refactor: remove emacsql-sqlite backend option

This option is no longer supported in emacsql 4.0 and was throwing
linter errors in CI.

Ref: 7a79c2be3d

.github/workflows/test.yml

@@ -36,7 +36,11 @@ jobs:
     strategy:
       matrix:
         emacs_version:
-          - 27.1
+          # REVIEW: we do not yet have the bootstrapping in place to test
+          #         versions of emacs without built-in sqlite (pre 29.1)
+          # - 27.2
+          # - 28.2
+          - 29.4
           - snapshot
     steps:
       - uses: purcell/setup-emacs@master

doc/org-roam.org

@@ -268,40 +268,6 @@ file:
 install-info /path/to/my/info/files/org-roam.info /path/to/my/info/files/dir
 #+end_src
 
-** Installation Troubleshooting
-*** C Compiler
-Org-roam relies on an Emacs package called ~emacsql~ and ~emacsql-sqlite~ to
-work with the ~sqlite~ database. Both of them should be installed automatically
-in your Emacs environment as a prerequisite for Org-roam when you install it.
-
-~emacsql-sqlite~ requires a C compiler (e.g. ~gcc~ or ~clang~) to be present in
-your computer. How to install a C compiler depends on the OS that you use.
-
-**** C Compiler for Windows
-
-One of the easiest ways to install a C compiler in Windows is to use [[https://www.msys2.org/][MSYS2]] as at the time of this writing:
-
-1. Download and use the installer in the official MSYS2 website
-2. Run MSYS2 and in its terminal, type the following and answer "Y" to
-   proceed -- this will install ~gcc~ in your PC:
-
-   #+BEGIN_SRC bash
-     pacman -S gcc
-   #+END_SRC
-
-4. On Windows, add ~C:\msys64\usr\bin~ (command =where gcc= in MSYS2 terminal
-   can tell you the correct path) to ~PATH~ in your environmental variables
-
-5. Launch Emacs and call ~M-x org-roam-db-autosync-mode~ (launch Emacs after
-   defining the path, so that Emacs can recognize it)
-
-This will automatically start compiling ~emacsql-sqlite~; you should see a
-message in minibuffer. It may take a while until compilation completes. Once
-complete, you should see a new file ~emacsql-sqlite.exe~ created in a subfolder
-named ~sqlite~ under ~emacsql-sqlite~ installation folder. It's typically in
-your Emacs configuration folder like this:
-~/.config/emacs/elpa/emacsql-sqlite-20190727.1710/sqlite~
-
 * Getting Started
 ** The Org-roam Node
 
@@ -459,18 +425,18 @@ can set ~org-roam-node-display-template~ as such:
 ** How to cache
 
 Org-roam uses a sqlite database to perform caching, but there are multiple Emacs
-libraries that can be used. The default used by Org-roam is ~emacs-sqlite~.
+libraries that can be used. The default used by Org-roam is
-Below the pros and cons of each package is used:
+[[https://github.com/magit/emacsql/blob/main/emacsql-sqlite-builtin.el][~emacs-sqlite-builtin~]].  Below the pros and cons of each package is used:
 
-[[https://github.com/skeeto/emacsql][**emacs-sqlite**]]
+[[https://melpa.org/#/emacsql-sqlite-builtin][**emacsql-sqlite-builtin**]]
 
-The default option used by Org-roam. This library is the most mature and
+~emacsql-sqlite-builtin~ uses the in-built SQLite support for Emacs 29 and
-well-supported and is imported by default in Org-roam.
+later. This is the default option if you are using a version of Emacs that
+supports it.
 
-One downside of using ~emacs-sqlite~ is that using it requires compilation and
+#+begin_src emacs-lisp
-can cause issues in some environments (especially Windows). If you have issues
+  (setq org-roam-database-connector 'sqlite-builtin)
-producing the customized binary required by ~emacs-sqlite~, consider using
+#+end_src
-~emacs-sqlite3~.
 
 [[https://github.com/cireu/emacsql-sqlite3][**emacs-sqlite3**]]
 
@@ -489,24 +455,12 @@ To use ~emacsql-sqlite3~, ensure that the package is installed, and set:
 [[https://melpa.org/#/emacsql-sqlite-module][**emacssql-sqlite-module**]] (previously emacsql-libsqlite3)
 
 ~emacs-sqlite-module~ is a relatively young package which uses an Emacs module that
-exposes parts of the SQLite C API to Emacs Lisp, instead of using subprocess as
+exposes parts of the SQLite C API to Emacs Lisp.
-~emacsql-sqlite~ does. It is expected to be a more performant drop-in
-replacement for ~emacs-sqlite~.
 
