Proposal: make it easier to work with dotnet tools for C#/F#

This commit implements an approach proposed in #3906. Specifically, it provides
new control variables to make it possible to use C# and F# language servers
_either_ as global _or_ local dotnet tools. So far, I've done this by providing
boolean variables to control command construction, but I'm not attached to this
approach.

Closes #3906.

clients/lsp-csharp.el

@@ -120,13 +120,28 @@ Usually this is to be set in your .dir-locals.el on the project root directory."
   :group 'lsp-csharp-omnisharp
   :type 'file)
 
+
 (defcustom lsp-csharp-omnisharp-enable-decompilation-support
   nil
   "Decompile bytecode when browsing method metadata for types in assemblies.
 Otherwise only declarations for the methods are visible (the default)."
   :group 'lsp-csharp
   :type 'boolean)
 
+(defcustom lsp-csharp-csharpls-use-dotnet-tool t
+  "Whether to use a dotnet tool version of the expected C# language server; only available for csharp-ls"
+  :group 'lsp-csharp
+  :type 'boolean
+  :risky t)
+
+(defcustom lsp-csharp-csharpls-use-local-tool nil
+  "Whether to use csharp-ls as a global or local dotnet tool.
+
+Note: this variable has no effect if lsp-csharp-csharpls-use-dotnet-tool is nil."
+  :group 'lsp-csharp
+  :type 'boolean
+  :risky t)
+
 (lsp-dependency
  'omnisharp-roslyn
  `(:download :url lsp-csharp-omnisharp-roslyn-download-url
@@ -485,6 +500,15 @@ filename is returned so lsp-mode can display this file."
                   (with-temp-buffer (insert-file-contents metadata-file-name)
                                     (buffer-string))))))
 
+(defun lsp-csharp--cls-find-executable ()
+  (or (when lsp-csharp-csharpls-use-dotnet-tool
+        (-flatten (list "dotnet" (if lsp-csharp-csharpls-use-local-tool (list "tool" "run") "") "csharp-ls")))
+      (executable-find "csharp-ls")
+      ;; NOTE[gastove|2023-02-03] This approach might be remove-able if we
+      ;; standardize on going through the `dotnet' cli.
+      (f-join (or (getenv "USERPROFILE") (getenv "HOME"))
+              ".dotnet" "tools" "csharp-ls")))
+
 (defun lsp-csharp--cls-make-launch-cmd ()
   "Return command line to invoke csharp-ls."
 
@@ -504,16 +528,25 @@ filename is returned so lsp-mode can display this file."
 
                                (t nil)))
 
-        (csharp-ls-exec (or (executable-find "csharp-ls")
-                            (f-join (or (getenv "USERPROFILE") (getenv "HOME"))
-                                    ".dotnet" "tools" "csharp-ls")))
+        (csharp-ls-exec (lsp-csharp--cls-find-executable))
 
         (solution-file-params (when lsp-csharp-solution-file
                                 (list "-s" lsp-csharp-solution-file))))
     (append startup-wrapper
-            (list csharp-ls-exec)
+            (if (listp csharp-ls-exec)
+                csharp-ls-exec
+              (list csharp-ls-exec))
             solution-file-params)))
 
+(defun lsp-csharp--cls-test-csharp-ls-present ()
+  "Return non-nil if dotnet tool csharp-ls is installed as a dotnet tool."
+  (string-match-p "csharp-ls"
+                  (shell-command-to-string
+                   (if lsp-csharp-csharpls-use-local-tool
+                       "dotnet tool list"
+                     "dotnet tool list -g")))
+  )
+
 (defun lsp-csharp--cls-download-server (_client callback error-callback update?)
   "Install/update csharp-ls language server using `dotnet tool'.
 
