Fix inconsistencies and broken key bindings in the Rust layer (syl20b…

…nr#16217)

* [rust] Resurrect rust-backend variable

rust-backend was removed but is still meaningful (needs to be set to
the symbol lsp in order for LSP support to be enabled).

This commit restores the variable to config.el and removes boundp
checks because it will always be bound now (except in layers.el which
is loaded before config.el).

* [rust] Fully remove support for unmaintained rls backend

* [rust] Bind SPC m c . to rustic-cargo-run-rerun

This command has different behavior than cargo-process-repeat (the
previous meaning of this binding), but it is still a reasonable
binding and is the most similar command that exists in the rustic
package.

* [rust] Fix wrong command name

* [rust] Remove wrapper commands for package cargo

This package was removed in the Rust layer overhaul, so these commands
are not used anywhere.  In fact, the reloading behavior cannot easily
be implemented with rustic, because rustic runs `cargo add` and the
like in a compilation-mode buffer rather than synchronously.

As a result, we also remove references to automatically reloading the
workspace in rust-analyzer and the corresponding config variable.

* [rust] Remove unnecessary post-init stage

Layer rust owns package rustic, so there is no need to use post-init.

* [rust] Ensure rustic-mode key bindings are always available

Using :after in use-package prevents the :init forms from being
evaluated until lsp-mode and flycheck are loaded.  However, if the
user has disabled lsp-mode or flycheck, they should still be able to
use the rustic-cargo-* key bindings, so :after is not appropriate
here.

Instead, directly use with-eval-after-load where necessary for the
lsp-mode- and flycheck-specific configuration.

* [rust] Add rustic-clippy as an available flycheck checker

This just uncomments some code that was already there.  Not sure why
it was commented in the first place.

* [rust] Remove redundant progn

layers/+lang/rust/README.org

@@ -12,7 +12,7 @@
   - [[#lsp][LSP]]
     - [[#autocompletion][Autocompletion]]
     - [[#debugger-dap-integration][Debugger (dap integration)]]
-    - [[#automatically-reload-workspace][Automatically Reload Workspace]]
+    - [[#reloading-workspace][Reloading Workspace]]
   - [[#cargo][Cargo]]
     - [[#cargo-edit][cargo-edit]]
     - [[#cargo-outdated][cargo-outdated]]
@@ -45,20 +45,14 @@ To enable auto-completion, ensure that the =auto-completion= layer is enabled.
 *** Debugger (dap integration)
 To install the debug adapter you may run =M-x dap-gdb-lldb-setup= when you are on Linux or download it manually from [[https://marketplace.visualstudio.com/items?itemName=webfreak.debug][Native Debug]] and adjust =dap-gdb-lldb-path=.
 
-*** Automatically Reload Workspace
-When the LSP server is =rust-analyzer=, it may needs to reload the workspace to pickup changes made in =Cargo.toml=.
-You can call =spacemacs/lsp-rust-analyzer-reload-workspace=, which would be faster than restarting the LSP backend.
+*** Reloading Workspace
+By default, rust-analyzer will automatically reload the workspace
+after you make changes to =Cargo.toml= (such as adding dependencies).
 
-You can also set =cargo-process-reload-on-modify= to =t=, then it will automatically reload the workspace after
-one of the following is run:
-- =rustic-cargo-add=
-- =rustic-cargo-rm=
-- =rustic-cargo-upgrade=
-
-#+BEGIN_SRC elisp
-  (setq-default dotspacemacs-configuration-layers
-                 '(lsp :variables cargo-process-reload-on-modify t))
-#+END_SRC
+However, if =lsp-rust-analyzer-cargo-auto-reload= is set to nil, you
+will need to reload the workspace manually for the LSP to notice those
+changes.  You can call =spacemacs/lsp-rust-analyzer-reload-workspace=,
+which would be faster than restarting the LSP backend.
 
 ** Cargo
 [[http://doc.crates.io/index.html][Cargo]] is a project management command line tool for Rust. Installation
@@ -100,6 +94,7 @@ To enable automatic buffer formatting on save, set the variable =rustic-format-o
 |-------------+--------------------------------------------------------|
 | ~SPC m = =~ | reformat the buffer                                    |
 | ~SPC m b R~ | reload Rust-Analyzer workspace                         |
+| ~SPC m c .~ | rerun the default binary with the same arguments       |
 | ~SPC m c =~ | format all project files with rustfmt                  |
 | ~SPC m c a~ | add a new dependency with cargo-edit                   |
 | ~SPC m c c~ | compile project                                        |

layers/+lang/rust/config.el

@@ -25,5 +25,10 @@
 
 (spacemacs|define-jump-handlers rustic-mode)
 
-(defvar cargo-process-reload-on-modify nil
-  "When non-nil, reload workspace after a cargo-process command modifies Cargo.toml.")
+(defvar rust-backend (and (configuration-layer/layer-used-p 'lsp) 'lsp)
+  "The backend to use for completion.
+
+Currently, only `lsp' is supported.  It is automatically used if
+the `lsp' layer is enabled.
+
+If `nil', LSP support is disabled.")

layers/+lang/rust/funcs.el

@@ -36,20 +36,13 @@
   (message (concat "`lsp' layer is not installed, "
                    "please add `lsp' layer to your dotfile.")))
 
