refresh": {
+      "version": "0.14.0",
+      "resolved": "https://registry.npmjs.org/react-refresh/-/react-refresh-0.14.0.tgz",
+      "integrity": "sha512-wViHqhAd8OHeLS/IRMJjTSDHF3U9eWi62F/MledQGPdJGDhodXJ9PBLNGr6WWL7qlH12Mt3TyTpbS+hGXMjCzQ==",
+      "dev": true
+    },
     "readable-stream": {
       "version": "2.3.5",
       "resolved": "https://registry.npmjs.org/readable-stream/-/readable-stream-2.3.5.tgz",
diff --git a/package.json b/package.json
index ada234f1..313dceb1 100644
--- a/package.json
+++ b/package.json
@@ -1,7 +1,6 @@
 {
   "name": "@reagent-project/reagent",
   "private": true,
-  "dependencies": {},
   "scripts": {
     "start": "lein figwheel client-npm"
   },
@@ -16,11 +15,15 @@
     "karma-sourcemap-loader": "0.3.8",
     "karma-webpack": "5.0.0",
     "md5-file": "5.0.0",
-    "shadow-cljs": "2.20.7",
-    "webpack": "5.65.0",
-    "webpack-cli": "4.9.1",
     "prop-types": "15.8.1",
     "react": "18.2.0",
-    "react-dom": "18.2.0"
+    "react-dom": "18.2.0",
+    "react-refresh": "^0.14.0",
+    "shadow-cljs": "2.20.7",
+    "webpack": "5.65.0",
+    "webpack-cli": "4.9.1"
+  },
+  "volta": {
+    "node": "18.15.0"
   }
 }
diff --git a/src/reagent/core.clj b/src/reagent/core.clj
index d2abe46e..35439bae 100644
--- a/src/reagent/core.clj
+++ b/src/reagent/core.clj
@@ -1,5 +1,6 @@
 (ns reagent.core
-  (:require [reagent.ratom :as ra]))
+  (:require [cljs.core :as core]
+            [reagent.ratom :as ra]))
 
 (defmacro with-let
   "Bind variables as with let, except that when used in a component
@@ -24,3 +25,55 @@
   [& body]
   `(reagent.ratom/make-reaction
     (fn [] ~@body)))
+
+;; From uix.lib
+(defn parse-sig [name fdecl]
+  (let [[fdecl m] (if (string? (first fdecl))
+                    [(next fdecl) {:doc (first fdecl)}]
+                    [fdecl {}])
+        [fdecl m] (if (map? (first fdecl))
+                    [(next fdecl) (conj m (first fdecl))]
+                    [fdecl m])
+        fdecl (if (vector? (first fdecl))
+                (list fdecl)
+                fdecl)
+        [fdecl m] (if (map? (last fdecl))
+                    [(butlast fdecl) (conj m (last fdecl))]
+                    [fdecl m])
+        m (conj {:arglists (list 'quote (#'cljs.core/sigs fdecl))} m)
+        m (conj (if (meta name) (meta name) {}) m)]
+    [(with-meta name m) fdecl]))
+
+(defmacro defc
+  "Creates function component"
+  [sym & fdecl]
+  ;; Just use original fdecl always for render fn.
+  ;; Parse for fname metadata.
+  (let [[fname fdecl] (parse-sig sym fdecl)
+        ;; FIXME: Should probably support multiple arities for components
+        [args & fdecl] (first fdecl)
+        var-sym (-> (str (-> &env :ns :name) "/" sym) symbol (with-meta {:tag 'js}))]
+    `(do
+       (def ~fname (reagent.impl.component/memo
+                     (fn ~fname [jsprops#]
+                       ;; FIXME: Replace functional-render with new function that takes renderFn as parameter.
+                       ;; Need completely new component impl for that.
+                       (let [render-fn# (fn ~'reagentRender ~args
+                                          (when ^boolean goog.DEBUG
+                                            (when-let [sig-f# (.-fast-refresh-signature ~var-sym)]
+                                              (sig-f#)))
+                                          ~@fdecl)
+                             jsprops2# (js/Object.assign (core/js-obj "reagentRender" render-fn#) jsprops#)]
+                         (reagent.impl.component/functional-render reagent.impl.template/*current-default-compiler* jsprops2#)))))
+       (reagent.dev/register ~var-sym ~(str fname))
+       (when ^boolean goog.DEBUG
+         (let [sig# (reagent.dev/signature)]
+           ;; Empty signature but set forceReset flag.
+           (sig# ~var-sym "" true nil)
+           (set! (.-fast-refresh-signature ~var-sym) sig#)))
+       (set! (.-reagent-component ~fname) true)
+       (set! (.-displayName ~fname) ~(str sym)))))
+
+(comment
+  (clojure.pprint/pprint (macroexpand-1 '(defc foobar [a b] (+ a b))))
+  (clojure.pprint/pprint (clojure.walk/macroexpand-all '(defc foobar [a b] (+ a b)))))
diff --git a/src/reagent/dev.clj b/src/reagent/dev.clj
new file mode 100644
index 00000000..f6fda86c
--- /dev/null
+++ b/src/reagent/dev.clj
@@ -0,0 +1 @@
+(ns reagent.dev)
diff --git a/src/reagent/dev.cljs b/src/reagent/dev.cljs
new file mode 100644
index 00000000..a14fbbe6
--- /dev/null
+++ b/src/reagent/dev.cljs
@@ -0,0 +1,21 @@
+(ns reagent.dev
+  (:require ["react-refresh/runtime" :as refresh])
+  (:require-macros [reagent.dev]))
+
+(defn signature []
+  (refresh/createSignatureFunctionForTransform))
+
+(defn register [type id]
+  (refresh/register type id))
+
+;;;; Public API ;;;;
+
+(defn init-fast-refresh!
+  "Injects react-refresh runtime. Should be called before UI is rendered"
+  []
+  (refresh/injectIntoGlobalHook js/window))
+
+(defn refresh!
+  "Should be called after hot-reload, in shadow's ^:dev/after-load hook"
+  []
+  (refresh/performReactRefresh))
diff --git a/src/reagent/impl/component.cljs b/src/reagent/impl/component.cljs
index 3304b9e6..e355fec2 100644
--- a/src/reagent/impl/component.cljs
+++ b/src/reagent/impl/component.cljs
@@ -477,3 +477,8 @@
             f (react/memo f functional-render-memo-fn)]
         (cache-react-class compiler tag f)
         f)))
+
+;; defc impl
+
+(defn memo [f]
+  (react/memo f functional-render-memo-fn))
diff --git a/src/reagent/impl/template.cljs b/src/reagent/impl/template.cljs
index c8300b78..8389c399 100644
--- a/src/reagent/impl/template.cljs
+++ b/src/reagent/impl/template.cljs
@@ -26,8 +26,9 @@
   (or (named? x)
       (string? x)))
 
