SuperBOL mode for GNU/Emacs

We provide an extension of the cobol-mode.el of ELPA under the name cobol-superbol-mode.el that provides some fixes and run with our LSP server for COBOL.

Standard file `cobol-superbol-mode.el`

We provide cobol-superbol-mode.el as a fork of cobol-mode.el from ELPA, with a few fixes:

Better indentation
Minor modes to switch between formats
Documentation accessible from the COBOL menu

Installation

If you are already using the Cobol mode by ELPA, you need to desinstall it. For that, use M-x list-packages, go to cobol-mode, type D to select it for deletion, and then x to execute the removal.

Copy the file cobol-superbol-mode.el to your $HOME/.emacs.d/lisp/ directory:

wget https://github.com/OCamlPro/superbol-studio-oss/raw/master/emacs/cobol-superbol-mode.el
wget https://github.com/OCamlPro/superbol-studio-oss/raw/master/emacs/cobol-superbol-indent.el
mkdir -p $HOME/.emacs.d/lisp/
mv cobol-superbol-*.el $HOME/.emacs.d/lisp/

and add the following lines to your $HOME/.emacs file:

(add-to-list 'load-path "~/.emacs.d/lisp/")
(autoload 'cobol-superbol-mode "cobol-superbol-mode")
(setq cobol-tab-width 3)
(setq auto-mode-alist
  (append
   '(("\\.cob\\'" . cobol-superbol-mode)
     ("\\.cbl\\'" . cobol-superbol-mode)
     ("\\.cpy\\'" . cobol-superbol-mode))
   auto-mode-alist))
(require 'cobol-superbol-indent.el)

Start a new Emacs process and open a COBOL file: verify that the COBOL menu is available and contains a SuperBOL by OCamlPro entry. You are done!

This configuration will set tabulations to be 3 spaces and free source format. If you want to change the source format, you will need to change this option using M-x customize, save and then restart emacs.

Features

The cobol-superbol-mode.el provides the following features:

colorization
indentation
comments
rulers
minor-modes for source formats
a COBOL menu with:
- an “Insert” item with a few constructions
- a sub-menu with links to GnuCOBOL documentation
- a sub-menu to switch between source formats

Customization

cobol-skeleton-alist (check the cobol–def-skeleton function)

We advise to also use the auto-complete mode also. This mode will propose completions while typing keywords (use TAB or RET to complete).

Superbol-mode with LSP

The new Superbol-mode provides an IDE that makes use of the SuperBOL LSP to provide advanced navigation and editing facilities for COBOL projects. It can be used in combination with any of the two main LSP clients that exist within the GNU/Emacs ecosystem to interact with LSP servers: lsp-mode and eglot.

Superbol-mode with lsp-mode

lsp-mode appears to be the most prominent at the moment. This client benefits from a large user-base, but is also considered “bloated” by some.

The main advantages for using it in our context is its support for semantic tokens, that provide a way for LSPs to issue information about the semantics of symbols from the source code. Compared to traditional regexp-based highlighting, semantic tokens-based highlighting can drastically improve code readability of various source code elements based on their syntactic location;

Superbol-mode with eglot

Another possibility is to use eglot, that is sometimes considered easier to configure and more lightweight than lsp-mode (which notably makes it more reactive to user inputs). Being more recent, it lacks some of the features of lsp-mode, among which is the support for semantic tokens 1. However, additionally enabling the aforementioned cobol-mode.el provides reasonable syntax highlighting.

Setup

Let us first define an environment variable that indicates where the superbol-free executable can be found. Additionally, define a variable that points to the root of the source directory for the extension:

export SUPERBOL_DIR="<directory where superbol-free can be found>";
export SUPERBOL_STUDIO_OSS_DIR="$PWD";

After this, the following command launches a GNU/Emacs instance with an lsp-mode-based client configured for COBOL files:

emacs -L "$SUPERBOL_STUDIO_OSS_DIR/emacs" \
      --load lsp-superbol \
      --eval "(custom-set-variables '(lsp-superbol-path \"$SUPERBOL_DIR\"))" \
      --funcall superbol-mode-enable-for-default-extensions

To use eglot, type the following instead:

emacs -L "$SUPERBOL_STUDIO_OSS_DIR/emacs" \
      --load eglot-superbol \
      --eval "(add-to-list 'exec-path \"$SUPERBOL_DIR\")" \
      --funcall superbol-mode-enable-for-default-extensions

Further configuration for auto-indentation:

lsp-mode provides a lsp-format-region function that may be used to use the LSP-provided intentation. When using eglot, the same functionality is provided by eglot-format.

1: Note there is a pending issue on this point at https://github.com/joaotavora/eglot/issues/615 .

Known Issues

void-function -compose: install the dash package on ELPA
Install yasnippet ?