[clang-tools-extra] [clangd] Implement LSP 3.17 positionEncoding (PR #142903)

[kadir çetinkaya via cfe-commits]

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@@ -497,6 +497,12 @@ bool fromJSON(const llvm::json::Value &Params, ClientCapabilities &R,
       if (auto Cancel = StaleRequestSupport->getBoolean("cancel"))
         R.CancelsStaleRequests = *Cancel;
     }
+    if (auto *OffsetEncoding = General->get("positionEncodings")) {
+      R.offsetEncoding.emplace();
+      if (!fromJSON(*OffsetEncoding, *R.offsetEncoding,
+                    P.field("general").field("positionEncodings")))
+        return false;
+    }
   }
   if (auto *OffsetEncoding = O->get("offsetEncoding")) {
     R.offsetEncoding.emplace();
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kadircet wrote:

can we log a warning if we're overwriting general capability with a clangd extension here, and also a deprecation message, asking clients to use general capability instead?

we should also mention this in release notes here, and update clangd docs https://clangd.llvm.org/extensions#utf-8-offsets, repo is at https://github.com/llvm/clangd-www/pulls.

https://github.com/llvm/llvm-project/pull/142903