[clang-tools-extra] [clangd] Add `HeaderInsertion` yaml config option (PR #128503)

[Nathan Ridge via cfe-commits]

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@@ -151,6 +151,15 @@ struct Config {
     ArgumentListsPolicy ArgumentLists = ArgumentListsPolicy::FullPlaceholders;
   } Completion;
 
+  enum class HeaderInsertionPolicy {
+    IWYU,       // Include what you use
+    NeverInsert // Never insert headers as part of code completion
+  };
+
+  struct {
+    HeaderInsertionPolicy Policy = HeaderInsertionPolicy::IWYU;
+  } HeaderInsertion;
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HighCommander4 wrote:

Since header insertion is a side effect of accepting of code completion proposal, it would make sense to have this option under `Completion` rather than at the top level.

https://github.com/llvm/llvm-project/pull/128503