Feat/lexical binding

[joshbax189]

Summary

Fixes #36
Enables lexical binding, removes uses of dynamic binding and fixes some issues arising from those changes.

Major changes

• js-comint-repl (cmd) signature change to js-comint-repl (&optional cmd),
  This better reflects intended usage
• js-comint-setup-module-paths removed, functionality merged into js-comint-start-or-switch-to-repl
• js-comint-start-or-switch-to-repl now creates a temporary environment rather than doing setenv every run
• Change package-requires to emacs 28.1 to use with-environment-variables macro
• js-comint-repl now sets the command and uses nvm without using a prefix arg
  Previously these were included in the when clause within the interactive call, meaning that they were almost never used.
  This probably was an indentation/nesting error. The effect is that when cmd is given, the global js-comint-program-command will be updated.

Questions

• Is the new behaviour of js-comint-repl correct/sensible?
  Check use with and without nvm
• Is the emacs 28.1 constraint acceptable?
  (IMO emacs LTS version is 29, so it's ok)

Specifics

After enabling lexical binding in the main file these functions had "unused lexical variable" warnings

• js-comint-filter-output (string)
  Fixed by marking the arg as ignored.
• js-comint-repl (cmd)
  Fixed by moving the "set command" logic out of the interactive call.

As noted above, the behaviour of js-comint-repl (cmd) is now sticky:

(setq js-comint-program-command "node")
(js-repl "custom-node") ;; uses custom-node
js-comint-program-command ;; custom-node
(js-repl) ;; uses custom-node

If nvm is used:

(js-comint-select-node-version) ;; manually select node-123
(js-repl "custom-node") ;; uses custom-node, prints message warning nvm is disabled
js-comint-program-command ;; custom-node
js-use-nvm ;; nil
(js-repl)  ;; uses custom-node

Previously, these effects only happened when js-comint-repl was called interactively with a prefix argument.

Also, within js-comint-repl the variable js-comint-module-paths is dynamically let-bound to temporarily change its value (used in js-comint-setup-module-paths). This required more extensive changes to fix.

Since js-comint-setup-module-paths sets the environment permanently using setenv, the dynamic binding creates a bug where every new visited node_modules is added to the NODE_PATH for each successive call to js-comint-repl. Instead I changed to using a local environment for each call to js-comint-start-or-switch-to-repl.

Using a local environment uncovers a different problem:

(js-comint-repl) ;; adds /local/node_modules to NODE_PATH
;; calls js-comint-start-or-switch-to-repl
(js-comint-reset-repl) ;; never calls js-comint-suggest-path
;; calls js-comint-start-or-switch-to-repl

When NODE_PATH was set globally, this was fine as the old path was still present. But now the environment is reset for each call to js-comint-start-or-switch-to-repl. Better for the dynamic setting behaviour to move from js-comint-repl to js-comint-start-or-switch-to-repl so that successive calls still use the expected node_modules.

[redguardtoo]

Thanks