[clang-tools-extra] 4493a8a - [clangd] Make the --skip-preamble-build option take an enum (#229515)

[via cfe-commits]

Author: Tomáš Slanina
Date: 2026-10-25T18:14:52+08:00
New Revision: 4493a8a4132df15da3e985cdf285f6fbf5dce645

URL: https://github.com/llvm/llvm-project/commit/4493a8a4132df15da3e985cdf285f6fbf5dce645
DIFF: https://github.com/llvm/llvm-project/commit/4493a8a4132df15da3e985cdf285f6fbf5dce645.diff

LOG: [clangd] Make the --skip-preamble-build option take an enum (#229515)

Add a new value `never` allowing the preamble skipping to be
force-disabled, in addition to `modules` and `always`.

The default is `modules`, equivalent to the old behavior.

Closes #212403

Added: 
    

Modified: 
    clang-tools-extra/clangd/ClangdServer.cpp
    clang-tools-extra/clangd/ClangdServer.h
    clang-tools-extra/clangd/tool/ClangdMain.cpp

Removed: 
    


################################################################################
diff  --git a/clang-tools-extra/clangd/ClangdServer.cpp b/clang-tools-extra/clangd/ClangdServer.cpp
index 3d05b57fcad8ee..8535823abc5203 100644
--- a/clang-tools-extra/clangd/ClangdServer.cpp
+++ b/clang-tools-extra/clangd/ClangdServer.cpp
@@ -1221,7 +1221,17 @@ void ClangdServer::adjustParseInputs(ParseInputs &Inputs, PathRef File) const {
                                     : Context::current().clone());
     return ModulesManager->hasRequiredModules(File);
   };
-  Inputs.Opts.SkipPreambleBuild = SkipPreambleBuild || HasRequiredModules();
+
+  Inputs.Opts.SkipPreambleBuild = [&]() {
+    switch (SkipPreambleBuild) {
+    case SkipPreambleBuildPolicy::Never:
+      return false;
+    case SkipPreambleBuildPolicy::Modules:
+      return HasRequiredModules();
+    case SkipPreambleBuildPolicy::Always:
+      return true;
+    }
+  }();
 }
 
 } // namespace clangd

diff  --git a/clang-tools-extra/clangd/ClangdServer.h b/clang-tools-extra/clangd/ClangdServer.h
index 264ab7437c248c..ce3e66e4eb2866 100644
--- a/clang-tools-extra/clangd/ClangdServer.h
+++ b/clang-tools-extra/clangd/ClangdServer.h
@@ -98,6 +98,8 @@ class ClangdServer {
   createConfiguredContextProvider(const config::Provider *Provider,
                                   ClangdServer::Callbacks *);
 
+  enum class SkipPreambleBuildPolicy { Never, Modules, Always };
+
   struct Options {
     /// To process requests asynchronously, ClangdServer spawns worker threads.
     /// If this is zero, no threads are spawned. All work is done on the calling
@@ -191,8 +193,10 @@ class ClangdServer {
     // If true, parse emplace-like functions in the preamble.
     bool PreambleParseForwardingFunctions = true;
 
-    // If true, skip preamble build.
-    bool SkipPreambleBuild = false;
+    // If Always, discard preamble during update
+    // If Modules, only discard when modules are required
+    SkipPreambleBuildPolicy SkipPreambleBuild =
+        SkipPreambleBuildPolicy::Modules;
 
     /// Whether include fixer insertions for Objective-C code should use #import
     /// instead of #include.
@@ -513,7 +517,7 @@ class ClangdServer {
 
   bool PreambleParseForwardingFunctions = true;
 
-  bool SkipPreambleBuild = false;
+  SkipPreambleBuildPolicy SkipPreambleBuild = {};
 
   bool ImportInsertions = false;
 

diff  --git a/clang-tools-extra/clangd/tool/ClangdMain.cpp b/clang-tools-extra/clangd/tool/ClangdMain.cpp
index 25c987d9c29341..451495e1dbf1f1 100644
--- a/clang-tools-extra/clangd/tool/ClangdMain.cpp
+++ b/clang-tools-extra/clangd/tool/ClangdMain.cpp
@@ -519,12 +519,18 @@ opt<bool> PreambleParseForwardingFunctions{
     init(ParseOptions().PreambleParseForwardingFunctions),
 };
 
-opt<bool> SkipPreambleBuild{
+opt<ClangdServer::SkipPreambleBuildPolicy> SkipPreambleBuild{
     "skip-preamble-build",
     cat(Misc),
-    desc("If ture, skip preamble build"),
+    desc("Skip building the preamble"),
     Hidden,
-    init(ParseOptions().SkipPreambleBuild),
+    values(clEnumValN(ClangdServer::SkipPreambleBuildPolicy::Never, "never",
+                      "never skip"),
+           clEnumValN(ClangdServer::SkipPreambleBuildPolicy::Modules, "modules",
+                      "only if module use is encountered (default)"),
+           clEnumValN(ClangdServer::SkipPreambleBuildPolicy::Always, "always",
+                      "always skip")),
+    init(ClangdServer::Options().SkipPreambleBuild),
 };
 
 #if defined(__GLIBC__) && CLANGD_MALLOC_TRIM