-(defun spacemacs/lsp-rust-switch-server ()
-  "Switch between rust-analyzer and rls."
-  (interactive)
-  (lsp-rust-switch-server)
-  (call-interactively 'lsp-workspace-restart))
-
 (defun spacemacs//rust-setup-lsp ()
   "Setup lsp backend."
   (if (configuration-layer/layer-used-p 'lsp)
       (progn
         (lsp-deferred)
         (spacemacs/declare-prefix-for-mode 'rustic-mode "ms" "switch")
         (spacemacs/set-leader-keys-for-major-mode 'rustic-mode
-          "ss" 'spacemacs/lsp-rust-switch-server
           (if lsp-use-upstream-bindings "wR" "bR") 'spacemacs/lsp-rust-analyzer-reload-workspace))
     (spacemacs//lsp-layer-not-installed-message)))
 
@@ -68,55 +61,12 @@
                                      :dap-compilation-dir "${workspaceFolder}"
                                      :cwd "${workspaceFolder}")))
 
-
-
 (defun spacemacs/lsp-rust-analyzer-reload-workspace ()
-  "Reload workspaces to pick up changes in Cargo.toml.
-Only applies to rust-analyzer, since rls automatically picks up changes already."
+  "Reload workspaces to pick up changes in Cargo.toml."
   (interactive)
-  (if (member 'rust-analyzer (spacemacs//lsp-client-server-id))
-      (progn
-        (lsp-rust-analyzer-reload-workspace)
-        (message "Reloaded workspace"))
-    (message "RLS reloads automatically, and doesn't require an explicit reload")))
-
-(when (configuration-layer/package-used-p 'cargo)
-  (defun spacemacs//cargo-maybe-reload ()
-    "Reload the workspace conditionally.
-When one of the following is true, it won't reload:
-- Backend is not rust-analyzer.
-- `cargo-process-reload-on-modify' is nil."
-    (when (and cargo-process-reload-on-modify
-               (and (boundp 'rust-backend)
-                    (eq rust-backend 'lsp))
-               (member 'rust-analyzer (spacemacs//lsp-client-server-id)))
-      (lsp-rust-analyzer-reload-workspace)))
-
-  (defun spacemacs/cargo-process-repeat ()
-    "Run last cargo process command, and conditionally reload the workspace."
-    (interactive)
-    (call-interactively 'cargo-process-repeat)
-    (when (member (car cargo-process-last-command)
-                  '("Add" "Remove" "Upgrade"))
-      (spacemacs//cargo-maybe-reload)))
-
-  (defun spacemacs/cargo-process-add ()
-    "Run the cargo add command, and conditionally reload the workspace."
-    (interactive)
-    (call-interactively 'cargo-process-add)
-    (spacemacs//cargo-maybe-reload))
-
-  (defun spacemacs/cargo-process-rm()
-    "Run the cargo rm command, and conditionally reload the workspace."
-    (interactive)
-    (call-interactively 'cargo-process-rm)
-    (spacemacs//cargo-maybe-reload))
-
-  (defun spacemacs/cargo-process-upgrade()
-    "Run the cargo upgrade command, and conditionally reload the workspace."
-    (interactive)
-    (call-interactively 'cargo-process-upgrade)
-    (spacemacs//cargo-maybe-reload)))
+  (when (member 'rust-analyzer (spacemacs//lsp-client-server-id))
+    (lsp-rust-analyzer-reload-workspace)
+    (message "Reloaded workspace")))
 
 
 ;; Misc

layers/+lang/rust/packages.el

@@ -36,8 +36,7 @@
   (spacemacs/counsel-gtags-define-keys-for-mode 'rustic-mode))
 
 (defun rust/pre-init-dap-mode ()
-  (when (and (boundp 'rust-backend)
-             (eq rust-backend 'lsp))
+  (when (eq rust-backend 'lsp)
     (add-to-list 'spacemacs--dap-supported-modes 'rustic-mode)
     (add-hook 'rustic-mode-local-vars-hook #'spacemacs//rust-setup-dap)))
 
