feat: support while loop in rt.postgres grammar

- Registered `:while` op in `rt.postgres.grammar/+features+`.
- Added `pg-while-block` in `rt.postgres.grammar.form-let` to handle AST transformation.
- Added `block-while-block` in `rt.postgres.grammar.common` to emit PL/pgSQL `WHILE ... LOOP ... END LOOP;`.
- Added unit test in `rt.postgres.grammar.form-let-test`.

Author: google-labs-jules[bot]

src/rt/postgres/grammar.clj

@@ -88,6 +88,7 @@
 
         :letblk  {:op :letblk  :symbol #{'let:block}   :macro #'form-let/pg-tf-let-block :emit :macro :type :block}
         :let     {:op :let     :symbol #{'let}         :macro #'form-let/pg-tf-let :emit :macro :type :block}
+        :while   {:op :while   :symbol #{'while}       :emit  #'form-let/pg-while-block :type :block}
         :loop    {:op :loop    :symbol #{'loop}        :emit  #'form-let/pg-loop-block :type :block}
         :case    {:op :case    :symbol #{'case}        :emit  #'form-let/pg-case-block :type :block}
         :forech  {:op :forech  :symbol #{'for:each}    :macro #'tf/pg-tf-foreach :emit :macro :type :block}

src/rt/postgres/grammar/common.clj

@@ -315,6 +315,14 @@
      \\ (\| (~'do ~@forms))
      \\ :end-loop]))
 
+(defn block-while-block
+  "emits while block"
+  {:added "4.0"}
+  ([condition & forms]
+   `[:while ~condition :loop
+     \\ (\| (~'do ~@forms))
+     \\ :end-loop \;]))
+
 (defn block-case-block
   "emits case block"
   {:added "4.0"}

src/rt/postgres/grammar/form_let.clj

@@ -213,6 +213,16 @@
       grammar
       mopts))))
 
+(defn pg-while-block
+  "creates a while block"
+  {:added "4.0"}
+  ([[_ condition & forms] grammar mopts]
+   (binding [*input-syms* (or *input-syms* (volatile! #{}))]
+     (emit-common/*emit-fn*
+      (apply common/block-while-block condition forms)
+      grammar
+      mopts))))
+
 (defn pg-case-block
   "creates a case block"
   {:added "4.0"}

test/rt/postgres/grammar/form_let_test.clj

@@ -95,6 +95,12 @@
     (pg-loop-block '(loop [] (let [a 1] (return a))) nil nil))
   => "block")
 
+^{:refer rt.postgres.grammar.form-let/pg-while-block :added "4.0"}
+(fact "creates a while block"
+  (with-redefs [emit-common/*emit-fn* (fn [& _] "block")]
+    (pg-while-block '(while (true) (let [a 1] (return a))) nil nil))
+  => "block")
+
 ^{:refer rt.postgres.grammar.form-let/pg-case-block :added "4.0"}
 (fact "creates a case block"
   (with-redefs [emit-common/*emit-fn* (fn [& _] "block")]