 #+begin_src emacs-lisp
   (setq org-roam-database-connector 'sqlite-module)
 #+end_src
 
-[[https://melpa.org/#/emacsql-sqlite-builtin][**emacsql-sqlite-builtin**]]
-
-~emacsql-sqlite-builtin~ uses the in-built SQLite support for Emacs 29 and
-later. This is the recommended option if you are using a version of Emacs that
-supports it.
-
-#+begin_src emacs-lisp
-  (setq org-roam-database-connector 'sqlite-builtin)
-#+end_src
-
 ** What to cache
 
 By default, all nodes (any headline or file with an ID) are cached by Org-roam.
@@ -1672,21 +1626,6 @@ to the publishing directory.  Example code follows:
                                          (kill-buffer (file-name-nondirectory svg))
                                          (setq my-publish-time 0)))))
 #+end_src
-** I'm seeing this "Selecting deleted buffer" error. What do I do?
-
-The "selecting deleted buffer" error usually occurs when you don't have a
-working ~emacsql-sqlite~ executable. Org-roam relies on this executable to
-function properly, and doesn't catch this error. This issue is most commonly
-seen on Windows setups. You can browse through the various GitHub issues posted
-about this [[https://github.com/org-roam/org-roam/issues?q=is%3Aissue+selecting+deleted][here]].
-
-To fix this, you can try the following:
-
-1. If on Windows, try replacing your system binary with [[https://github.com/nobiot/emacsql-sqlite.exe][this one]] that has been proven
-   to work
-2. Use the ~emacsql-sqlite3~ option rather than compiling your own emacsql
-   binary (see [[*How to cache][How to cache]]).
-
 * Developer's Guide to Org-roam
 ** Org-roam's Design Principle
 

org-roam-db.el

@@ -41,18 +41,15 @@
                                                   (functionp 'emacsql-sqlite-builtin))
                                                 (functionp 'sqlite-open))
                                            'sqlite-builtin
-                                         'sqlite)
+                                         'sqlite-module)
   "The database connector used by Org-roam.
 This must be set before `org-roam' is loaded.  To use an alternative
 connector you must install the respective package explicitly.
-The default is `sqlite', which uses the `emacsql-sqlite' library
+If you are using Emacs 29 or newer, then the default connector is
-that is being maintained in the same repository as `emacsql'
-itself.
-If you are using Emacs 29, then the recommended connector is
 `sqlite-builtin', which uses the new builtin support for SQLite.
 You need to install the `emacsql-sqlite-builtin' package to use
 this connector.
-If you are using an older Emacs release, then the recommended
+If you are using an older Emacs release, then the default
 connector is `sqlite-module', which uses the module provided by
 the `sqlite3' package.  This is very similar to the previous
 connector and the built-in support in Emacs 29 derives from this
@@ -67,7 +64,7 @@ the official `sqlite3' cli tool, which is not intended
 to be used like this.  See https://nullprogram.com/blog/2014/02/06/."
   :package-version '(forge . "0.3.0")
   :group 'org-roam
-  :type '(choice (const sqlite)
+  :type '(choice
           (const sqlite-builtin)
           (const sqlite-module)
           (const :tag "libsqlite3 (OBSOLETE)" libsqlite3)
@@ -156,7 +153,6 @@ ROAM_REFS."
   (gethash (expand-file-name (file-name-as-directory org-roam-directory))
            org-roam-db--connection))
 
-(declare-function emacsql-sqlite "ext:emacsql-sqlite")
 (declare-function emacsql-sqlite3 "ext:emacsql-sqlite3")
 (declare-function emacsql-libsqlite3 "ext:emacsql-libsqlite3")
 (declare-function emacsql-sqlite-builtin "ext:emacsql-sqlite-builtin")
@@ -165,10 +161,6 @@ ROAM_REFS."
 (defun org-roam-db--conn-fn ()
   "Return the function for creating the database connection."
   (cl-case org-roam-database-connector
-    (sqlite
-     (progn
-       (require 'emacsql-sqlite)
-       #'emacsql-sqlite))
     (sqlite-builtin
      (progn
        (require 'emacsql-sqlite-builtin)

org-roam.el

@@ -80,6 +80,7 @@
 (require 'magit-section)
 
 (require 'emacsql)
+;; emacsql-sqlite provides an interface to a chosen emacsql SQLite backend (e.g. emacs-sqlite-builtin)
 (require 'emacsql-sqlite)
 
 (require 'org)