@@ -522,7 +555,7 @@ Will update if UPDATE? is t"
   (lsp-async-start-process
    callback
    error-callback
-   "dotnet" "tool" (if update? "update" "install") "-g" "csharp-ls"))
+   "dotnet" "tool" (if update? "update" "install") (if lsp-csharp-csharpls-use-local-tool "" "-g") "csharp-ls"))
 
 (lsp-register-client
  (make-lsp-client :new-connection (lsp-stdio-connection #'lsp-csharp--cls-make-launch-cmd)

clients/lsp-fsharp.el

@@ -157,15 +157,6 @@ with test projects are not autoloaded by FSharpAutoComplete."
   :type 'boolean
   :package-version '(lsp-mode . "9.0.0"))
 
-(defun lsp-fsharp--fsac-install (_client callback error-callback update?)
-  "Install/update fsautocomplete language server using `dotnet tool'.
-Will invoke CALLBACK or ERROR-CALLBACK based on result. Will update if
-UPDATE? is t."
-  (lsp-async-start-process
-   callback
-   error-callback
-   "dotnet" "tool" (if update? "update" "install") "-g" "fsautocomplete"))
-
 (defcustom lsp-fsharp-use-dotnet-tool-for-fsac t
   "Run FsAutoComplete as a dotnet tool.
 
@@ -176,14 +167,39 @@ available, else the globally installed tool."
   :type 'boolean
   :risky t)
 
+
+(defcustom lsp-fsharp-use-dotnet-local-tool nil
+  "When running FsAutoComplete as a dotnet tool, use the local version.
+
+This variable will have no effect if
+`lsp-fsharp-use-dotnet-tool-for-fsac' is nil.
+
+This variable is risky as a buffer-local, and should instead be
+set per-project (e.g. in a .dir-locals.el at the root of a
+repository)."
+  :group 'lsp-fsharp
+  :type 'boolean
+  :risky t)
+
 (defcustom lsp-fsharp-workspace-extra-exclude-dirs '()
   "Additional directories to exclude from FsAutoComplete workspace loading / discovery."
   :group 'lsp-fsharp
   :type 'lsp-string-vector)
 
+(defun lsp-fsharp--fsac-install (_client callback error-callback update?)
+  "Install/update fsautocomplete language server using `dotnet tool'.
+Will invoke CALLBACK or ERROR-CALLBACK based on result. Will update if
+UPDATE? is t."
+  (lsp-async-start-process
+   callback
+   error-callback
+   "dotnet" "tool" (if update? "update" "install") (when lsp-fsharp-use-dotnet-local-tool "-g") "fsautocomplete"))
+
 (defun lsp-fsharp--fsac-cmd ()
   "The location of fsautocomplete executable."
-  (or (-let [maybe-local-executable (expand-file-name "fsautocomplete" lsp-fsharp-server-install-dir)]
+  (or (when lsp-fsharp-use-dotnet-tool-for-fsac
+        (list "dotnet" (if lsp-fsharp-use-dotnet-local-tool "" "tool") "run" "fsautocomplete"))
+      (-let [maybe-local-executable (expand-file-name "fsautocomplete" lsp-fsharp-server-install-dir)]
         (when (f-exists-p maybe-local-executable)
           maybe-local-executable))
       (executable-find "fsautocomplete")
@@ -214,14 +230,22 @@ available, else the globally installed tool."
                                (t nil)))
         (fsautocomplete-exec (lsp-fsharp--fsac-cmd)))
     (append startup-wrapper
-            (list fsautocomplete-exec)
+            (if (listp fsautocomplete-exec)
+                fsautocomplete-exec
+              (list fsautocomplete-exec))
             lsp-fsharp-server-args)))
 
 (defun lsp-fsharp--test-fsautocomplete-present ()
   "Return non-nil if dotnet tool fsautocomplete is installed globally."
   (if lsp-fsharp-use-dotnet-tool-for-fsac
-      (string-match-p "fsautocomplete"
-                      (shell-command-to-string "dotnet tool list -g"))
+      (-let* ((cmd-str (if lsp-fsharp-use-dotnet-local-tool
+                           "dotnet tool list"
+                         "dotnet tool list -g"))
+              (res (string-match-p "fsautocomplete"
+                                  (shell-command-to-string cmd-str))))
+        (if res res
+          (error "Failed to locate fsautocomplete binary; due to lsp-fsharp-use-dotnet-local-tool == %s, checked with command %s" lsp-fsharp-use-dotnet-local-tool cmd-str)))
+
     (f-exists? (lsp-fsharp--fsac-cmd))))
 
 (defun lsp-fsharp--project-list (workspace)