From fea3b6d81ace6a23bf990602731ba31902c26375 Mon Sep 17 00:00:00 2001
From: Tom Lau <tomandfatboy@gmail.com>
Date: Mon, 1 Jul 2024 09:30:43 +0800
Subject: [PATCH 1/3] perf: Optimize work distribution in multi-threaded
 `--check`

The current hash function used to distribute work seems not perfect.
We can actually use round robin to distribute after sorting file list.
---
 script/cli/check_worker.lua | 13 ++-----------
 1 file changed, 2 insertions(+), 11 deletions(-)

diff --git a/script/cli/check_worker.lua b/script/cli/check_worker.lua
index 23c34b2c5..822c83dc6 100644
--- a/script/cli/check_worker.lua
+++ b/script/cli/check_worker.lua
@@ -43,15 +43,6 @@ local checkLevel = define.DiagnosticSeverity[CHECKLEVEL] or define.DiagnosticSev
 
 util.enableCloseFunction()
 
--- Hash function used to distribute work.
-local function hashString(str)
-    local hash = 0
-    for i = 1, #str do
-        hash = (hash * 37 & 0xFFFFFFFF) + str:byte(i, i)
-    end
-    return hash
-end
-
 local lastClock = os.clock()
 local results = {}
 
@@ -109,9 +100,9 @@ xpcall(lclient.start, errorhandler, lclient, function (client)
 
     local uris = files.getChildFiles(rootUri)
     local max  = #uris
+    table.sort(uris)    -- sort file list to ensure the work distribution order across multiple threads
     for i, uri in ipairs(uris) do
-        local hash = hashString(uri) % numThreads + 1
-        if hash == threadId then
+        if (i % numThreads + 1) == threadId then
             files.open(uri)
             diag.doDiagnostic(uri, true)
             -- Print regularly but always print the last entry to ensure that logs written to files don't look incomplete.

From cad34b796b14c1e9d9ae062339d7e9d4cd18cc22 Mon Sep 17 00:00:00 2001
From: Tom Lau <tomandfatboy@gmail.com>
Date: Mon, 1 Jul 2024 09:40:16 +0800
Subject: [PATCH 2/3] perf: Optimize undefined-field check early break logic

The current early break only wants to check if there are any definition.
There is no need to fetch the full definitions list.
We can early break as soon as we found the 1st one.
---
 script/core/diagnostics/undefined-field.lua |  2 +-
 script/vm/def.lua                           | 39 +++++++++++++++++++++
 2 files changed, 40 insertions(+), 1 deletion(-)

diff --git a/script/core/diagnostics/undefined-field.lua b/script/core/diagnostics/undefined-field.lua
index 4fd55966d..ab5d4d544 100644
--- a/script/core/diagnostics/undefined-field.lua
+++ b/script/core/diagnostics/undefined-field.lua
@@ -21,7 +21,7 @@ return function (uri, callback)
     local function checkUndefinedField(src)
         await.delay()
 
-        if #vm.getDefs(src) > 0 then
+        if vm.hasDef(src) then
             return
         end
         local node = src.node
diff --git a/script/vm/def.lua b/script/vm/def.lua
index 5388a3849..669d39c25 100644
--- a/script/vm/def.lua
+++ b/script/vm/def.lua
@@ -92,3 +92,42 @@ function vm.getDefs(source)
 
     return results
 end
+
+local HAS_DEF_ERR = {}  -- the error object for comparing
+local function checkHasDef(checkFunc, source, pushResult)
+    local _, err = pcall(checkFunc, source, pushResult)
+    return err == HAS_DEF_ERR
+end
+
+---@param source parser.object
+function vm.hasDef(source)
+    local mark = {}
+    local hasLocal
+    local function pushResult(src)
+        if src.type == 'local' then
+            if hasLocal then
+                return
+            end
+            hasLocal = true
+            if  source.type ~= 'local'
+            and source.type ~= 'getlocal'
+            and source.type ~= 'setlocal'
+            and source.type ~= 'doc.cast.name' then
+                return
+            end
+        end
+        if not mark[src] then
+            mark[src] = true
+            if guide.isAssign(src)
+            or guide.isLiteral(src) then
+                -- break out on 1st result using error() with a unique error object
+                error(HAS_DEF_ERR)
+            end
+        end
+    end
+
+    return checkHasDef(searchBySimple, source, pushResult)
+        or checkHasDef(searchByLocalID, source, pushResult)
+        or checkHasDef(vm.compileByNodeChain, source, pushResult)
+        or checkHasDef(searchByNode, source, pushResult)
+end

From f58d0bade94622ac80c89250a31f38195bf99756 Mon Sep 17 00:00:00 2001
From: Tom Lau <tomandfatboy@gmail.com>
Date: Mon, 1 Jul 2024 09:42:02 +0800
Subject: [PATCH 3/3] doc: Update changelog

---
 changelog.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/changelog.md b/changelog.md
index ef4a40179..d777fdc05 100644
--- a/changelog.md
+++ b/changelog.md
@@ -5,6 +5,7 @@
 * `NEW` Add postfix snippet for `unpack`
 * `FIX` `diagnostics.severity` defaulting to "Warning" when run using `--check` [#2730](https://github.com/LuaLS/lua-language-server/issues/2730)
 * `NEW` Add support for lambda style functions, `|paramList| expr` is syntactic sugar for `function(paramList) return expr end` 
+* `CHG` Improve performance of multithreaded `--check` and `undefined-field` diagnostic
 
 ## 3.9.3
 `2024-6-11`