Groundwork for running the real clojure.jdbc on a java.sql shim

clj-test/jdbc/core_test.clj

@@ -1,5 +1,9 @@
 (ns jdbc.core-test
-  (:require [jdbc.core :as jdbc]))
+  (:require [jdbc.core :as jdbc]
+            ;; the placeholder rewriter lives in the pg driver; requiring it here
+            ;; lets the sqlite-only run cover the lexer table. Loading db.pg does
+            ;; not need libpq present, only calling into it does.
+            [db.pg]))
 
 (def failures (atom 0))
 
@@ -87,7 +91,7 @@
   ;; really a placeholder must neither be rewritten nor consume a number. These
   ;; run without a database, so the sqlite-only build covers them.
   (println "postgres placeholder rewriting")
-  (let [rewrite (deref (resolve (symbol "jdbc.core" "pg-placeholders")))]
+  (let [rewrite (deref (resolve (symbol "db.pg" "pg-placeholders")))]
     (doseq [[label in out]
             [["no placeholders"        "select 1"                    "select 1"]
              ["bare placeholder"       "?"                           "$1"]

clj/db/jdbc.clj

@@ -0,0 +1,33 @@
+(ns db.jdbc
+  "Entry point: loads the java.sql shim, then the real clojure.jdbc on top of it,
+  then points clojure.jdbc's connection construction at the native drivers.
+
+  Require this once before using jdbc.core. Two things depend on the order. The
+  shim has to be loaded before clojure.jdbc's namespaces compile, because they
+  resolve java.sql constants at compile time. And the IConnection extension below
+  has to be loaded after clojure.jdbc's own, since the later extension is the one
+  that wins, which is how a dbspec reaches db.sqlite / db.pg instead of
+  DriverManager.
+
+      (require '[db.jdbc])
+      (require '[jdbc.core :as jdbc])
+      (with-open [conn (jdbc/connection \"sqlite::memory:\")]
+        (jdbc/fetch conn \"select 1 as one\"))
+
+  Not wired in yet. While this repo still ships its own clj/jdbc/core.clj, that
+  copy shadows the dependency on the classpath and the require below resolves to it
+  rather than to clojure.jdbc, so this namespace only does what it says once that
+  file is removed."
+  (:require [db.jdbc-shim :as shim]
+            [jdbc.proto :as proto]
+            [jdbc.core]))
+
+;; DriverManager and DataSource have nothing to load here, so a dbspec map or uri
+;; string builds a shim connection over the native driver instead. Registered after
+;; jdbc.impl's own extensions so these take precedence.
+(extend-protocol proto/IConnection
+  java.lang.String
+  (connection [s] (shim/connection s))
+
+  clojure.lang.IPersistentMap
+  (connection [m] (shim/connection m)))