From f778419cb9b8e21d4d16d01269da92831d007002 Mon Sep 17 00:00:00 2001
From: Chris Targett <chris@xlevus.net>
Date: Tue, 15 May 2018 21:22:32 +0100
Subject: [PATCH] Refactored parameterizer to use mutimethods

It was briefly mentioned in #honeysql on clojurians.slack.com that this
mechanism of extension uses a register method and an atom to support
extension when multimethods are used elsewhere.
---
 src/honeysql/format.cljc       | 32 ++++++++++++++------------------
 test/honeysql/format_test.cljc |  7 ++++---
 2 files changed, 18 insertions(+), 21 deletions(-)

diff --git a/src/honeysql/format.cljc b/src/honeysql/format.cljc
index 5b20861..12d201b 100644
--- a/src/honeysql/format.cljc
+++ b/src/honeysql/format.cljc
@@ -51,22 +51,18 @@
    :sqlserver #(str \[ (string/replace % "]" "]]") \])
    :oracle #(str \" (string/replace % "\"" "\"\"") \")})
 
-(def ^:private parameterizers
-  (atom
-   {:postgresql #(str "$" (swap! *all-param-counter* inc))
-   :jdbc (constantly "?")
-   :none #(str (last @*params*))}))
 
-(defn register-parameterizer
-  "Register f as a customized parameterizer.
-   E.g.:
-   (register-parameterizer :single-quote #(str \"'\" % \"'\"))
-   (format sql-map :parameterizer :single-quote)"
-  [k f]
-  (swap!
-   parameterizers
-   (fn [m]
-     (assoc m k #(f (last @*params*))))))
+(defmulti parameterize (fn [parameterizer & args] parameterizer))
+
+(defmethod parameterize :postgresql [_ value pname]
+  (str "$" (swap! *all-param-counter* inc)))
+
+(defmethod parameterize :jdbc [_ value pname]
+  "?")
+
+(defmethod parameterize :none [_ value pname]
+  (str (last @*params*)))
+
 
 (def ^:dynamic *quote-identifier-fn* nil)
 (def ^:dynamic *parameterizer* nil)
@@ -266,7 +262,7 @@
               *param-names* (atom [])
               *input-params* (atom params)
               *quote-identifier-fn* (quote-fns (:quoting opts))
-              *parameterizer* (@parameterizers (or (:parameterizer opts) :jdbc))
+              *parameterizer* (or (:parameterizer opts) :jdbc)
               *allow-dashed-names?* (:allow-dashed-names? opts)]
       (let [sql-str (to-sql sql-map)]
         (if (and (seq @*params*) (not= :none (:parameterizer opts)))
@@ -284,7 +280,7 @@
 (defn to-params-default [value pname]
   (swap! *params* conj value)
   (swap! *param-names* conj pname)
-  (*parameterizer*))
+  (parameterize *parameterizer* value pname))
 
 (extend-protocol Parameterizable
   #?@(:clj
@@ -300,7 +296,7 @@
   (to-params [value pname]
     (swap! *params* conj value)
     (swap! *param-names* conj pname)
-    (*parameterizer*))
+    (parameterize *parameterizer* value pname))
   #?(:clj Object :cljs default)
   (to-params [value pname]
     #?(:clj
diff --git a/test/honeysql/format_test.cljc b/test/honeysql/format_test.cljc
index 8d315eb..1dce993 100644
--- a/test/honeysql/format_test.cljc
+++ b/test/honeysql/format_test.cljc
@@ -5,7 +5,7 @@
             [honeysql.types :as sql]
             [honeysql.format :refer
              [*allow-dashed-names?* quote-identifier format-clause format
-              register-parameterizer]]))
+              parameterize]]))
 
 (deftest test-quote
   (are
@@ -176,8 +176,9 @@
                    :parameterizer :postgresql)
            ["WHERE (foo = $1 AND bar = $2)" "foo" "bar"]))))
 
-(register-parameterizer :single-quote #(str \' % \'))
-(register-parameterizer :mysql-fill (constantly "?"))
+
+(defmethod parameterize :single-quote [_ value pname] (str \' value \'))
+(defmethod parameterize :mysql-fill [_ value pname] "?")
 
 (deftest customized-parameterizer
   (testing "should fill param with single quote"