Update docs and tests for WITH clause

doc/clause-reference.md

@@ -297,7 +297,8 @@ order they would appear in a valid SQL statement).
 
 These provide CTE support for SQL Server. The argument to
 `:with` (or `:with-recursive`) is a sequences of pairs, each of
-a result set name (or description) and a basic SQL statement.
+a result set name (or description) and either of; a basic SQL 
+statement, a string, a keyword or a symbol.
 The result set can either be a SQL entity (a simple name)
 or a pair of a SQL entity and a set of column names.
 
@@ -310,6 +311,34 @@ user=> (sql/format '{with ((stuff {select (:*) from (foo)}),
 ["WITH stuff AS (SELECT * FROM foo), nonsense AS (SELECT * FROM bar) SELECT foo.id, bar.name FROM stuff, nonsense WHERE status = ?" 0]
 ```
 
+When the expression is a basic SQL statement in any of the pairs,
+the resulting syntax of the pair is `with ident AS expr` as shown above. 
+However, when the expression is a string, a keyword or a symbol, the resulting
+syntax of the pair is of the form `with expr AS ident` like this:
+
+```clojure
+user=> (sql/format '{with ((ts_upper_bound "2019-08-01 15:23:00"))
+                     select :*
+                     from (hits)
+                     where (= EventDate ts_upper_bound)})
+["WITH ? AS ts_upper_bound SELECT * FROM hits WHERE EventDate = ts_upper_bound" "2019-08-01 15:23:00"]
+```
+
+The syntax only varies for each pair and so you can use both SQL statements 
+and keywords/strings/symbols in the same WITH clause like this:
+
+```clojure
+user=> (sql/format '{with   ((ts_upper_bound "2019-08-01 15:23:00")
+                             (review :awesome)
+                             (stuff {select (:*) from (songs)}))
+                     select :*
+                     from   (hits, stuff)
+                     where  (and (= EventDate ts_upper_bound)
+                                 (= EventReview review))})
+["WITH ? AS ts_upper_bound, awesome AS review, stuff AS (SELECT * FROM songs) SELECT * FROM hits, stuff WHERE (EventDate = ts_upper_bound) AND (EventReview = review)"
+ "2019-08-01 15:23:00"]
+```
+
 You can specify a list of columns for the CTE like this:
 
 ```clojure

src/honey/sql.cljc

@@ -159,11 +159,6 @@
   []
   (= :sqlserver (:dialect *dialect*)))
 
-(defn- clickhouse?
-  "Helper to detect if Clickhouse is the current dialect."
-  []
-  (= :clickhouse (:dialect *dialect*)))
-
 ;; String.toUpperCase() or `str/upper-case` for that matter converts the
 ;; string to uppercase for the DEFAULT LOCALE. Normally this does what you'd
 ;; expect but things like `inner join` get converted to `İNNER JOİN` (dot over
@@ -557,20 +552,22 @@
   ;; or just entity, as far as I can tell...
   (let [[sqls params]
         (reduce-sql
-          (map
+         (map
-            (fn [[x expr :as with]]
+          (fn [[x expr :as with]]
-              (let [[sql & params]   (format-with-part x)
+            (let [[sql & params] (format-with-part x)
-                    [sql' & params'] (if (and (clickhouse?)   ;;in clickhouse the expression can be
+                  non-query-expr? (or (ident? expr) (string? expr))
-                                              (not (map? expr))) ;; a string arranged as `with expr as ident`
+                  [sql' & params'] (if non-query-expr?
-                                       (format-expr expr)
+                                     (format-expr expr)
-                                       (format-dsl expr))]
+                                     (format-dsl expr))]
+              (if non-query-expr?
+                (cond-> [(str sql' " AS " sql)]
+                        params' (into params')
+                        params  (into params))
                 ;; according to docs, CTE should _always_ be wrapped:
-                (cond-> [(if (and (clickhouse?) (not (map? expr)))
+                (cond-> [(str sql " " (as-fn with) " " (str "(" sql' ")"))]
-                           (str sql' " AS " sql)
-                           (str sql " " (as-fn with) " " (str "(" sql' ")")))]
                         params  (into params)
-                        params' (into params'))))
+                        params' (into params')))))
-            xs))]
+          xs))]
     (into [(str (sql-kw k) " " (str/join ", " sqls))] params)))
 
 (defn- format-selector [k xs]

test/honey/sql_test.cljc

@@ -144,7 +144,30 @@
                    {:values [[1 2] [4 5 6]]}]]
            :select [:*]
            :from [:static]})
-         ["WITH static (a, b, c) AS (VALUES (?, ?, NULL), (?, ?, ?)) SELECT * FROM static" 1 2 4 5 6])))
+         ["WITH static (a, b, c) AS (VALUES (?, ?, NULL), (?, ?, ?)) SELECT * FROM static" 1 2 4 5 6]))
+  (testing "When the expression passed to WITH clause is a string or `ident?` the syntax of WITH clause is `with expr AS ident`"
+    (is (= (format
+             {:with   [[:ts_upper_bound "2019-08-01 15:23:00"]]
+              :select [:*]
+              :from   [:hits]
+              :where  [:= :EventDate :ts_upper_bound]})
+           ["WITH ? AS ts_upper_bound SELECT * FROM hits WHERE EventDate = ts_upper_bound" "2019-08-01 15:23:00"]))
+    (is (= (format
+             {:with   [[:ts_upper_bound :2019-08-01]]
+              :select [:*]
+              :from   [:hits]
+              :where  [:= :EventDate :ts_upper_bound]})
+           ["WITH 2019_08_01 AS ts_upper_bound SELECT * FROM hits WHERE EventDate = ts_upper_bound"])))
+  (testing "Mixing the syntax of WITH in the resulting clause"
+    (is (= (format
+             {:with   [[:ts_upper_bound "2019-08-01 15:23:00"]
+                       [:stuff {:select [:*]
+                                :from [:songs]}]]
+              :select [:*]
+              :from   [:hits :stuff]
+              :where  [:= :EventDate :ts_upper_bound]})
+           ["WITH ? AS ts_upper_bound, stuff AS (SELECT * FROM songs) SELECT * FROM hits, stuff WHERE EventDate = ts_upper_bound"
+            "2019-08-01 15:23:00"]))))
 
 (deftest insert-into
   (is (= (format {:insert-into :foo})