#3600 Implement pull model with Neovim Client

Implement the diagnostics pull model with the LSP Neovim client. We
must handle messages a little different and tweak client capabilities
for pull diagnostics to work through the Neovim client.

Author: w0rp

autoload/ale/lsp_linter.vim

@@ -100,7 +100,7 @@ endfunction
 " Handle LSP diagnostics for a given URI.
 " The special value 'unchanged' can be used for diagnostics to indicate
 " that diagnostics haven't changed since we last checked.
-function! s:HandleLSPDiagnostics(conn_id, uri, diagnostics) abort
+function! ale#lsp_linter#HandleLSPDiagnostics(conn_id, uri, diagnostics) abort
     let l:linter = get(s:lsp_linter_map, a:conn_id)
 
     if empty(l:linter)
@@ -233,14 +233,14 @@ function! ale#lsp_linter#HandleLSPResponse(conn_id, response) abort
         let l:uri = a:response.params.uri
         let l:diagnostics = a:response.params.diagnostics
 
-        call s:HandleLSPDiagnostics(a:conn_id, l:uri, l:diagnostics)
+        call ale#lsp_linter#HandleLSPDiagnostics(a:conn_id, l:uri, l:diagnostics)
     elseif has_key(s:diagnostic_uri_map, get(a:response, 'id'))
         let l:uri = remove(s:diagnostic_uri_map, a:response.id)
         let l:diagnostics = a:response.result.kind is# 'unchanged'
         \   ? 'unchanged'
         \   : a:response.result.items
 
-        call s:HandleLSPDiagnostics(a:conn_id, l:uri, l:diagnostics)
+        call ale#lsp_linter#HandleLSPDiagnostics(a:conn_id, l:uri, l:diagnostics)
     elseif l:method is# 'window/showMessage'
         call ale#lsp_window#HandleShowMessage(
         \   s:lsp_linter_map[a:conn_id].name,

lua/ale/lsp.lua

@@ -38,13 +38,36 @@ module.start = function(config)
         -- functions so all of the functionality in ALE works.
         ["textDocument/publishDiagnostics"] = function(err, result, _, _)
             if err == nil then
-                vim.fn["ale#lsp_linter#HandleLSPResponse"](config.name, {
-                    jsonrpc = "2.0",
-                    method = "textDocument/publishDiagnostics",
-                    params = result
-                })
+                vim.fn["ale#lsp_linter#HandleLSPDiagnostics"](
+                    config.name,
+                    result.uri,
+                    result.diagnostics
+                )
             end
-        end
+        end,
+        -- Handle pull model diagnostic data.
+        ["textDocument/diagnostic"] = function(err, result, request, _)
+            if err == nil then
+                local diagnostics
+
+                if result.kind == "unchanged" then
+                    diagnostics = "unchanged"
+                else
+                    diagnostics = result.items
+                end
+
+                vim.fn["ale#lsp_linter#HandleLSPDiagnostics"](
+                    config.name,
+                    request.params.textDocument.uri,
+                    diagnostics
+                )
+            end
+        end,
+        -- When the pull model is enabled we have to handle and return
+        -- some kind of data for a server diagnostic refresh request.
+        ["workspace/diagnostic/refresh"] = function()
+            return {}
+        end,
     }
 
     config.on_init = function(client, _)
@@ -70,6 +93,16 @@ module.start = function(config)
         return vim.fn["ale#lsp#GetLanguage"](config.name, bufnr)
     end
 
+    local capabilities = vim.lsp.protocol.make_client_capabilities()
+
+    -- Language servers like Pyright do not enable the diagnostics pull model
+    -- unless dynamicRegistration is enabled for diagnostics.
+    if capabilities.textDocument.diagnostic ~= nil then
+        capabilities.textDocument.diagnostic.dynamicRegistration = true
+        config.capabilities = capabilities
+    end
+
+    ---@diagnostic disable-next-line: missing-fields
     return vim.lsp.start(config, {
         attach = false,
         silent = true,
@@ -93,6 +126,10 @@ end
 module.send_message = function(args)
     local client = vim.lsp.get_client_by_id(args.client_id)
 
+    if client == nil then
+        return 0
+    end
+
     if args.is_notification then
         -- For notifications we send a request and expect no direct response.
         local success = client.notify(args.method, args.params)

test/lua/ale_lsp_spec.lua

@@ -6,6 +6,7 @@ describe("ale.lsp.start", function()
     local rpc_connect_calls
     local vim_fn_calls
     local defer_calls
+    local nvim_default_capabilities
 
     setup(function()
         _G.vim = {
@@ -21,7 +22,7 @@ describe("ale.lsp.start", function()
                             return "python"
                         end
 
-                        if key ~= "ale#lsp_linter#HandleLSPResponse"
+                        if key ~= "ale#lsp_linter#HandleLSPDiagnostics"
                         and key ~= "ale#lsp#UpdateCapabilities"
                         and key ~= "ale#lsp#CallInitCallbacks"
                         then
@@ -49,6 +50,11 @@ describe("ale.lsp.start", function()
 
                     return 42
                 end,
+                protocol = {
+                    make_client_capabilities = function()
+                        return nvim_default_capabilities
+                    end,
+                },
             },
         }
     end)
@@ -62,6 +68,9 @@ describe("ale.lsp.start", function()
         rpc_connect_calls = {}
         vim_fn_calls = {}
         defer_calls = {}
+        nvim_default_capabilities = {
+            textDocument = {},
+        }
     end)
 
     it("should start lsp programs with the correct arguments", function()
@@ -148,6 +157,24 @@ describe("ale.lsp.start", function()
         eq({{"ale#lsp#GetLanguage", "server:/code", 347}}, vim_fn_calls)
     end)
 