@@ -47,42 +46,43 @@
 (defun rust/init-rustic ()
   (use-package rustic
     :defer t
-    :after (lsp-mode flycheck)
     :mode ("\\.rs\\'" . rustic-mode)
     :init
-    (progn
-      (add-hook 'rustic-mode-hook #'spacemacs//rust-setup-backend)
+    (add-hook 'rustic-mode-hook #'spacemacs//rust-setup-backend)
 
-      ;; (push 'rustic-clippy flycheck-checkers)
+    (spacemacs/declare-prefix-for-mode 'rustic-mode "mc" "cargo")
+    (spacemacs/declare-prefix-for-mode 'rustic-mode "mt" "tests")
+    (spacemacs/declare-prefix-for-mode 'rustic-mode "mg" "goto")
+    (spacemacs/declare-prefix-for-mode 'rustic-mode "mh" "help")
+    (spacemacs/declare-prefix-for-mode 'rustic-mode "m=" "format")
+    (spacemacs/set-leader-keys-for-major-mode 'rustic-mode
+      "c." 'rustic-cargo-run-rerun
+      "c=" 'rustic-cargo-fmt
+      "ca" 'rustic-cargo-add
+      "cc" 'rustic-cargo-build
+      "cC" 'rustic-cargo-clean
+      "cd" 'rustic-cargo-doc
+      "cs" 'rustic-doc-search
+      "ce" 'rustic-cargo-bench
+      "ci" 'rustic-cargo-init
+      "cl" 'rustic-cargo-clippy
+      "cf" 'rustic-cargo-clippy-fix
+      "cn" 'rustic-cargo-new
+      "co" 'rustic-cargo-outdated
+      "cr" 'rustic-cargo-rm
+      "cu" 'rustic-cargo-update
+      "cU" 'rustic-cargo-upgrade
+      "cv" 'rustic-cargo-check
+      "cx" 'rustic-cargo-run
+      "ta" 'rustic-cargo-test
+      "tt" 'rustic-cargo-current-test)
 
-      (spacemacs/declare-prefix-for-mode 'rustic-mode "mc" "cargo")
-      (spacemacs/declare-prefix-for-mode 'rustic-mode "mt" "tests")
-      (spacemacs/declare-prefix-for-mode 'rustic-mode "mg" "goto")
-      (spacemacs/declare-prefix-for-mode 'rustic-mode "mh" "help")
-      (spacemacs/declare-prefix-for-mode 'rustic-mode "m=" "format")
-      (spacemacs/set-leader-keys-for-major-mode 'rustic-mode
-        ;; Deactivated for now see https://github.com/syl20bnr/spacemacs/issues/16203 for details
-        ;; "c." 'spacemacs/rustic-cargo-repeat
-        "c=" 'rustic-cargo-fmt
-        "ca" 'rustic-cargo-add
-        "cc" 'rustic-cargo-build
-        "cC" 'rustic-cargo-clean
-        "cd" 'rustic-cargo-doc
-        "cs" 'rustic-cargo-doc-search
-        "ce" 'rustic-cargo-bench
-        "ci" 'rustic-cargo-init
-        "cl" 'rustic-cargo-clippy
-        "cf" 'rustic-cargo-clippy-fix
-        "cn" 'rustic-cargo-new
-        "co" 'rustic-cargo-outdated
-        "cr" 'spacemacs/rustic-cargo-rm
-        "cu" 'rustic-cargo-update
-        "cU" 'rustic-cargo-upgrade
-        "cv" 'rustic-cargo-check
-        "cx" 'rustic-cargo-run
-        "ta" 'rustic-cargo-test
-        "tt" 'rustic-cargo-current-test
+    (with-eval-after-load 'flycheck
+      (spacemacs/enable-flycheck 'rustic-mode)
+      (push 'rustic-clippy flycheck-checkers))
 
+    (with-eval-after-load 'lsp-mode
+      (spacemacs/set-leader-keys-for-major-mode 'rustic-mode
         "=j" 'lsp-rust-analyzer-join-lines
         "==" 'lsp-format-buffer
         "Ti" 'lsp-inlay-hints-mode
@@ -97,9 +97,6 @@
         "," 'lsp-rust-analyzer-rerun
         "."  'lsp-rust-analyzer-run))))
 
-(defun rust/post-init-rustic ()
-  (spacemacs/enable-flycheck 'rustic-mode))
-
 (defun rust/post-init-smartparens ()
   (with-eval-after-load 'smartparens
     ;; Don't pair lifetime specifiers