Add julia.experimental.loweringLint setting

src/languageserverinstance.jl

@@ -66,6 +66,10 @@
     enable_dynamic_indexing::Bool
     max_concurrent_indexing_processes::Int
     enable_workspace_environment_resolution::Bool
+    # Experiment flag: JuliaLowering-backed unused-binding lint rules
+    # (`julia.experimental.loweringLint`); forwarded to
+    # `JuliaWorkspaces.set_lowering_lint!`.
+    lowering_lint::Bool
 
     clientcapability_workspace_diagnostic_refreshsupport::Bool
 
@@ -99,7 +103,7 @@
 
     trace_value::Threads.Atomic{Int}
 
     function LanguageServerInstance(@nospecialize(pipe_in), @nospecialize(pipe_out), env_path="", err_handler=nothing, symserver_store_path=nothing, julia_exe::Union{NamedTuple{(:path,:version),Tuple{String,VersionNumber}},Nothing}=nothing)
         endpoint = JSONRPC.JSONRPCEndpoint(pipe_in, pipe_out)
 
         combined_queue = Channel{Any}(Inf)
@@ -130,6 +134,7 @@
             4,
             true,
             false,
+            false,
             Dict{URI,Int}(),
             Dict{URI,JuliaWorkspaces.TextFile}(),
             Set{URI}(),
@@ -170,7 +175,7 @@
     try
         if USE_REVISE[] && isdefined(Main, :Revise)
             try
                 Main.Revise.revise()
             catch e
                 @warn "Reloading with Revise failed" exception = e
             end
@@ -186,7 +191,7 @@
 end
 
 function request_wrapper(func, server::LanguageServerInstance)
     return function (conn, params, token)
         if server.shutdown_requested
             # it's fine to always return a value here, even for notifications, because
             # JSONRPC discards it anyways in that case

src/requests/init.jl

@@ -232,6 +232,7 @@ function initialized_notification(params::InitializedParams, server::LanguageSer
             ConfigurationItem(missing, "julia.enableDynamicIndexing"),
             ConfigurationItem(missing, "julia.maxConcurrentIndexingProcesses"),
             ConfigurationItem(missing, "julia.enableWorkspaceEnvironmentResolution"),
+            ConfigurationItem(missing, "julia.experimental.loweringLint"),
         ]))
 
         server.completion_mode = Symbol(something(response[1], :import))
@@ -243,6 +244,7 @@ function initialized_notification(params::InitializedParams, server::LanguageSer
         server.enable_dynamic_indexing = something(response[7], true)
         server.max_concurrent_indexing_processes = something(response[8], 4)
         server.enable_workspace_environment_resolution = something(response[9], true)
+        server.lowering_lint = something(response[10], false)
     end
 
     # Construct JuliaWorkspace now that configuration values are available.
@@ -261,6 +263,9 @@ function initialized_notification(params::InitializedParams, server::LanguageSer
         max_concurrent_djps=server.max_concurrent_indexing_processes,
         resolve_workspace_environments=server.enable_workspace_environment_resolution,
     )
+    # Apply the experiment flag from the initial configuration pull (the JW
+    # default is off, so only an explicit opt-in needs forwarding).
+    server.lowering_lint && JuliaWorkspaces.set_lowering_lint!(server.workspace, true)
 
     # A single "bootstrap" bar covers the synchronous load below, which is
     # otherwise silent (the first indexing bar only appears once add_files!

src/requests/workspace.jl

@@ -117,6 +117,7 @@ function request_julia_config(server::LanguageServerInstance, conn)
         ConfigurationItem(missing, "julia.enableDynamicIndexing"),
         ConfigurationItem(missing, "julia.maxConcurrentIndexingProcesses"),
         ConfigurationItem(missing, "julia.enableWorkspaceEnvironmentResolution"),
+        ConfigurationItem(missing, "julia.experimental.loweringLint"),
     ]))
 
     new_completion_mode = Symbol(something(response[1], :import))
@@ -129,12 +130,37 @@ function request_julia_config(server::LanguageServerInstance, conn)
     server.inlay_hints_variable_types = inlayHintsVariableTypes
     server.inlay_hints_parameter_names = inlayHintsParameterNames
 
-    # Store new settings on server; JW is not reconfigured at runtime (future work).
+    # Store new settings on server; JW is not reconfigured at runtime (future
+    # work), with the exception of the lowering-lint experiment flag below.
     server.symbolcache_download = something(response[5], false)
     server.symbolcache_upstream = something(response[6], JuliaWorkspaces.DEFAULT_SYMBOLCACHE_UPSTREAM)
     server.enable_dynamic_indexing = something(response[7], true)
     server.max_concurrent_indexing_processes = something(response[8], 4)
     server.enable_workspace_environment_resolution = something(response[9], true)
+
+    set_lowering_lint!(server, something(response[10], false))
+end
+
+"""
+    set_lowering_lint!(server::LanguageServerInstance, enabled::Bool)
+
+Apply the `julia.experimental.loweringLint` setting: forward it to the
+workspace (switching the unused-binding lint rules between the StaticLint and
+JuliaLowering engines) and republish diagnostics so the change is visible
+without further edits.
+"""
+function set_lowering_lint!(server::LanguageServerInstance, enabled::Bool)
+    server.lowering_lint == enabled && return
+    server.lowering_lint = enabled
+    server.workspace === nothing && return
+
+    JuliaWorkspaces.set_lowering_lint!(server.workspace, enabled)
+
+    # Push-mode clients get a diffed sweep; pull-mode clients a refresh request.
+    schedule_publish_sweep!(server)
+    if server.clientcapability_workspace_diagnostic_refreshsupport
+        JSONRPC.send(server.jr_endpoint, workspace_diagnosticRefresh_request_type, nothing)
+    end
 end
 
 function gc_files_from_workspace(server::LanguageServerInstance)

test/test_lowering_lint_config.jl

@@ -0,0 +1,27 @@
+@testitem "julia.experimental.loweringLint switches the lint engine" setup=[TestSetup, SharedServer] begin
+    using LanguageServer: set_lowering_lint!
+    import JuliaWorkspaces
+
+    settestdoc("function f(x)\n    unused_local = 1\n    return x\nend\n")
+
+    unused_from_lowering() = any(
+        d -> d.code === :unused_binding && d.source == "JuliaWorkspaces.jl",
+        JuliaWorkspaces.get_diagnostic(server.workspace, uri"untitled:testdoc"))
+
+    # Off by default: nothing from the lowering producer.
+    @test server.lowering_lint == false
+    @test !unused_from_lowering()
+
+    set_lowering_lint!(server, true)
+    @test server.lowering_lint == true
+    @test unused_from_lowering()
+
+    # Idempotent and reversible.
+    set_lowering_lint!(server, true)
+    @test unused_from_lowering()
+    set_lowering_lint!(server, false)
+    @test server.lowering_lint == false
+    @test !unused_from_lowering()
+
+    closetestdoc()
+end