+    it("should enable dynamicRegistration for the pull model", function()
+        nvim_default_capabilities = {textDocument = {diagnostic = {}}}
+
+        lsp.start({name = "server:/code"})
+        eq(1, #start_calls)
+
+        eq(
+            {
+                textDocument = {
+                    diagnostic = {
+                        dynamicRegistration = true,
+                    },
+                },
+            },
+            start_calls[1][1].capabilities
+        )
+    end)
+
     it("should initialize clients with ALE correctly", function()
         lsp.start({name = "server:/code"})
 
@@ -185,39 +212,150 @@ describe("ale.lsp.start", function()
             handler_names[key] = true
         end
 
-        eq({["textDocument/publishDiagnostics"] = true}, handler_names)
+        eq({
+            ["textDocument/publishDiagnostics"] = true,
+            ["textDocument/diagnostic"] = true,
+            ["workspace/diagnostic/refresh"] = true,
+        }, handler_names)
+    end)
+
+    it("should handle push model published diagnostics", function()
+        lsp.start({name = "server:/code"})
+
+        eq(1, #start_calls)
+
+        local handlers = start_calls[1][1].handlers
+
+        eq("function", type(handlers["textDocument/publishDiagnostics"]))
 
         handlers["textDocument/publishDiagnostics"](nil, {
-            {
-                lnum = 1,
-                end_lnum = 2,
-                col = 3,
-                end_col = 5,
-                severity = 1,
-                code = "123",
-                message = "Warning message",
+            uri = "file://code/foo.py",
+            diagnostics = {
+                {
+                    lnum = 1,
+                    end_lnum = 2,
+                    col = 3,
+                    end_col = 5,
+                    severity = 1,
+                    code = "123",
+                    message = "Warning message",
+                }
             },
         })
 
         eq({
             {
-                "ale#lsp_linter#HandleLSPResponse",
+                "ale#lsp_linter#HandleLSPDiagnostics",
                 "server:/code",
+                "file://code/foo.py",
                 {
-                    jsonrpc = "2.0",
-                    method = "textDocument/publishDiagnostics",
-                    params = {
-                        {
-                            lnum = 1,
-                            end_lnum = 2,
-                            col = 3,
-                            end_col = 5,
-                            severity = 1,
-                            code = "123",
-                            message = "Warning message",
-                        },
+                    {
+                        lnum = 1,
+                        end_lnum = 2,
+                        col = 3,
+                        end_col = 5,
+                        severity = 1,
+                        code = "123",
+                        message = "Warning message",
+                    },
+                },
+            },
+        }, vim_fn_calls)
+    end)
+
+    it("should respond to workspace diagnostic refresh requests", function()
+        lsp.start({name = "server:/code"})
+
+        eq(1, #start_calls)
+
+        local handlers = start_calls[1][1].handlers
+
+        eq("function", type(handlers["workspace/diagnostic/refresh"]))
+
+        eq({}, handlers["workspace/diagnostic/refresh"]())
+    end)
+
+    it("should handle pull model diagnostics", function()
+        lsp.start({name = "server:/code"})
+
+        eq(1, #start_calls)
+
+        local handlers = start_calls[1][1].handlers
+
+        eq("function", type(handlers["textDocument/diagnostic"]))
+
+        handlers["textDocument/diagnostic"](
+            nil,
+            {
+                kind = "full",
+                items = {
+                    {
+                        lnum = 1,
+                        end_lnum = 2,
+                        col = 3,
+                        end_col = 5,
+                        severity = 1,
+                        code = "123",
+                        message = "Warning message",
                     }
-                }
+                },
+            },
+            {
+                params = {
+                    textDocument = {
+                        uri = "file://code/foo.py",
+                    },
+                },
+            }
+        )
+
+        eq({
+            {
+                "ale#lsp_linter#HandleLSPDiagnostics",
+                "server:/code",
+                "file://code/foo.py",
+                {
+                    {
+                        lnum = 1,
+                        end_lnum = 2,
+                        col = 3,
+                        end_col = 5,
+                        severity = 1,
+                        code = "123",
+                        message = "Warning message",
+                    },
+                },
+            },
+        }, vim_fn_calls)
+    end)
+
+    it("should handle unchanged pull model diagnostics", function()
+        lsp.start({name = "server:/code"})
+
+        eq(1, #start_calls)
+
+        local handlers = start_calls[1][1].handlers
+
+        eq("function", type(handlers["textDocument/diagnostic"]))
+
+        handlers["textDocument/diagnostic"](
+            nil,
+            {kind = "unchanged"},
+            {
+                params = {
+                    textDocument = {
+                        uri = "file://code/foo.py",
+                    },
+                },
+            }
+        )
+
+        eq({
+            {
+                "ale#lsp_linter#HandleLSPDiagnostics",
+                "server:/code",
+                "file://code/foo.py",
+                "unchanged",
             },
         }, vim_fn_calls)
     end)