[nongnu] elpa/emacsql 76bf0c34dc 038/427: Add rudimentary :where expander.

[ELPA Syncer]

branch: elpa/emacsql
commit 76bf0c34dce3efb24702635a341b51b7f2e754ef
Author: Christopher Wellons <wellons@nullprogram.com>
Commit: Christopher Wellons <wellons@nullprogram.com>

    Add rudimentary :where expander.
---
 README.md  |  5 ++---
 emacsql.el | 15 +++++++++++++++
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/README.md b/README.md
index f288c265ee..f323cf7f88 100644
--- a/README.md
+++ b/README.md
@@ -28,9 +28,8 @@ Requires Emacs 24 or later.
 (emacsql-insert db 'employees ["Jeff"  1000 60000.0]
                               ["Susan" 1001 64000.0])
 
-;; The high-level SELECT interface is a work in progress.
-(emacsql-select-raw db (concat "SELECT name, id FROM employees "
-                               "WHERE salary > 60000;"))
+;; Query the database for results:
+(emacsql db [:select [name id] :from employees :where (> salary 60000)])
 ;; => (("Susan" 1001))
 ```
 
diff --git a/emacsql.el b/emacsql.el
index ebb62d31b8..ef6a7a0188 100644
--- a/emacsql.el
+++ b/emacsql.el
@@ -386,6 +386,21 @@ KIND should be :value or :identifier."
       (list "FROM %s" (cons (emacsql-var table) :identifier))
     (list (concat "FROM " (emacsql-escape-format table :identifier)))))
 
+(emacsql-defexpander :where (expr)
+  (let ((vars ()))
+    (cl-flet* ((collect (thing kind)
+                 (push (cons (emacsql-var thing) kind) vars) "%s")
+               (handle (v)
+                 (cond ((emacsql-var v) (collect v))
+                       ((symbolp v) (emacsql-escape-format v :identifier))
+                       ((emacsql-escape-value v)))))
+      (cl-destructuring-bind (op a b) expr
+        (cons (format "WHERE %s %s %s"
+                      (handle a)
+                      op
+                      (handle b))
+              vars)))))
+
 (provide 'emacsql)
 
 ;;; emacsql.el ends here