ob-sqlite: Use a transient in-memory database by default

* etc/ORG-NEWS (New features): Add a news entry.
* lisp/ob-sqlite.el (org-babel-execute:sqlite): Default ':db' to
":memory:" instead of throwing an error.
* testing/lisp/test-ob-sqlite.el (ob-sqlite/in-file): Test the old behavior.
* testing/lisp/test-ob-sqlite.el (ob-sqlite/in-memory): Test the new behavior.

etc/ORG-NEWS

@@ -492,6 +492,14 @@ Final hooks are added to the following commands:
 
 The prefix arguments are passed to ~org-insert-todo-heading~.
 
+*** Make ~ob-sqlite~ use in-memory databases by default
+
+~sqlite~ source blocks with no ~:db~ header argument now make SQLite
+use a temporary in-memory database instead of throwing an error,
+matching the behavior of the official ~sqlite3~ shell.  As a result,
+~sqlite~ source blocks are now usable out of the box, that is with no
+header arguments.
+
 *** Add support for ~logind~ idle time in ~org-user-idle-seconds~
 
 When Emacs is built with =dbus= support and

lisp/ob-sqlite.el

@@ -74,7 +74,6 @@ This function is called by `org-babel-execute-src-block'."
 			   (lambda (arg) (car (assq arg params)))
 			   (list :header :echo :bail :column
 				 :csv :html :line :list)))))
-    (unless db (error "ob-sqlite: can't evaluate without a database"))
     (with-temp-buffer
       (insert
        (org-babel-eval
@@ -97,7 +96,7 @@ This function is called by `org-babel-execute-src-block'."
 			      (member :html others) separator)
 			  ""
 			"-csv"))
-	  (cons "db " db)))
+          (cons "db" (or db ""))))
 	;; body of the code block
 	(org-babel-expand-body:sqlite body params)))
       (org-babel-result-cond result-params

testing/lisp/test-ob-sqlite.el

@@ -39,8 +39,40 @@
   .import $tb TestTable
   select * from TestTable;
 #+end_src"
-	    (org-babel-next-src-block)
-	    (org-babel-execute-src-block)))))
+	   (org-babel-next-src-block)
+	   (org-babel-execute-src-block)))))
+
+(ert-deftest ob-sqlite/in-memory ()
+  "Test in-memory temporariness."
+  (should
+   (equal 0
+          (progn
+            (org-test-with-temp-text
+	     "#+BEGIN_SRC sqlite
+PRAGMA user_version = 1;
+#+END_SRC"
+	     (org-babel-execute-src-block))
+            (org-test-with-temp-text
+	     "#+BEGIN_SRC sqlite
+PRAGMA user_version;
+#+END_SRC"
+	     (org-babel-execute-src-block))))))
+
+(ert-deftest ob-sqlite/in-file ()
+  "Test in-file permanency."
+  (should
+   (equal 1
+          (let ((file (org-babel-temp-file "test" ".sqlite")))
+            (org-test-with-temp-text
+	     (format "#+BEGIN_SRC sqlite :db %s
+PRAGMA user_version = 1;
+#+END_SRC" file)
+	     (org-babel-execute-src-block))
+            (org-test-with-temp-text
+	     (format "#+BEGIN_SRC sqlite :db %s
+PRAGMA user_version;
+#+END_SRC" file)
+	     (org-babel-execute-src-block))))))
 
 (provide 'test-ob-sqlite)
 ;;; test-ob-sqlite.el ends here