Optionally prefix rows with a header of the column names

Closes #36.

emacsql-sqlite-builtin.el

@@ -60,14 +60,18 @@ buffer. This is for debugging purposes."
 (cl-defmethod emacsql-send-message
   ((connection emacsql-sqlite-builtin-connection) message)
   (condition-case err
-      (mapcar (lambda (row)
-                (mapcar (lambda (col)
-                          (cond ((null col) nil)
-                                ((equal col "") "")
-                                ((numberp col) col)
-                                (t (read col))))
-                        row))
-              (sqlite-select (oref connection handle) message nil nil))
+      (let ((include-header emacsql-include-header))
+        (mapcar (lambda (row)
+                  (prog1 (mapcar (lambda (col)
+                                   (cond (include-header col)
+                                         ((null col) nil)
+                                         ((equal col "") "")
+                                         ((numberp col) col)
+                                         (t (read col))))
+                                 row)
+                    (setq include-header nil)))
+                (sqlite-select (oref connection handle) message nil
+                               (and emacsql-include-header 'full))))
     ((sqlite-error sqlite-locked-error)
      (if (stringp (cdr err))
          (signal 'emacsql-error (list (cdr err)))

emacsql-sqlite-common.el

@@ -83,6 +83,12 @@ Also see http://www.sqlite.org/lang_keywords.html.")
 Elements have the form (ERRCODE SYMBOLIC-NAME EMACSQL-ERROR
 ERRSTR).  Also see https://www.sqlite.org/rescode.html.")
 
+(defconst emacsql-include-header nil
+  "Whether to include names of columns as an additional row.
+Never enable this globally, only let-bind it around calls to `emacsql'.
+Currently only supported by `emacsql-sqlite-builtin-connection' and
+`emacsql-sqlite-module-connection'.")
+
 ;;; Utilities
 
 (defun emacsql-sqlite-open (file &optional debug)

emacsql-sqlite-module.el

@@ -64,10 +64,14 @@ buffer. This is for debugging purposes."
 (cl-defmethod emacsql-send-message
   ((connection emacsql-sqlite-module-connection) message)
   (condition-case err
-      (let (rows)
+      (let ((include-header emacsql-include-header)
+            (rows ()))
         (sqlite3-exec (oref connection handle)
                       message
-                      (lambda (_ row __)
+                      (lambda (_ row header)
+                        (when include-header
+                          (push header rows)
+                          (setq include-header nil))
                         (push (mapcar (lambda (col)
                                         (cond ((null col) nil)
                                               ((equal col "") "")