Fix #586: extend protocol to nil (#587)

squint-cljs · Nov 29, 2024 · bdb7ddc · bdb7ddc
1 parent 57f0301
commit bdb7ddc
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 [Squint](https://github.com/squint-cljs/squint): Light-weight ClojureScript dialect
 
+## v0.8.126 (2024-11-29)
+
+- [#586](https://github.com/squint-cljs/squint/issues/586): support extending protocol to `nil`
+
 ## v0.8.125 (2024-11-28)
 
 - [#581](https://github.com/squint-cljs/squint/issues/581): support docstring in `defprotocol`

diff --git a/resources/squint/core.edn b/resources/squint/core.edn
@@ -14,6 +14,7 @@
   _LT__EQ_
   _PLUS_
   _STAR_
+  __protocol_satisfies
   _iterator
   abs
   aclone

diff --git a/src/squint/core.js b/src/squint/core.js
@@ -60,7 +60,12 @@ export function _(...xs) {
   return xs.reduce((x, y) => x - y);
 }
 
+export const __protocol_satisfies = {};
+
 export function satisfies_QMARK_(protocol, x) {
+  if (x == null) {
+    return __protocol_satisfies[protocol];
+  }
   return x[protocol];
 }
 

diff --git a/src/squint/internal/protocols.cljc b/src/squint/internal/protocols.cljc
@@ -2,10 +2,13 @@
   (:require [clojure.core :as core]))
 
 (core/defn- emit-protocol-method-arity
-  [method-sym args]
-  `(~args
-    ((unchecked-get ~(first args) ; this
-                    ~method-sym) ~@args)))
+  [mname method-sym args]
+  (let [this (first args)]
+    `(~args
+      (if (nil? ~this)
+        ((unchecked-get ~mname nil)  ~@args)
+        ((unchecked-get ~(first args) ;; this
+                        ~method-sym) ~@args)))))
 
 (core/defn- emit-protocol-method
   [p method]
@@ -19,7 +22,7 @@
         (js/Symbol ~(str p "_" mname)))
       (defn ~mname
         ~@(when mdocs [mdocs])
-        ~@(map #(emit-protocol-method-arity method-sym %) margs)))))
+        ~@(map #(emit-protocol-method-arity mname method-sym %) margs)))))
 
 (core/defn core-defprotocol
   [_&env _&form p & doc+methods]
@@ -56,7 +59,8 @@
 (defn insert-this [method-bodies]
   (if (vector? (first method-bodies))
     (list* (first method-bodies)
-           (list 'js* "const self__ = this")
+           (with-meta (list 'js* "const self__ = this;")
+             {:context :statement})
            (rest method-bodies))
     ;; multi-arity
     (map insert-this method-bodies)))
@@ -68,16 +72,26 @@
                (str mname)
                (symbol (str psym "_" mname)))
         f `(fn ~@(insert-this (rest method)))]
-    `(let [f# ~f]
-       (unchecked-set
-        (.-prototype ~type-sym) ~msym f#))))
+    (if (nil? type-sym)
+      `(let [f# ~f]
+         (unchecked-set
+          ~mname
+          ~type-sym f#))
+      `(let [f# ~f]
+         (unchecked-set
+          (.-prototype ~type-sym) ~msym f#)))))
 
 (core/defn- emit-type-methods
   [type-sym [psym pmethods]]
-  `((unchecked-set
-      (.-prototype ~type-sym)
-      ~psym true)
-     ~@(map #(emit-type-method psym type-sym %) pmethods)))
+  (let [flag (if (nil? type-sym)
+               `(unchecked-set
+                 ~'clojure.core/__protocol_satisfies
+                 ~psym true)
+               `(unchecked-set
+                 (.-prototype ~type-sym)
+                 ~psym true))]
+    `(~flag
+      ~@(map #(emit-type-method psym type-sym %) pmethods))))
 
 (core/defn core-extend-type
   [_&env _&form type-sym & impls]

diff --git a/test/squint/compiler_test.cljs b/test/squint/compiler_test.cljs
@@ -458,6 +458,22 @@
                                       object (i [s] s))
                      [(i "dude") (i 1)])))))
 
+(deftest defprotocol-extend-protocol-empty-body-test
+  (is (eq nil
+          (jsv! '(do (defprotocol Identity (i [this]))
+                     (extend-protocol Identity string (i [s]))
+                     (i "dude"))))))
+
+(deftest defprotocol-extend-protocol-nil
+  (is (eq ["nil" "boolean" "string" true]
+          (jsv! '(do (defprotocol Identity (i [this]))
+                     (extend-protocol Identity nil (i [s] "nil"))
+                     (extend-protocol Identity boolean (i [s] "boolean"))
+                     (extend-protocol Identity string (i [s] "string"))
+                     [(i nil) (i false) (i "")
+                      (satisfies? Identity nil)
+                      ])))))
+
 (deftest deftype-test
   (is (= 1 (jsv! '(do (deftype Foo [x]) (.-x (->Foo 1))))))
   (is (eq [:foo :bar]