-(defn ^boolean valid-tag? [x]
+(defn ^boolean valid-tag? [^clj x]
   (or (hiccup-tag? x)
+      (.-reagent-component x)
       (ifn? x)
       (instance? NativeWrapper x)))
 
@@ -162,6 +163,13 @@
       (set! (.-key jsprops) key))
     (react/createElement c jsprops)))
 
+(defn reag-element-2 [tag v]
+  (let [jsprops #js {}]
+    (set! (.-argv jsprops) (subvec v 1))
+    (when-some [key (util/react-key-from-vec v)]
+      (set! (.-key jsprops) key))
+    (react/createElement tag jsprops)))
+
 (defn function-element [tag v first-arg compiler]
   (let [jsprops #js {}]
     (set! (.-reagentRender jsprops) tag)
@@ -276,7 +284,7 @@
   (when (nil? compiler)
     (js/console.error "vec-to-elem" (pr-str v)))
   (assert (pos? (count v)) (util/hiccup-err v (comp/comp-name) "Hiccup form should not be empty"))
-  (let [tag (nth v 0 nil)]
+  (let [^clj tag (nth v 0 nil)]
     (assert (valid-tag? tag) (util/hiccup-err v (comp/comp-name) "Invalid Hiccup form"))
     (case tag
       :> (native-element (->HiccupTag (nth v 1 nil) nil nil nil) v 2 compiler)
@@ -284,6 +292,9 @@
       :f> (function-element (nth v 1 nil) v 2 compiler)
       :<> (fragment-element v compiler)
       (cond
+       (.-reagent-component tag)
+       (reag-element-2 tag v)
+
        (hiccup-tag? tag)
        (hiccup-element v compiler)
 

From 6307cc3ee646e917ced202a45a22c158f606cb52 Mon Sep 17 00:00:00 2001
From: Juho Teperi <juho.teperi@iki.fi>
Date: Fri, 1 Dec 2023 16:10:33 +0200
Subject: [PATCH 2/2] Docs

---
 doc/ReactRefresh.md | 8 ++++++++
 1 file changed, 8 insertions(+)
 create mode 100644 doc/ReactRefresh.md

diff --git a/doc/ReactRefresh.md b/doc/ReactRefresh.md
new file mode 100644
index 00000000..a4206c09
--- /dev/null
+++ b/doc/ReactRefresh.md
@@ -0,0 +1,8 @@
+# React Refresh
+
+- `reagent.dev` ns must be required before anything that loads `react-dom`
+- Don't call `r.dom/render` after reload (e.g. shadow-cljs hook)
+- Call `reagent.dev/refresh!` instead
+- Only components defined using `r/defc` will refresh
+- Reagent doesn't try to create Hook signatures for components,
+  so hook state is reset for updated components.