feat(julials): improve project detection and simplify launch (#1079)

* Simplify LanguageServer.jl launch command (https://github.com/julia-vscode/SymbolServer.jl/issues/54#issuecomment-643667218) 
* respect JULIA_PROJECT and JULIA_LOAD_PATH

1 files changed, 46 insertions, 16 deletions

diff --git a/lua/lspconfig/julials.lua b/lua/lspconfig/julials.lua
index bdf92b3a..e92d17c6 100644
--- a/lua/lspconfig/julials.lua
+++ b/lua/lspconfig/julials.lua
@@ -7,16 +7,31 @@ local cmd = {
   '--history-file=no',
   '-e',
   [[
-    using Pkg;
+    using Pkg
     Pkg.instantiate()
-    using LanguageServer; using SymbolServer;
+    using LanguageServer
     depot_path = get(ENV, "JULIA_DEPOT_PATH", "")
-    project_path = dirname(something(Base.current_project(pwd()), Base.load_path_expand(LOAD_PATH[2])))
-    # Make sure that we only load packages from this environment specifically.
-    @info "Running language server" env=Base.load_path()[1] pwd() project_path depot_path
-    server = LanguageServer.LanguageServerInstance(stdin, stdout, project_path, depot_path);
-    server.runlinter = true;
-    run(server);
+    project_path = let
+        dirname(something(
+            ## 1. Finds an explicitly set project (JULIA_PROJECT)
+            Base.load_path_expand((
+                p = get(ENV, "JULIA_PROJECT", nothing);
+                p === nothing ? nothing : isempty(p) ? nothing : p
+            )),
+            ## 2. Look for a Project.toml file in the current working directory,
+            ##    or parent directories, with $HOME as an upper boundary
+            Base.current_project(),
+            ## 3. First entry in the load path
+            get(Base.load_path(), 1, nothing),
+            ## 4. Fallback to default global environment,
+            ##    this is more or less unreachable
+            Base.load_path_expand("@v#.#"),
+        ))
+    end
+    @info "Running language server" VERSION pwd() project_path depot_path
+    server = LanguageServer.LanguageServerInstance(stdin, stdout, project_path, depot_path)
+    server.runlinter = true
+    run(server)
   ]],
 }
 
@@ -57,16 +72,31 @@ require'lspconfig'.julials.setup{
         "--startup-file=no",
         "--history-file=no",
         "-e", [[
-          using Pkg;
+          using Pkg
           Pkg.instantiate()
-          using LanguageServer; using SymbolServer;
+          using LanguageServer
           depot_path = get(ENV, "JULIA_DEPOT_PATH", "")
-          project_path = dirname(something(Base.current_project(pwd()), Base.load_path_expand(LOAD_PATH[2])))
-          # Make sure that we only load packages from this environment specifically.
-          @info "Running language server" env=Base.load_path()[1] pwd() project_path depot_path
-          server = LanguageServer.LanguageServerInstance(stdin, stdout, project_path, depot_path);
-          server.runlinter = true;
-          run(server);
+          project_path = let
+              dirname(something(
+                  ## 1. Finds an explicitly set project (JULIA_PROJECT)
+                  Base.load_path_expand((
+                      p = get(ENV, "JULIA_PROJECT", nothing);
+                      p === nothing ? nothing : isempty(p) ? nothing : p
+                  )),
+                  ## 2. Look for a Project.toml file in the current working directory,
+                  ##    or parent directories, with $HOME as an upper boundary
+                  Base.current_project(),
+                  ## 3. First entry in the load path
+                  get(Base.load_path(), 1, nothing),
+                  ## 4. Fallback to default global environment,
+                  ##    this is more or less unreachable
+                  Base.load_path_expand("@v#.#"),
+              ))
+          end
+          @info "Running language server" VERSION pwd() project_path depot_path
+          server = LanguageServer.LanguageServerInstance(stdin, stdout, project_path, depot_path)
+          server.runlinter = true
+          run(server)
         \]\]
     };
       new_config.cmd = cmd